Citation
Examining Seasonal Movement and Habitat Use Patterns of Adult Common Snook

Material Information

Title:
Examining Seasonal Movement and Habitat Use Patterns of Adult Common Snook
Creator:
Marcinkiewicz, Lauren L
Place of Publication:
[Gainesville, Fla.]
Florida
Publisher:
University of Florida
Publication Date:
Language:
english
Physical Description:
1 online resource (53 p.)

Thesis/Dissertation Information

Degree:
Master's ( M.S.)
Degree Grantor:
University of Florida
Degree Disciplines:
Fisheries and Aquatic Sciences
Committee Chair:
Pine, William
Committee Members:
Leber, Kenneth Miles
Frazer, Tom K.
Graduation Date:
12/14/2007

Subjects

Subjects / Keywords:
Aquatic habitats ( jstor )
Bayous ( jstor )
Bays ( jstor )
Creeks ( jstor )
Dredging ( jstor )
Fish ( jstor )
Habitat conservation ( jstor )
Mortality ( jstor )
Red tides ( jstor )
Seasons ( jstor )
Fisheries and Aquatic Sciences -- Dissertations, Academic -- UF
habitat, movement, snook
Sarasota Bay ( local )
Genre:
bibliography ( marcgt )
theses ( marcgt )
government publication (state, provincial, terriorial, dependent) ( marcgt )
born-digital ( sobekcm )
Electronic Thesis or Dissertation
Fisheries and Aquatic Sciences thesis, M.S.

Notes

Abstract:
The common snook, Centropomus undecimalis, is an ecologically and economically important estuarine dependent predatory fish species found throughout south Florida. Despite increasingly restrictive management actions over the past 50 years, common snook populations are thought to have declined. Possible reasons for this decline are high harvest rates and loss of essential habitat related to coastal development. I evaluated habitat use and movement patterns for adult snook in seasons with and without large-scale environmental (red tide blooms) and anthropogenic (dredging) disturbance events. The results of this study support much of the literature on snook life history while providing new behavioral information regarding movement, site fidelity, and habitat disturbances. This study provides important information for conservation management purposes and improves the understanding of direct and indirect effects of habitat threats associated with anthropogenic and environmental disturbances on snook populations. This understanding of habitat-species relationships is important because of the emphasis placed on managing habitat by various State and Federal agencies for the conservation of fish and wildlife resources. ( en )
General Note:
In the series University of Florida Digital Collections.
General Note:
Includes vita.
Bibliography:
Includes bibliographical references.
Source of Description:
Description based on online resource; title from PDF title page.
Source of Description:
This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Thesis:
Thesis (M.S.)--University of Florida, 2007.
Local:
Adviser: Pine, William.
Statement of Responsibility:
by Lauren L Marcinkiewicz.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
Copyright Marcinkiewicz, Lauren L. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Resource Identifier:
664030038 ( OCLC )
Classification:
LD1780 2007 ( lcc )

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Full Text

























To my mother, father, and sisters for their unconditional love and support.












- New Pass

-Bowlees Creek


32
30
28
26
24
22 -
20 -
18
16
14


I \


, ***


. r
*


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o b
o\ o\


Date



Figure 3-7. Average monthly water temperatures (oC) for an open bay area (New Pass) and a
creek habitat (Bowlees Creek) in Sarasota Bay, Florida.



80

S70



S50

S40

S30

S20





Creek Mangrove Open bay Pass

Habitat type


Figure 3-8. Habitat use (percent fish-days) at the original capture habitat and location for snook
(n=48). This graph is showing high site fidelity demonstrated by snook captured and
released at specific habitat types (creeks and open bay).










amount of VR2 coverage. This led to open bay becoming the smallest proportion of monitored

habitat, in terms of receiver coverage and total available habitat. Although this contributed a

bias within the analysis, it appeared from the movement relocation data that open bay habitat was

"used" primarily as transitional habitat or as a movement corridor, as opposed to the other habitat

types where relocations occurred more often and for longer periods of time. In addition, only

four habitat types (creek, mangrove, open bay, and pass) classified by SBNEP were considered

in this study. Other more fine scale habitat types such as oyster bars or seagrass may be

considered for future work.









in reservoirs (e.g., Jackson and Hightower 2001) and marine reserves (e.g., Meyer et al. 2000).

The suggestion that snook demonstrate high site fidelity to specific habitats in a bay system

poses a concern to either maintain or improve these habitats which ultimately provide

advantageous resources (e.g., food sources and/or refuge) during certain life history stages. In

particular, it appeared that snook exhibit high site fidelity toward specific creeks primarily during

winter seasons and specific pass habitats during summer seasons. This suggests the significance

of individual habitat types and locations as potentially important year-round habitats for feeding,

breeding, and refuge.

High site fidelity may also prove to be disadvantageous in certain instances. For example,

it appeared that the maj ority of snook harvested by anglers demonstrated high site fidelity to the

open bay habitat near VR2 1, located in the northern portion of the bay. A stationary strategy

such as this may be beneficial to conserving energy while foraging. These fish, however, may

ultimately be more susceptible to harvest by anglers. Fish that exhibited high site fidelity to

open bay areas and creeks had fewer days-at-large than fish that moved between habitat types.

Therefore, potential inferences could be made regarding increased chances of survival based on

site fidelity although data such as angler effort would also need to be examined to make more

concrete predications about survivorship.

Another possibly disadvantageous habitat use strategy was related to pass site fidelity

during the spawning season (summer 2005). The one fish that was found dead, presumably as a

result of the red tide bloom, most likely came to New Pass to spawn but was unable to survive

the extremely exaggerated red tide cell counts during that time. Natural mortality due to the red

tide bloom was also suspected, but not confirmed, for seven other fish. These latter fish were

last detected within northern bay passes in summer 2005. Snook that did not utilize passes in the









CHAPTER 5
CONCLUSIONS

This telemetry study provides insight into spatial and temporal patterns of habitat use and

may serve as a first step towards identifying essential Eish habitat (Arendt et. al 2001) for snook

in Sarasota Bay, Florida. In this study, the relocations of individual Eish were used as a metric to

identify key habitats used by common snook. This is particularly important in linking the use of

critical seasonal habitats, such as winter creek systems and summer spawning habitats, with

environmental and anthropogenic threats in Sarasota Bay. Both scenarios of physical and

environmental disturbances can lead to population level impacts within an aquatic ecosystem.

These impacts may include reduced growth of individuals, recruitment, and survival in an area

where a disturbance has occurred. It is therefore important to recognize behavioral choices and

potential bet-hedging strategies demonstrated by individuals, such as movement and habitat use,

as they may ultimately provide insight into factors contributing survival.

These new findings provide insight into individual behaviors of snook which may be

adaptive strategies that contribute to an individual's chance of survival by increasing or

decreasing susceptibility to possible sources of mortality (e.g., harvest, HABs, and displacement

from refuge habitats). For example, it appeared that there was a distinct seasonal movement and

habitat use pattern demonstrated by individual snook which may have increased the likelihood of

these fish surviving the large scale red tide bloom in Sarasota Bay. The fish that survived the

bloom transitioned from northern creek habitats to the southern extent of the bay at Venice Inlet

during the summer months whereas the fish that most likely died as a result of the red tide bloom

used passes in the northern bay.

The significance of this study is that it improves our understanding of spatial and temporal

relationships between an aquatic species and a variety of habitats. This study also documents









Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science

EXAMINING SEASONAL MOVEMENT AND HABITAT USE PATTERNS OF ADULT
COMMON SNOOK

By

Lauren Marcinkiewicz

December 2007

Chair: William E. Pine
Major: Fisheries and Aquatic Sciences

The common snook, Centropomus undecimalis, is an ecologically and economically

important estuarine dependent predatory fish species found throughout south Florida. Despite

increasingly restrictive management actions over the past 50 years, common snook populations

are thought to have declined. Possible reasons for this decline are high harvest rates and loss of

essential habitat related to coastal development. I evaluated habitat use and movement patterns

for adult snook in seasons with and without large-scale environmental (red tide blooms) and

anthropogenic (dredging) disturbance events. Results of my study support much of the literature

on snook life history while providing new behavioral information regarding movement, site

fidelity, and habitat disturbances. My study provides important information for conservation

management purposes and improves the understanding of direct and indirect effects of habitat

threats associated with anthropogenic and environmental disturbances on snook populations.

This understanding of habitat-species relationships is important because of the emphasis placed

on managing habitat by various State and Federal agencies for the conservation of Eish and

wildlife resources.









CHAPTER 1
INTTRODUCTION

Development and implementation of successful conservation and management strategies

for terrestrial and aquatic organisms relies on a sound understanding of their ecological

requirements. In recent years, increasing attention has been given to the habitat conservation

approach with the motivation that protecting habitat will ensure population viability. This

approach, in fact, is a maj or component of many State and Federal mandates, including the

Magnuson-Stevens Fishery Conservation and Management Act (MSFCMA) for essential fish

habitat (EFH), which requires using a habitat-oriented and ecosystem-based approach to develop

effective management and conservation plans.

Sufficient habitat is a necessary requirement for survival of wildlife and aquatic

populations (Morrison et al. 1992). Management of fisheries resources typically follows two

approaches: (1) regulating harvest to maintain sustainable populations and (2) preserving and

improving species' habitats through protective or restoration measures. In the United States, the

development of "ecosystem based management", where these two approaches are integrated into

a single management strategy, has become the mandate for fisheries management (NRC 2006).

For ecosystem based management to be successful, an adequate understanding of the

relationships between species and their habitat is necessary (Knapp and Owens 2005). This

requires a thorough understanding of the types of habitats required for a species to live at all life

stages, preferably through quantitative exploration of the species' resource use patterns (Oppel et

al. 2004). As resources may include anything that an animal may ultimately require, such as

foraging, refuge, and rearing habitats, monitoring patterns of interaction between species and

their habitat may ultimately provide insight into the dynamic factors that drive viable









Table 2-1. Total area (m2) and percent available for each habitat type in Sarasota Bay, Florida.
Habitat type Area m2 Percent available
Creek 4236249 2.95
Mangrove 9470858 6.58
Open Bay 127673723 88.78
Pass 2425627 1.69
Total 143806459 100.00

Table 2-2. VR2 habitat location with assigned numerical location, indicating geographical
position around Sarasota Bay, and associated VR2 habitat type.
VR2 site Numerical assignment Habitat type


Longboat Moorings (LBMM)
Longboat Pass
Cortez Pass
Tidy Island
Bayshore
Bowlees Creek (mouth)
Bowlees Creek (inside)
Haunted House
Johnny Pilings
Whitaker (mouth)
Whitaker (inside)
Fountain
Hudson Bayou
Siesta Islands
Phillippi ICW
Phillippi Creek
Coral Cove
North Creek Outer
North Creek Tunnel
North Creek Pilings
North Creek Upper
Spanish Point
South Creek (mouth)
South Creek (inside)
Pops Dock
Big Pass
Sunken Barge
Backdock
New Pass


1
2-4
5-7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30-32
33
34
35-36


Open bay
Pass
Pass
Mangrove
Mangrove
Creek
Creek
Open bay
Open bay
Creek
Creek
Open bay
Mangrove
Mangrove
Mangrove
Creek
Open Bay
Mangrove
Creek
Creek
Creek
Mangrove
Creek
Creek
Pass
Pass
Mangrove
Mangrove
Pass












TABLE OF CONTENTS


page

ACKNOWLEDGMENTS .............. ...............4.....


LIST OF TABLES .........__.. ..... .__. ...............6....


LIST OF FIGURES .............. ...............7.....


AB S TRAC T ......_ ................. ............_........8


CHAPTER


1 INTRODUCTION ................. ...............9.......... ......


2 MATERIALS AND METHODS .............. ...............14....


Study Site ................. .. .............. ... ...............14.....
Determining Movement and Habitat Occupancy .............. ...............14....
Defining and Monitoring Available Habitats ................. ......... ......... ...........1
A nalyses............... .. ... .......... .............1
Assessing Seasonal Movement and Habitat Use Patterns ................. ............ .........16
Site Fidelity ...................... .... .... ........ ........1
Impacts of Habitat Disturbance on Movement and Habitat Use ................. ................. 18
Relating Movement and Habitat Use Patterns with Survivorship ................. ................19

3 RE SULT S .............. ...............25....


Assessing Seasonal Movement and Habitat Use Patterns .............. ...............25....
Site Fidelity....................... ... .. ... ....... .......2
Impacts of Habitat Disturbance on Movement and Habitat Use ................. .....................27
Relating Movement and Habitat Use Patterns with Survivorship ................ ............... ....28

4 DI SCUS SSION ................. ...............40................


5 CONCLUSIONS .............. ...............47....


APPENDIX: ADDITIONAL TABLES AND FIGURES .............. ...............49....


LIST OF REFERENCES ................. ...............50................


BIOGRAPHICAL SKETCH .............. ...............53....









CHAPTER 4
DISCUSSION

Along with confirming results from several life history studies, including the association of

habitat use with specific habitat types (e.g., Gilmore et al. 1983 and Muller and Taylor 2006),

new insights have been gained regarding habitat site fidelity and variable movement patterns of

adult common snook. These new Eindings provide insight into individual behaviors of snook

which may be adaptive strategies that increase an individual's chance of survival by decreasing

susceptibility to possible sources of mortality (harvest, HABs, and displacement from refuge

habitats). For example, it appeared that there was a distinct seasonal movement and habitat use

pattern demonstrated by individual snook which may have increased the likelihood of these fish

surviving the large scale red tide bloom in Sarasota Bay, during summer 2005.

Survivors of the red tide bloom generally spent extended periods of time through the fall

and winter in the creek habitats found in northern Sarasota Bay. However, during summer 2005

many of these fish were found in the most southern areas of Sarasota Bay around Venice Inlet.

This may have increased the probability of these fish surviving the red tide bloom during

summer 2005 because southern Sarasota Bay appeared to have lower levels of fish kills (Bennett

2006), likely due to the higher exchange rate with the Gulf of Mexico, and increased availability

of freshwater over areas in the southern regions of Sarasota Bay from creeks. Some fish were

last detected at the Venice Inlet location during the summer 2005 and were not relocated until

several months later at this same location. These fish may have either exited the bay system into

the Gulf of Mexico or traversed out of the VR2 array detection range from the Venice area of

Sarasota Bay to other bay and creek systems located further to the south (Roberts Bay, Curry

Creek, Lemon Bay and Alligator Creek, for example). This would not be unlikely as this study

has shown a number of individual fish moving distances > 30 km. In addition, at least three fish









following winter, spring and summer seasons. Relocations during this time were from batch 1

Eish and batch 2 Eish (beginning in the summer season). Year 3 began in fall 2006 and included

the following winter season. Relocations during this time were primarily from batch 2 fish as the

battery life of the tags from the maj ority of batch 1 fish had expired.

Site Fidelity

Relocations of individual fish were examined to determine if site fidelity was evident

based on the original capture habitat and location compared to other similar and different habitat

types. Relocations were grouped by habitat type and characterized by fish-days per individual

fish. To determine site fidelity at the original capture location, I required that only fish released

within the detection range of a VR2 be considered in the analysis. I calculated percent fish-days

spent at the site of capture for each individual snook included in the analysis. I inferred high site

fidelity if the percent of fish-days was highest at the original capture habitat and location, for the

entire time a fish was monitored. I also assessed individual creek site fidelity for fish captured

specifically in Bowlees Creek (n=6 fish) and Whitaker Bayou (n=9 fish) and the single fish

captured in South Creek.

Impacts of Habitat Disturbance on Movement and Habitat Use

I estimated habitat use by summing the total number of fish-days in each habitat per season

to determine if there was a difference in habitat use, based on percent fish-days, that may be

related to the red tide bloom or the dredging treatments. For the red tide bloom, I examined

habitat use within passes between the summer of this event (2005) and the summer of the

following year (2006) when the duration of elevated red tide cell counts was shorter (Figure A-

1). Snook use pass habitats as spawning sites in the summer and are known to aggregate in these

areas for several weeks each year. Pass habitats also often have high red tide cell count levels

because of their proximity to the Gulf of Mexico. I expected percent habitat use in passes to










LIST OF REFERENCES


Arendt, M. D., J. A. Lucy, and T. A. Munroe. 2001. Seasonal occurrence and site-utilization
patterns of adult tautog, Tautoga onitis (Labridae), at manmade and natural structures in lower
Chesapeake Bay. Fishery Bulletin 99:519-527.

Bennett, J. P. 2006. Using acoustic telemetry to estimate natural and fishing mortality of
common snook in Sarasota Bay, Florida. Master's thesis. University of Florida, Gainesville.

Brennan, N.P., C.J. Walters and K.M. Leber. In Press. Manipulations of stocking magnitude:
addressing density-dependence in a juvenile cohort of common snook, Centropomus
undecimalis. Reviews in Fisheries Science.

Clements, S., D. Jepsen, M. Karnowski, and C.B. Schreck. 2005. Optimization on an acoustic
telemetry array for detecting transmitter implanted fish. North American Joumnal of Fisheries
Management 25:429-436.

Gilliam, J.F. and D.F. Fraser. 2001. Movement in corridors: enhancement by predation threat,
disturbance, and habitat structure. Ecology 82:258-273.

Gilmore, R. G., C. J. Donahoe and D.W. Cooke. 1983. Observations on the distribution and
biology of the common snook, Centropomus undecimalis (Bloch).
Florida Scientist 46:313-336.

Heithaus, M. R., L. M. Dill, G. J. Marshall, and B. Buhleier. 2002. Habitat use and foraging
behavior of tiger sharks (Galeocerdo cuvier) in a seagrass ecosystem. Marine Biology 140:237-
248.

Heupel, M.R., J.M. Semmens, and A.J. Hobday. 2006. Automated acoustic tracking of aquatic
animals: scale, design and deployment of listening station arrays. Marine and Freshwater
Research 57:1-13.

Howells, R. G., A. J. Sonski, P. L. Shafland, and B. D. Hilton. 1990. Lower temperature
tolerance of snook, Centropomus undecimalis. Short Papers and Notes. Northeast Gulf Sciences
11(2):155-158.

Jackson, J. A., and J. E. Hightower. 2001. Reservoir striped bass movements and site fidelity in
relation to seasonal patterns in habitat quality. North American Journal of Fisheries Management
21:34-45.

Jadot, C., A. Donnay, M. L. Acolas, Y. Cornet, and M. L. Begout Anras. 2006. Activity patterns,
home-range size, and habitat utilization of Salrpa salpa (Teleostei: Sparidae) in the
Mediterranean Sea. Journal of Marine Science 63:128-139.

Jorgensen, C., B. Emnande, O. Fiksen, and U. Dieckmann. 2006. The logic of skipped spawning
in fish. Canadian Journal of Fishies and Aquatic Science. 63:200-21 1.











Cortez


Lonighoat Pa~ss








































Legend




0 3 6


Bowlees Creek


New Pass




Big Pass


























12 Kilometers


Venice


Figure 2-1. Sarasota Bay, Florida highlighted with maj or tidal tributaries and passes.










LIST OF FIGURES


Figure page

2-1 Sarasota Bay, Florida highlighted with maj or tidal tributaries and passes. ........._...........22

2-2 The VEMCO@ VR2 numbers and locations in Sarasota Bay, Florida. Table 2-2
gives the VR2 numbers with corresponding name and associated habitat type. ...............23

2-3 This graph which shows relocations for an individual fish, 1936, depicts an example
of fish-days based on daily relocation dataOverlapping relocations in various habitat types,

2-4 Water temperature, following a dredging event which occurred in Whitaker Bayou in
late fall 2004, for two creek systems. ............. ...............24.....

3-1 Observed relocations of fish 1947 in Sarasota Bay, Florida. The solid arrow
indicates where the fish was originally captured, tagged, and released. The dashed
arrow indicates where the fish was last detected. ............. ...............34.....

3-2 Observed relocations of fish 1966 in Sarasota Bay, Florida. The solid arrow
indicates where the fish was originally captured, tagged, and released. The dashed
arrow indicates where the fish was last detected. ............. ...............35.....

3-3 Movement pattern based on relocations from VR2s for fish 1913. Refer to Table 2-2
for VR2 habitat location with assigned numerical location, indicating geographical
position around Sarasota Bay, and associated VR2 habitat type. .................. ...............36

3-4 Habitat use (percent fish-days) per season for Year 1 (2004/2005). ............. .................36

3-5 Habitat use (percent fish-days) per season for Year 2 (2005/2006). ............. .................37

3-6 Habitat use (percent fish-days) per season for Year 3 (2006/2007). ............. .................37

3-7 Average monthly water temperatures (oC) for an open bay area (New Pass) and a
creek habitat (Bowlees Creek) in Sarasota Bay, Florida. ............. .....................3

3-8 Habitat use (percent fish-days) at the original capture habitat and location for snook
(n=48). This graph is showing high site fidelity demonstrated by snook captured and
released at specific habitat types (creeks and open bay)............... ..................3

3-9 Seasonal habitat use (percent fish-days) in each of the tidal creeks before and after
the dredging event in Whitaker Bayou, Sarasota Bay, Florida ................. ................ ...39

A-1 2005 and 2006 red tide (K. brevis) cell counts for New Pass in Sarasota Bay, Florida. ...49


(1: creek, 2: 1









CHAPTER 3
RESULTS

Assessing Seasonal Movement and Habitat Use Patterns

In examining the movement patterns of all individually tagged snook between fall 2004

and winter 2007 I observed two general movement patterns: (1) "transient" fish that traveled

long distances to multiple habitats throughout the year, and (2) "resident" fish that moved

infrequently between habitats within a small geographic area. For example, Eish 1947 was

tagged and released in a mangrove habitat in the southern portion of the bay along the eastern

shoreline in fall 2004. This Hish was repeatedly relocated for over a year and a half in various

habitat types throughout the entire bay system including multiple creek, mangrove, and open bay

areas in both the northern and southern portion of Sarasota Bay (Figure 3-1). This Hish was last

detected at an open bay VR2 in summer 2006. In contrast, fish 1966 was tagged and released in

a creek habitat in the northeastern portion of the bay and was relocated primarily in its original

capture creek and nearby mangrove habitat for approximately seven and a half months until it

was last detected on a pass receiver. Thus, I assumed that the fish emigrated from the study

system (Figure 3-2).

Larger scale movement patterns tended to occur primarily during the late spring and

summer months for most fish. These travel patterns typically involved a fish transitioning from a

creek habitat in the northern portion of Sarasota Bay and moving to a southern pass habitat.

During the spring and early summer of 2005, 14 of 3 5 tagged fish demonstrated this type of

movement patterns as fish would move out of a creek habitat in the northern bay to nearby

habitats including other creeks, mangroves and open bay areas (e.g., fish 1913, Figure 3-3).

Distances traveled to the nearby habitats during this time, ranged between 0.6-3.0 km. The

transitional movement to nearby habitats typically lasted for one month. During late June and









was tagged in October 2004 approximately 650 m northeast of a VR2 adj acent to Siesta Key.

This fish was relocated in a mangrove habitat near this VR2 a month later during manual

tracking efforts. Following this relocation, the fish was detected on VR2s moving north until it

entered Whitaker Bayou. All subsequent relocations were within Whitaker Bayou prior to

harvest (February 2, 2005). The mean number of days-at-liberty for these seven fish was 128

days.

The final two fish that were harvested had a higher number of mean days-at-liberty (310

days) than the other seven fish. Both fish were tagged on the same date in early November 2004.

Fish 1932 was tagged in an open bay habitat in the northwest portion of the bay. While at

liberty, this fish exhibited considerable movement between its original capture location and

several pass habitats. It was last relocated in late August 2005 near the area in which it was first

captured. Fish 1962 was tagged in a mangrove habitat in the northeast portion of the bay. This

fish moved between its original capture location and a creek habitat (Bowlees Creek) throughout

the fall, winter, and early spring seasons. This fish was also relocated in various pass habitats

throughout the summer, and returned to Bowlees Creek and surrounding mangrove habitats in

the late summer. This fish was last relocated in late September 2005 within Bowlees Creek.

One fish, 1916, was assumed to have died as a result of the red tide bloom in summer

2005. This fish was originally tagged in an open bay habitat in the northwest portion of the bay

in November 2004. Relocations of this fish were infrequent within the first two months of when

it was first captured with one to two fish-days near a VR2 where it was originally captured.

Relocations remained infrequent during spring near a VR2 in mangrove habitat adj acent to Siesta

Key. In the summer, relocations were concentrated in New Pass. This fish was found dead on a










BIOGRAPHICAL SKETCH

Lauren Lee Marcinkiewicz was born in Miami, Florida. However, she grew up primarily

in Massachusetts. Lauren received her B.S. in marine biology from the University of California,

Santa Cruz, in 2001. After graduation, she returned to Massachusetts and worked as an observer

on commercial ground fishing boats. In 2004, Lauren moved to Sarasota, Florida, where she

worked as a technician under the supervision of Dr. William E. Pine, III at Mote Marine

Laboratory. In August 2004, Lauren joined Dr. Pine to begin her master' s research at the

University of Florida, Department of Fisheries and Aquatic Sciences. Lauren completed her

master' s research in 2007.









risk of predation, vulnerability to Hishing, or susceptibility to lethal conditions. Thus, it is critical

to understand the interactions between a species and its habitat for effective conservation and

management purposes.

In general, the best method to identify habitat use and movement by an animal is through

direct observation (White and Garrott 1990). When this is not feasible, which is often the case

with aquatic organisms, acoustic tracking techniques via telemetry can provide an adequate

substitute. Telemetry studies provide insight into spatial and temporal use of habitats and can be

a first step in identifying EFH (Arendt et al. 2001). In the case of Eishes, telemetry provides

spatial and temporal tracking of individual movement and habitat use patterns which may

ultimately reveal the most ecologically important habitats (Savitz et al. 1983). This method

provides insight about key behaviors such as foraging (Heithaus et al. 2002), activity patterns

(Jadot et al. 2006), seasonal movement and site fidelity (Jackson and Hightower 2001). It also

provides a means to estimate home ranges (Morrissey and Gruber 1993) and mortality rates

(Bennett 2006). Ultimately, combining seasonal movement and site fidelity information with

habitat-specific mortality estimates (both natural, M, and fishing, F) can facilitate predictions

regarding the effects of habitat alterations on survivorship.

Acoustic telemetry was used in this study to examine seasonal movement and habitat use

patterns of adult common snook, Centropomus undecimalis. Common snook are an ecologically

and recreationally important apex predator found throughout the tropical Caribbean basin

including south Florida. In Florida, snook are abundant along the Gulf of Mexico coast from

Tampa Bay south to the Florida Keys and north to Cape Canaveral along the Atlantic coast

(Muller and Taylor 2006). Throughout different life stages snook use a range of habitats from

offshore reefs to inland lakes and are generally considered diadromous (Rivas 1986). As snook










LIST OF TABLES


Table page

2-1 Total area (m2) and percent available for each habitat type in Sarasota Bay, Florida. .....20

2-2 VR2 habitat location with assigned numerical location, indicating geographical
position around Sarasota Bay, and associated VR2 habitat type. .................. ...............20

2-3 Area (m2) and percent area monitored by VR2s for each habitat type in Sarasota Bay,
Florida. .............. ...............21....

3-1 Chi-square test (a=0.05) results to determine if there was a significant difference
between ob served and expected habitat use based on percent fi sh-days ................... ........3 1

3-2 Original capture habitat and location data for snook released within the detection
range of a VR2. ............. ...............3 2....

A-1 Months included in each season, characterized by average monthly water
temperature (oC) for Sarasota Bay, Florida. ............. ...............49.....

















pass
pass
mangrove
pass
mangrove
pass
mangrove
mangrove
pass
mangrove
mangrove
mangrove
creek
open bay
open bay
open bay
creek
open bay
open bay
mangrove
open bay
creek
open bay
creek
pass
creek
open bay
creek
open bay
mangrove
creek
creek
creek
creek
open bay
mangrove
creek
mangrove
open bay


section

Percent fish-


Table 3-2. Original capture habitat and location data for snook released within the deter
range of a VR2.
Fish ID Capture Size (TL) Capture Capture habitat
date mm location
(VR2)


days at
capture habitat
and location
3.0
34.0
0.0
23.0
57.0
5.0
27.0
3.0
43.0
4.0
12.0
86.0
53.0
81.6
97.8
99.5
54.0
28.0
60.0
5.6
33.3
20.0
87.9
39.0
81.0
97.0
93.6
81.0
63.8
37.0
92.0
69.0
71.0
26.0
100.0
85.0
79.0
6.6
13.0


1646
1647
1648
1649
1650
1654
1656
1662
1663
1666
1906
1912
1913
1916
1917
1918
1920
1922
1923
1924
1926
1931
1932
1935
1936
1938
1941
1943
1945
1949
1950
1951
1955
1956
1957
1958
1959
1961
1962


8/18/2006
8/18/2006
6/23/2006
8/18/2006
6/23/2006
8/18/2006
6/23/2006
6/23/2006
8/18/2006
6/23/2006
10/12/2004
10/26/2004
12/2/2004
11/3/2004
11/3/2004
11/3/2004
10/20/2004
11/3/2004
11/3/2004
10/28/2004
11/3/2004
10/20/2004
11/3/2004
12/2/2004
10/21/2004
10/20/2004
11/3/2004
12/2/2004
11/3/2004
10/28/2004
10/20/2004
12/2/2004
12/2/2004
12/2/2004
11/3/2004
10/26/2004
12/2/2004
11/2/2004
11/3/2004


734
694
856
739
917
817
910
662
710
644
721
663
856
689
714
707
932
750
683
1100
705
853
720
819
668
816
748
700
683
712
850
722
845
670
687
681
761
776
856









exhibited the previously described pattern (northern creeks to southern passes in the summer) for

two consecutive years. This suggests a potentially beneficial behavioral strategy for these

individual fish making them less susceptible to mortality associated with maj or red tide blooms

in pass habitats in the summer spawning months. Overall, fish that were identified as natural

mortalities from the red tide bloom in Bennett (2006) were most frequently relocated on pass

receivers in the northern bay. During the summer 2005 red tide bloom, it appeared that fish kills

were greatest in the northern portion of Sarasota Bay.

Fish that were detected in pass habitat in Year 1 (red tide bloom) that survived to the

following summer were part of the group of fish that showed increased utilization of creek and

mangrove habitats in the summer of Year 2. This decline in pass habitat use may be related to a

decrease in the number of fish that were available to be monitored in the system, but it could also

indicate that individual fish may not return to spawning areas with the same frequency each year.

Jorgensen (2006) showed that Atlantic cod Gadus morhua are annual spawners when young.

However, as the fish mature they exhibit skip-year spawning. Older fish, in fact, spawn only

every second or third year. Female Gulf sturgeon, Acipenser oxyrhincys desotoi, may also skip

spawn as they are thought to spawn on 3-4 year intervals (Pine et al. 2001).

A multi-year spawning interval such as this could be advantageous for common snook for

several reasons. First, spawning is energetically very costly, particularly for females (Jorgensen

2006) and the energetic demands of producing the large gametes of adult snook are likely high.

Second, pass habitats are likely the "most risky" habitats that adult snook occupy. Pass habitats

of Sarasota Bay are generally the first to be exposed to red tide blooms originating from the Gulf

of Mexico. Additionally, pass habitats are more likely than other habitats in the bay to support

potential predators of adult snook including a variety of shark species (C. Simpfendorfer, Mote









were tagged with 180-day tags. The group of fish (n=3 1) tagged in the summer 2006 was

referred to as "batch 2". All snook were tagged and released at the original site of capture.

Tagged snook were relocated using an array of underwater, autonomous VEMCO@ VR2

receivers (Vemco Ltd., Shad Cay, Nova Scotia, Canada). Acoustic receivers were programmed

to record the unique tag code, date, and time when a tagged snook was within the monitoring

range of the VR2. Listening stations were positioned strategically throughout Sarasota Bay

including the northern and southern extreme portions of the bay, passes, and maj or tidal

tributaries (Figure 2-2). Data from the VR2s was retrieved on an 8 to 12 week schedule between

October 2004 and March 2007. At least 29 receivers were constantly deployed in Sarasota Bay

during the study period as part of this and other cooperative proj ects with Mote Marine

Laboratory, Sarasota, Florida.

Snook were also relocated manually using a Vemco@ VR100 receiver and directional

hydrophone. These active searches were designed to "sweep" major areas of Sarasota Bay not

covered by the VR2 array. Two tracking methods were used: (1) a "hopscotch" method in which

tracking was conducted along the entire shoreline of the bay at 300 m intervals and (2) a search

method in which random GPS points were selected to monitor all areas of the bay. Manual

tracking efforts were conducted opportunistically from fall 2004 to winter 2006 with the largest

amount of effort occurring during summer 2005.

Defining and Monitoring Available Habitats

An existing classification of available habitat types in Sarasota Bay, developed for the

Sarasota Bay National Estuary Program (SBNEP) (Serviss and Sauers 2003) was used to define

four distinct habitat types: creek, mangrove, open bay, and pass (Table 2-1). Habitat types for

individual VR2 monitoring stations were assigned by overlaying VR2 GPS coordinates onto pre-

existing GIS data layers. Each VR2 was given a numerical assignment based on its location, a





























































O 2 4 8 IMorneters
1 I 1 1 1 1

Figure 3-1. Observed relocations of fish 1947 in Sarasota Bay, Florida. The solid arrow
indicates where the fish was originally captured, tagged, and released. The dashed
arrow indicates where the fish was last detected.


Gulf of Mexico



















Legend
a re location of fish #1947 at a VR2









39% in winter Year 2. After dredging began, habitat use decreased within Whitaker Bayou and

increased among other creek systems, most notably in Phillippi Creek. This, however, may be

an affect of a decrease in batch 1 Eish (due to mortality and emigration), that had site fidelity

towards Whitaker Bayou, still alive and monitored in 2006. Additionally, most of the 25 Eish

tagged in summer 2006 were initially captured in mangrove and pass habitat approximately 4km

or less from the mouth of Phillippi Creek. Nevertheless, four of the nine fish relocated in

Whitaker Bayou in winter Year 1 were relocated the following winter in other habitats. Three of

these fish were relocated in other creek systems (Bowlees Creek or Phillippi Creek). The fourth

fish was relocated primarily in a mangrove habitat near Siesta Key Island. Therefore, it appeared

that some individual snook demonstrated adaptive strategies in response to displacement by

moving to other creek or habitat areas.

These are important findings because Whitaker Bayou is a rearing habitat for juvenile

snook and a known wintering location for snook of all sizes (Brennan et al., in press). The loss

of this flocculent bottom material likely led to the cooler winter temperatures in Whitaker Bayou

which potentially eliminated this creek habitat as a winter refuge. The decrease in water

temperature in Whitaker Bayou compared to Bowlees Creek post-dredging (Figure 2-4) is

suggested as a factor leading snook to seek thermal refuge in other creek systems. The

possibility of impacts at the individual level, which affect populations, such as reduced growth,

recruitment, and survival due to habitat degradation and/or loss, should be considered when

making management decisions regarding habitat and species protection.

Issues regarding habitat protection, as well as fisheries management, are often closely

linked to individual habitat site fidelity. Evidence of site fidelity has been widely documented in

relation to the importance in developing management strategies of spatially explicit populations









descriptive name and an associated habitat type (Table 2-2). The percent area of each habitat

type monitored was calculated as:

aeVR2habita" -* 100 (2-1)
total area monitored

where areaVRzhabitatX is the area of a monitored habitat type X with VR2 receiver coverage and

total area monitored is the sum of the area of all habitats monitored within theVR2 array (Table

2-3). The variable areaVRzhabitatX WaS calculated as:

N F *r 2 (2-2)

where N is the number of receivers in the specific habitat, and r was the radius of the VR2

detection range (150 m) as determined from a series of range tests (Bennett 2006).

Analyses

Assessing Seasonal Movement and Habitat Use Patterns

I summarized seasonal movement for individually tagged snook using relocation data from

the VR2 array. Relocation data was infrequent from the manual tracking efforts, therefore, I did

not include it in the analyses. I plotted individual movement patterns within the bay system to

determine if snook exhibit distinct seasonal movements. I used individual movement patterns to

describe generalized patterns exhibited by the population. I also used the relocation data to

compare seasonal habitat use patterns for the population of tagged snook in Sarasota Bay with

previously documented snook life history information. Habitat use was characterized by "fish-

days". A fish-day was defined as an individual date that a fish was recorded by a VR2 in a given

habitat location (creek, mangrove, open bay, or pass). Consequently, as it was possible for a fish

to occupy the four different habitat types in one day, an individual fish could have potentially

contributed up to four fish-days per 24 hour time period. Figure 2-3 depicts an example of fish-

days, based on daily relocations, for an individual fish over a three month time period. An









Marine Laboratory, personal communication) and dolphins (R. Wells, Mote Marine Laboratory,

personal communication). Thus, it seems reasonable that adult snook would minimize their time

in the risky habitats. Although further research is required to confirm this, skip-spawning may

be a potentially advantageous evolutionary trait exhibited by some snook in Sarasota Bay,

especially during periods when environmental conditions are unfavorable.

Unfavorable habitat conditions that are a result of anthropogenic disturbances, such as

dredging, may lead to displacement. This displacement could potentially have negative

population level impacts by increasing an individual's susceptibility to sources of mortality

including exposure to predators (Walters and Juanes 1993) or lethal environmental conditions.

Cederholm and Reid (1987) summarized the impacts of forest management via logging on

Northwest coho salmon Oncorhynchus kisutch populations. They describe decreases in

resilience mechanisms (e.g. excess spawning and abundant fry) and survival over a variety of life

stages which resulted from an increase in suspended sediments and a decrease in refuge habitats.

A decrease in resiliency and survival from anthropogenic habitat degradation such as this,

combined with overfishing, resulted in an overall decrease in coho salmon stocks. This result led

Cederholm and Reid (1987) to suggest an integrated approach to natural resource management

which includes the protection of habitats used by fish through the combined efforts of the fishery

and forestry industries.

During this proj ect, Whitaker Bayou was subj ect to a maj or physical modification when a

channel was dug to increase boat access to a new marina complex. This dredging project

removed a layer of flocculent organic material that helped to keep Whitaker Bayou warm during

winter months due to decomposition and solar warming. Before dredging began, the percent of

habitat use in Whitaker Bayou was relatively high, ranging between 44%, in fall Year 2, and










Klimley, A.P., F. Voegeli, S.C. Beavers, and B.J. Le Boeuf. 1998. Automated listening stations
for tagged marine fishes. Marine Technology Society Joumnal 32:94-101.

Knapp, C. R., and A. K. Owens. 2005. Home range and habitat associations of a Bahamian
iguana: implications for conservation. Animal Conservation 8:269-278

Marshall, A. R. 1958. A survey of the snook fishery of Florida, with studies of the biology of the
principal species, Centropomus undecimalis (Bloch). Florida Board of Conservation Marine
Research Laboratory Technical Series Number 22.

Meyer, C. G., K. N. Holland, B. M. Wetherbee, and C. G. Lowe. 2000. Movement patterns,
habitat utilization, home range size and site fidelity of whitesaddle goatfish, Parpeneus~~~~PPPP~~~~PPPP
porphyrus, in a marine reserve. Environmental Biology of Fishes 59:235-242.

Morrison, M. L., B. G. Marcot, and R. W. Mannan. 1992. Wildlife-habitat relationships:
concepts and applications. University of Wisconsin Press, Madison.

Morrissey, J. F., and S. H. Gruber. 1993. Home range of juvenile lemon sharks, Negaprion
brevirostris. Copia 2:425-434.

Muller, R. G. and R. G. Taylor. 2006. The 2005 stock assessment update of common snook,
Centropomus undecimalis. Fish and Wildlife Conservation Commission, Florida Marine
Research Institute, St. Petersburg.

Oppel, S., H. M. Schaefer, V. Schmidt, and B. Schroider. 2004. Habitat selection by the pale-
headed brush-Hinch (Atlapetes pallidiceps) in southern Ecuador: implications for conservation.
Biological Conservation 118:33-40.

Pine, W. E., III, M. S. Allen, and V. J. Dreitz. 2001. Population viability of the Gulf of Mexico
sturgeon: Inferences from capture-recapture and age-structured models. Transactions of the
American Fisheries Society 130:1164-1174.

Pine, W. E., III, L. L. Marcinkiewicz, and J. P. Bennett. 2007. Examining adult snook habitat
occupancy, movement and exploitation rate patterns in Sarasota Bay, Florida. Florida Fish and
Wildlife Conservation Commission, St. Petersburg.

Rivas, L. R. 1986. Systematic review of the perciform fishes of the genus Centropomus. Copeia
1986:579-611.

SAS Institute. 1996. SAS users guide: statistics, version 6. 4th edition. SAS Institute, Cary, North
Carolina.

Savitz, J., P. A. Fish, and R. Weszely. 1983. Habitat utilization and movement of Eish as
determined by radio-telemetry. Journal of Freshwater Ecology 2: 165-174.









CHAPTER 2
MATERIALS AND METHODS

Study Site

Sarasota Bay (Figure 2-1) is a moderately sized, subtropical estuary located along the

southwest Florida coast. Sarasota Bay was identified as an Estuary of National Significance in

1987 by the United States Congress and has since been included in the National Estuary

Program. Sarasota Bay is approximately 44 km in the north-south direction and includes an area

of about 1 14 km2. Sarasota Bay and its associated tidal tributaries, sub-bays, and canals are

separated from the Gulf of Mexico by a series of narrow barrier islands, including Casey Key,

Siesta Key, and Longboat Key, and connect with the Gulf through a series of narrow passes.

All sampling for this study was conducted between Cortez Bridge (Cortez, Florida) and

Albee Bridge (Venice, Florida) at the southernmost extent of the bay, just north of Venice Inlet

(Figure 2-1). Within Sarasota Bay proper, there are three passes connecting Sarasota Bay and

the Gulf of Mexico (Longboat Pass, New Pass, and Big Pass), as well as five maj or tidal

tributaries (Bowlees Creek, Whitaker Bayou, Phillippi Creek, North Creek, and South Creek,

Figure 2-1). This study focused only on the waters of Sarasota Bay and did not include

nearshore areas of the Gulf of Mexico.

Determining Movement and Habitat Occupancy

During fall 2004, 75 adult common snook were surgically implanted with a uniquely

coded, long-life (700-day), Vemco@ acoustic telemetry tag (Vemco Ltd., Shad Cay, Nova

Scotia, Canada). Three angler returned tags were later reused and implanted in newly caught

snook (April 2005). These fish were referred to as "batch 1". In summer 2006, five angler

returned tags and one tag retrieved from a fish believed to have died of natural causes (red tide

bloom), were reused to tag other adult snook. During this time, an additional 25 adult snook



































Gulf of Mexico



















Legend
a re location of fish #19BB at a VR2


O 2 4 8 IMorneters
1 I 1 1 1 1

Figure 3-2. Observed relocations of fish 1966 in Sarasota Bay, Florida. The solid arrow
indicates where the fish was originally captured, tagged, and released. The dashed
arrow indicates where the fish was last detected.










Table 3-2. Continued
Fish ID Capture
date


1963 11/3/2004
1965 11/22/2004
1966 10/20/2004
1967 10/21/2004
1969 10/7/2004
1971 12/2/2004
1973 12/2/2004
1975 12/3/2004
51937 4/15/2005


Size (TL) Capture
mm location
(VR2)


Capture habitat


Percent fish-
days at
capture habitat
and location
100.0
95.0
23.0
82.0
94.0
1.0
46.0
89.0
0.0


666
855
896
596
596
615
851
655


open bay
creek
creek
pass
creek
creek
creek
mangrove
open bay











Table 3-1. Chi-square test (a=0.05) results to determine if there was a significant difference
between observed and expected habitat use based on percent fish-days.
Year Season X2 value d.f. p-value
1 fall 423.4 3 < 0.0001
winter 2857.5 3 < 0.0001
spring 395.7 3 < 0.0001
summer 8.9 3 0.0300
2 fall 41 5.9 3 < 0.0001
winter 1075.9 3 < 0.0001
spring 146.8 3 < 0.0001
summer 450.3 3 < 0.0001
3 fall 140.4 3 < 0.0001
winter 106.7 3 < 0.0001














Table A-1. Months included in each season, characterized by average monthly water
temperature (OC) for Sarasota Bay, Florida.
Season Months Average water
temperature (oC)


APPENDIX
ADDITIONAL TABLES AND FIGURES


Fall


October, November

December, January
February, March
April, May

June, July
August, September


24.6

18.1

24.1

29.6


Winter

Spring

Summer


6,000,000



4,000,000


- Observed fish mortality


2,000,000


~ cEf ~ 5
,bb b bat
bulVI~
C/IC/IC/I
Date


bbb
ulul
ul


Figure A-1. 2005 and 2006 red tide (K. brevis) cell counts for New Pass in Sarasota Bay,
Florida.










populations. These patterns are directly related to individual behavioral choices regarding

movement and habitat interactions.

In developing effective management strategies for a fishery, it is important to identify the

linkages between individual fish behavior and habitat resources in order to understand the

implications of anthropogenic and environmental disturbances on populations. Physical

disturbances related to coastal development, such as dredging and shoreline modification, are

readily visible and obvious examples of habitat modification. However, less consideration is

given to environmental disturbances such as harmful algal blooms (HABs e.g.; "red tide

blooms"). HABs have been linked to widespread fish and marine mammal mortality events and

are thought to be increasing in frequency and duration across much of southwest Florida

(Mahadevan et al. 2005).

HABs represent a unique case of habitat loss as they do not necessarily result in the loss of

structural habitat. However, HABs may make otherwise suitable habitat unusable (or even

lethal) for extended periods of time. Red tide blooms, because of their toxic nature, are likely to

force fish and other species to occupy sub-optimal habitats or elicit emigration from the system

to areas not affected by the HAB event.

Physical habitat alterations that result from dredging and development and other

environmental disturbances such as HABs can have large impacts on fish populations.

Reductions in growth, for example, can lead to lower fecundity and even survival rates which, in

turn, can have marked population-level consequences. To understand the mechanisms that cause

these population-level impacts, it is important to recognize behavioral choices and potential bet-

hedging strategies demonstrated by individuals. Individual choices related to survival may

include variable movement patterns or the use of alternative habitats to reduce an individual's










early July these fish traveled to the southernmost portion of the bay where they were detected on

a VR2 that was located in the Intracoastal Waterway (ICW) just north of the entrance to Venice

Inlet for varying time intervals. In most cases these fish would return to the same northern bay

habitats where they were located earlier in the year. For a few fish (n=3), this pattern was

demonstrated on an annual basis over a two-year time period. Straight-line, one-way distances

for all tagged snook, between recorded relocations, ranged from zero (fish that were only

detected at one receiver location) to >30 km.

All four monitored habitat types classified by SBNEP were used by adult snook throughout

this study, although patterns of habitat use varied among seasons and years (Figures 3-4, 5, and

6). Results from chi-square analyses (a = 0.05) indicated a significant dependence between

habitat and season for Year 1 (X2 = 2024.69, df = 9, p = < 0.0001), Year 2 (X2 = 334.43, df = 9, p

= < 0.0001), and Year 3 (X2 = 55.12, df = 3, p = <0.0001). Hence, there was a general

association of snook habitat use patterns with both habitat type and season. There was also a

significant difference in the X2 analysis (a = 0.05) between expected and observed habitat

occupancy for each season in years 1, 2, and 3 (Table 3-1).

Throughout fall and winter, when water temperatures in creek habitats were typically

warmer than open water areas (Figure 3-7) habitat use, determined by fish-days from relocation

data, for the tagged snook was highest in creeks. Over fifty-percent of all fall and winter

observations during years 1 and 2 were in creek habitats. In spring, Year 1, habitat use was

highest in mangroves and accounted for 39% of all observations. In spring, Year 2, habitat use

was highest in creeks and accounted for 52% of all observations. Habitat use differed between

the summers in years 1 and 2. In summer, Year 1, use was greatest in passes (34%). In summer,

Year 2, mangrove habitat was used most often, accounting for 51% of all observations. Fall and











31
29
27
S25
S23




S7-
' 5-
S3-
S11








S70


S60
IE 50
a 40
30
S20
PI 10
-


Fall Winter Spring Summer

Seasons (2004/2005)

0 Creek a Mangrove 0 Open bay 0 Pass

Figure 3-4. Habitat use (percent fish-days) per season for Year 1 (2004/2005).


~










Serviss, G. M., and S. Sauers. 2003. Sarasota Bay juvenile fisheries habitat assessment. Sarasota
Bay National Estuary Program, Sarasota.

Walters, C.J. and F. Juanes. 1993. Recruitment limitation as a consequence of natural selection
for use of restricted feeding habitats and predation risk taken by juvenile fishes. Canadian
Journal of Fisheries and Aquatic Sciences 50:2058-2070.

White, G. C., and R. A. Garrott. 1990. Analysis of wildlife radio-tracking data. Academic Press.
San Diego, California.

Zar, J. H. 1999. Biostatistical analysis, fourth edition. Prentice Hall. Upper Saddle River, New
Jersey.









ACKNOWLEDGMENTS

I would like to thank my graduate advisor, Bill Pine, for which none of this would have

been possible, along with the rest of my graduate committee; Tom Frazer and Ken Leber. I

would also like to thank everyone from the following organizations:

University of Florida, Department of Fisheries and Aquatic Sciencesl Jason "Mo"

Bennett, Darren Pecora, Matt Lauretta, Towns Burgess, Jake Tetzlaff, Jared Flowers, Elissa

Buttermore, Ed Camp

Florida Fish and Wildlife Conservation Commission: Behzad Mahoudi, Ron Taylor

Mote Marine Laboratory: Nate Brennan, Meaghan Darcy, Dave Wilson

I would also like to thank Captain John Dixon for his amazing snook netting skills, and Ed

Schmidt for his enthusiasm and countless hours of data crunching.





































O 2007 Lauren Lee Marcinkiewicz









example where this particular fish, 1936, contributed two fish-days to the analyses, were on

December 25, 2004 and March 15, 2005, where this fish was relocated in two different habitat

types (mangrove and pass) on the same day. Two or more relocations, or "hits" at a VR2 were

required to count as a fish-day to eliminate spurious detections that are sometimes recorded by a

VR2 from electronic equipment, marine mammals, or other noise sources (Clements et al. 2005;

Heupel et al. 2006; Klimley et al. 1998).

A series ofX 2 analyses were conducted to determine: (1) if there was a seasonal effect on

habitat type use, i.e. were habitat use and season independent, and (2) if there was a difference

between observed and expected habitat use for each season and year. Expected habitat use was

defined as:


areharriman N (2-3)
total area monitored Pshdy"wy

where Nfish-days WaS the total number of observed fish-days in a season. Observed habitat use was

the sum of the total number of fish-days recorded for each habitat per season.

The X 2 test statistic was calculated as:






where /f is the frequency, or number of counts, observed in class i (habitat type), and /3 is the

frequency expected in class if the null hypothesis is true (Zar 1999). All X2 tests were

conducted using the Statistical Analysis System (SAS Institute 1996) and Microsoft Excel.

Seasons were defined by average monthly water temperatures (Table A-1). Year 1 began

in fall 2004 and included the winter, spring and summer seasons that followed. Relocations

during this time were from batch 1 fish only. Year 2 began in fall 2005 and included the









northern portion of the bay during summer 2005 to spawn had perhaps increased their chances of

survival by escaping areas of the bay with the most concentrated red tide cell counts. This

demonstrates how site fidelity, as in the case of spawning location, could have large-scale

population impacts, i.e., genetic diversity of the population could be lowered over time if fish

that spawn in the northern passes are more susceptible to mortality events while fish who spawn

in southern pass are less impacted.

Overall, I found that snook use a variety of habitat types and spatial locations, and exhibit

a range of seasonal movement patterns. This diversity in behavior reduces the likelihood of any

one cataclysmic event, such as a massive red tide bloom, killing all adult snook in Sarasota Bay.

However, at least one tagged fish (1965) tagged in fall 2004 remained in the original creek where

it was captured throughout the two year time period this fish was monitored. That creek habitat

(South Creek) is located in the southern portion of Sarasota Bay. Occasionally this fish was

relocated on the pass VR2 near Venice Inlet during the summer seasons, but generally this fish

appeared to move very little from the creek where it was originally captured. This type of

behavior may have ultimately contributed to the survival of this fish by decreasing its exposure

to both fishing and natural (red tide) mortality. Similar variation in individual fish behavior has

been noted in other systems (Gilliam and Fraser 2001).

Adult snook used habitats in varying proportion compared to available habitat. This,

however, was based on the analysis that the available habitat, as well as the expected habitat use,

was equal to the proportion of each habitat type monitored by the VR2 array. VR2s were not

randomly placed throughout the bay as this study was originally designed to estimate snook

mortality rates and therefore necessary to relocate fish (see Bennett 2006). For example, open

bay, which makes up the maj ority of all available habitats in Sarasota Bay, had the smallest









In the summer of Year 2, mangrove habitat was used most often, accounting for 51% of all

observed fish-days.

Percent habitat use, based on fish-days within creeks, decreased in Whitaker Bayou

following the start of the large dredging event at the end of fall Year 2 (Figure 3-9). Percent

habitat use in Whitaker Bayou decreased from 44% in fall and 39% in winter of Year 2 to 13%

in fall and 0% in winter of Year 3. Simultaneously, percent habitat use in other creeks increased

over the seasons following the dredging event. This was most dramatically observed within

Phillippi Creek where percent habitat use increased from 13% in fall Year 2 to 53% in the fall

Year 3. This pattern was also observed between the winter seasons where percent habitat use

increased from 16% to 76%, between years 2 and 3, respectively.

Relating Movement and Habitat Use Patterns with Survivorship

Nine fish were harvested by anglers during this study. The number of days-at-liberty from

the original capture date to harvest ranged from approximately 100 to 340 days. All fish were

originally captured, tagged, and released in the northern portion of Sarasota Bay. Relocations

from these fish were also all in the northern portion of the bay. Appreciable movement was not

observed for four of the harvested fish as they were relocated nearly 100% of the time at one

open bay VR2 location (Longboat Marina and Moorings, VR2 1). Three of these fish were

originally tagged near this VR2 (1907, 1917, and 1963). The other fish, 1937, was tagged

approximately 2 km north of this location. Two fish, (1902 and 1909) were tagged in mangrove

habitat near VR2 33 between Lido Key and Big Pass. Fish 1909 was relocated 100% of the time

at VR2 33. Fish 1902 utilized Big Pass until January 26, 2005. This fish was not detected again

until March 6, 2005 in Big Pass which suggests that it may have moved into the Gulf of Mexico

during that time. Following this, habitat use was among mangroves near VR2 33 and Big Pass.

The last detection of this fish before it was harvested in April 2005 was at VR2 33. Fish 1930
















O Bowlees Creek a North Creek [ Phillipi Creek a SourthCreek a Whitaker

80-

70 -Dredging
I begins
60 in Whitaker
Bayou
S50

40 -0

S30-







Fall1 Winter 1 Spring 1 Sununer 1 Fall2 Winter 2 Spring 2 Sununer 2 Fall 3 Winter 3
Season

Figure 3-9. Seasonal habitat use (percent fish-days) in each of the tidal creeks before and after
the dredging event in Whitaker Bayou, Sarasota Bay, Florida.









winter of Year 3 were the last two seasons included in this study and during this time period

habitat use was highest in creek and mangrove habitats (fall: 38% creeks, 36% mangroves,

winter: 37% creeks, 36% mangroves). Snook habitat use in open bay varied within a range of 0-

21% among seasons and between years.

Site Fidelity

A table was constructed which included the date of capture, size, capture location (VR2),

capture habitat, and the percentage of fish-days at the original capture location for the 48 fish

captured, tagged and released within the detection range of a VR2 (Table 3-2). Data from this

table was used to graph habitat use, based on percent fish-days, to examine site fidelity for a

specific habitat and location (Figure 3-8). Overall, when all tagged fish released within the

vicinity of a VR2 were included in the analysis, I found that site fidelity was highest among fish

captured in creeks (63%) and open bay (69%) habitats.

There were a total of sixteen fish captured and released in three of the five creek habitats.

Six of these fish were from Bowlees Creek. The mean proportion of relocated fish-days for

these fish was 0.63 (SE & 0.15). Nine fish were released in Whitaker Bayou. Habitat use based

on the mean proportion of fish-days within Whitaker was 0.53 (SE & 0.08). One fish was

captured and released in South Creek. The proportion of relocated fish-days within South Creek

was 0.95. Although definitive conclusions are limited to the small numbers of fish captured

within specific creeks, this data suggests that snook may demonstrate high year round site

fidelity to the specific creeks in which they were first captured.

Impacts of Habitat Disturbance on Movement and Habitat Use

I observed a large decrease in percent habitat use, based on fish-days, for snook in pass

habitat between summer Year 1 (34%) and summer Year 2 (9%). During the summer, use of

creek and mangrove habitats by snook was higher in Year 2 than in Year 1 (Figures 3-4 and 3-5).









Concurrent with this study and the red tide bloom it was found that annual natural mortality rates

were much greater than the natural mortality rates currently used in the snook stock assessment

(Pine et al. 2007). Similarly, the dredging proj ect provided an experimental opportunity to

examine snook movement and habitat use patterns in relation to physical habitat alteration.

From previous quantitative sampling, Whitaker Bayou is thought to be a prominent nursery

habitat and wintering area for both juvenile and adult snook (Brennan et al., in press). A layer of

flocculent organic material in this system provides warmth during winter months due to

decomposition and solar warming. Both "experiments" provided the opportunity to examine the

impacts of environmental and anthropogenic disturbance events on habitat use and movement

patterns of adult snook, which may have affected an individual's likelihood of survival.









EXAMINING SEASONAL MOVEMENT AND HABITAT USE PATTERNS OF ADULT
COMMON SNOOK























By

LAUREN LEE MARCINKIEWICZ


A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE

UNIVERSITY OF FLORIDA

2007

















Fall Winter Spring
Seasons (2005/2006)


Summer


E Creek a Mangrove 0~ Open bay B Pass
Figure 3-5. Habitat use (percent fish-days) per season for Year 2 (2005/2006).


Winter


Seasons (2006/2007)
0B Creek Magrove 03 Open bay 0 Pass
Figure 3-6. Habitat use (percent fish-days) per season for Year 3 (2006/2007).


I, C,


70
S60
c 50
S40
S30
S20
10 -o
0-












_________ _____m__________


+ Relocations


12/04/04 12/19/04 01/03/05 01/18/05 02/02/05 02/17/05 03/04/05 03/19/05 04/03/05

Date

Figure 2-3. This graph which shows relocations for an individual fish, 1936, depicts an example
offish-days based on daily relocation data. Overlapping relocations in various
habitat types, (1: creek, 2: mangrove, 3: open bay, 4: pass) on a specific date,
constitute multiple fish-days contributed by an individual fish.







30.0

28.0 Bowless Creek + Whitaker Bayou

26.0



S22.0

S20.0

S18.0

16.0

14.0

12.0

10.0



Figuret 2-4 Wae tmeauefolwnadrgigvntwhihocre nWiae ao
in lat fal 204 fow reksses









increase in summer 2006 relative to 2005 because the duration of red tide cell counts exceeding a

level that is considered lethal to fish (200,000 cells/liter) was higher in 2005 than in 2006. I

expected snook to avoid passes during the high red tide events.

To assess the impact of dredging, I examined if the dredging event which occurred in

Whitaker Bayou led to differences in percent habitat use before and after the event between the

five tidal creeks. Snook are a cold water sensitive species (Marshall 1958) and Whitaker Bayou

is a prominent wintering area for snook (Brennan et al., in press). Therefore, I expected habitat

use to increase in other creek systems and decrease in Whitaker Bayou, particularly due to the

lower water temperatures within Whitaker Bayou compared to other creek systems, after

dredging began (Figure 2-4).

Relating Movement and Habitat Use Patterns with Survivorship

I examined habitat use and movement patterns of fish with known mortality fates (fishing

or natural). This included nine fish that were caught and had tags returned by anglers, and one

fish believed to have died as a result of the red tide bloom in summer 2005. I calculated the

mean "days-at-liberty" for the fish harvested by anglers and compared patterns among fish with

fewer days-at-liberty (<150 days) to those with a mean days-at-liberty > 150 days. Days-at-

liberty was defined as the number of days a fish was known to be alive post-capture, tagging, and

release.









findings on movement and habitat use in relation to anthropogenic and environmental sources of

habitat loss. Implications of habitat loss can include displacement from wintering refuge

habitats, as in the case of dredging, or impacts on spawning cycles that may result in adaptive

strategies to compensate for unfavorable habitat conditions. By identifying key habitat areas

combined with mortality information, we can begin to shift to an ecosystem based management

strategy which ultimately requires an understanding of how the two traditional management

arenas, harvest regulation and habitat protection, interact.










Table 2-3. Area (m2) and percent area monitored by VR2s for each habitat type in Sarasota Bay,
Florida.


Habitat type
Creek
Mangrove
Open Bay
Pass
Total


Number of VR2s


Monitored area m
706500
635850
282600
847800
2472750


2Percent Monitored
16.68
6.71
0.22
34.95
1.71










grow they tend to move from shallow riparian habitats to seagrass meadows, mangrove fringe,

and deeper estuarine areas (Gilmore et al. 1983). Adult snook often make use of passes from

estuarine waters into the open ocean for spawning (Muller and Taylor 2006). Despite the

species' broad use of habitat types, the overall distribution of adult snook has been found to be

highly correlated with the distribution of mangrove habitat (Gilmore et al. 1983). In addition,

snook are considered to be a cold water sensitive species with lower lethal temperature limits

between 6-130C (43-550F) (Marshall 1958; Howells et al. 1990). To avoid these lethal

temperatures during cool winter months, snook tend to seek thermal refuge in the warmer waters

of creeks and canals.

Acoustic telemetry was used in this study to examine seasonal movement and habitat use

patterns with the ultimate goal of gaining a better understanding of the ecological relationships

between a population of adult common snook and a variety of habitats within a large estuary in

southwest Florida. Relocations of individual adult snook were used to identify "key" habitats

that provide essential information needed to improve conservation management plans. I was

particularly interested in answering the following research questions:

* Question 1: Do snook demonstrate variable seasonal movement and habitat use patterns?

* Question 2: Do individual snook exhibit site fidelity in specific habitat type and location?

* Question 3: What are the impacts of large scale disturbance events on movement patterns
and habitat use?

* Question 4: Can inferences be made regarding survivorship by examining individual
movement and habitat use patterns of fish with known mortality fates?

Questions 3 and 4 were specifically related to an unusually large red tide bloom (Krenia

brevis) that occurred in summer 2005, and a dredging proj ect in a tidal creek system (Whitaker

Bayou) that began in late fall 2005. The red tide event provided a natural experiment to examine

snook movement and habitat use patterns before, during, and after the red tide bloom.





Gulf of Mexicoc


Figure 2-2. The VEMCO@ VR2 numbers and locations in Sarasota Bay, Florida. Table 2-2
gives the VR2 numbers with corresponding name and associated habitat type.


Legend
* VR2 location









Gulf side beach in July 2005 outside of New Pass while sampling snook carcasses of fish that

died during the red tide bloom.




Full Text

PAGE 1

1 EXAMINING SEASONAL MOVEMENT AN D HABITAT USE PATTERNS OF ADULT COMMON SNOOK By LAUREN LEE MARCINKIEWICZ A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2007

PAGE 2

2 2007 Lauren Lee Marcinkiewicz

PAGE 3

3 To my mother, father, and sisters fo r their unconditional love and support.

PAGE 4

4 ACKNOWLEDGMENTS I would like to thank my graduate advisor, Bi ll Pine, for which none of this would have been possible, along with the rest of my gra duate committee; Tom Frazer and Ken Leber. I would also like to thank everyone from the following organizations: University of Florida, Department of Fisheries and Aquatic Sciences : Jason Mo Bennett, Darren Pecora, Matt Laur etta, Towns Burgess, Jake Tetz laff, Jared Flowers, Elissa Buttermore, Ed Camp Florida Fish and Wildlife Conservation Commission : Behzad Mahoudi, Ron Taylor Mote Marine Laboratory : Nate Brennan, Meaghan Darcy, Dave Wilson I would also like to thank Ca ptain John Dixon for his amazing snook netting skills, and Ed Schmidt for his enthusiasm and countless hours of data crunching.

PAGE 5

5 TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................4 LIST OF TABLES................................................................................................................. ..........6 LIST OF FIGURES................................................................................................................ .........7 ABSTRACT....................................................................................................................... ..............8 CHAPTER 1 INTRODUCTION................................................................................................................... .9 2 MATERIALS AND METHODS...........................................................................................14 Study Site..................................................................................................................... ...........14 Determining Movement and Habitat Occupancy...................................................................14 Defining and Monitoring Available Habitats.........................................................................15 Analyses....................................................................................................................... ...........16 Assessing Seasonal Movement and Habitat Use Patterns...............................................16 Site Fidelity.................................................................................................................. ...18 Impacts of Habitat Disturbance on Movement and Habitat Use.....................................18 Relating Movement and Habitat Us e Patterns with Survivorship...................................19 3 RESULTS........................................................................................................................ .......25 Assessing Seasonal Movement and Habitat Use Patterns......................................................25 Site Fidelity.................................................................................................................. ...........27 Impacts of Habitat Disturbance on Movement and Habitat Use............................................27 Relating Movement and Habitat Us e Patterns with Survivorship..........................................28 4 DISCUSSION..................................................................................................................... ....40 5 CONCLUSIONS....................................................................................................................47 APPENDIX: ADDITIONAL TABLES AND FIGURES.............................................................49 LIST OF REFERENCES............................................................................................................. ..50 BIOGRAPHICAL SKETCH.........................................................................................................53

PAGE 6

6 LIST OF TABLES Table page 2-1 Total area (m2) and percent available for each habitat type in Sarasota Bay, Florida......20 2-2 VR2 habitat location with assigned nu merical location, indi cating geographical position around Sarasota Bay, and a ssociated VR2 habitat type.......................................20 2-3 Area (m2) and percent area monitored by VR2s for each habitat type in Sarasota Bay, Florida........................................................................................................................ ........21 3-1 Chi-square test ( =0.05) results to determine if th ere was a significant difference between observed and expected habita t use based on percent fish-days...........................31 3-2 Original capture habitat and location data for snook released within the detection range of a VR2................................................................................................................. ..32 A-1 Months included in each season, characterized by average monthly water temperature (C) for Sarasota Bay, Florida.......................................................................49

PAGE 7

7 LIST OF FIGURES Figure page 2-1 Sarasota Bay, Florida highlighted wi th major tidal tributaries and passes........................22 2-2 The VEMCO VR2 numbers and locations in Sarasota Bay, Florida. Table 2-2 gives the VR2 numbers with corresponding name and associated habitat type................23 2-3 This graph which shows relocations for an individual fish, 1936, depicts an example of fish-days based on daily relocation dataOverlapping relocations in various hab itat types, (1: creek, 2: m 2-4 Water temperature, following a dredging event which occurred in Whitaker Bayou in late fall 2004, for two creek systems.................................................................................24 3-1 Observed relocations of fish 1947 in Sarasota Bay, Florida. The solid arrow indicates where the fish was originally captured, tagged, and released. The dashed arrow indicates where the fi sh was last detected...............................................................34 3-2 Observed relocations of fish 1966 in Sarasota Bay, Florida. The solid arrow indicates where the fish was originally captured, tagged, and released. The dashed arrow indicates where the fi sh was last detected...............................................................35 3-3 Movement pattern based on relocations fr om VR2s for fish 1913. Refer to Table 2-2 for VR2 habitat location with assigned numerical locat ion, indicating geographical position around Sarasota Bay, and a ssociated VR2 habitat type.......................................36 3-4 Habitat use (percent fish-days) per season for Year 1 (2004/2005)..................................36 3-5 Habitat use (percent fish-days) per season for Year 2 (2005/2006)..................................37 3-6 Habitat use (percent fish-days) per season for Year 3 (2006/2007)..................................37 3-7 Average monthly water temperatures ( C) for an open bay area (New Pass) and a creek habitat (Bowlees Creek) in Sarasota Bay, Florida...................................................38 3-8 Habitat use (percent fish-days) at the or iginal capture habita t and location for snook (n=48). This graph is showing high site fidelity demonstrated by snook captured and released at specific habitat types (creeks and open bay)....................................................38 3-9 Seasonal habitat use (percent fish-days) in each of the tidal creeks before and after the dredging event in Whitaker Bayou, Sarasota Bay, Florida..........................................39 A-1 2005 and 2006 red tide ( K. brevis) cell counts for New Pass in Sarasota Bay, Florida....49

PAGE 8

8 Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science EXAMINING SEASONAL MOVEMENT AN D HABITAT USE PATTERNS OF ADULT COMMON SNOOK By Lauren Marcinkiewicz December 2007 Chair: William E. Pine Major: Fisheries a nd Aquatic Sciences The common snook, Centropomus undecimalis is an ecologically and economically important estuarine dependent pr edatory fish species found thr oughout south Florida. Despite increasingly restrictiv e management actions over the past 50 years, common snook populations are thought to have declined. Possible reasons fo r this decline are high ha rvest rates and loss of essential habitat related to coastal development. I evaluated habitat use and movement patterns for adult snook in seasons with and without large-scale enviro nmental (red tide blooms) and anthropogenic (dredging) disturbance events. Resu lts of my study support much of the literature on snook life history while providing new behavi oral information regarding movement, site fidelity, and habitat disturbances My study provides important information for conservation management purposes and improves the understanding of direct and indirect effects of habitat threats associated with anthropogenic and e nvironmental disturbances on snook populations. This understanding of habitat-species relationships is important because of the emphasis placed on managing habitat by various St ate and Federal agencies for the conservation of fish and wildlife resources.

PAGE 9

9 CHAPTER 1 INTRODUCTION Development and implementation of successful conservation and management strategies for terrestrial and aquatic organisms relie s on a sound understanding of their ecological requirements. In recent years, increasing attention has been gi ven to the habitat conservation approach with the motivation that protecting habitat will ensure populat ion viability. This approach, in fact, is a major component of many State and Federal mandates, including the Magnuson-Stevens Fishery Conservation and Mana gement Act (MSFCMA) for essential fish habitat (EFH), which requires using a habitat-orie nted and ecosystem-based approach to develop effective management and conservation plans. Sufficient habitat is a necessary requirement for survival of wildlife and aquatic populations (Morrison et al. 1992). Management of fisheries re sources typically follows two approaches: (1) regulating harvest to maintain sustainable populations and (2) preserving and improving species habitats through protective or restoration measur es. In the United States, the development of ecosystem based management, wh ere these two approaches are integrated into a single management strategy, has become the ma ndate for fisheries management (NRC 2006). For ecosystem based management to be su ccessful, an adequate understanding of the relationships between species and their habitat is necessary (Knapp and Owens 2005). This requires a thorough understandi ng of the types of habitats required for a species to live at all life stages, preferably through quantitat ive exploration of the species resource us e patterns (Oppel et al. 2004). As resources may include anything that an animal may ultimately require, such as foraging, refuge, and rearing habitats, monitoring patterns of interaction between species and their habitat may ultimately provide insight into the dynami c factors that drive viable

PAGE 10

10 populations. These patterns are directly relate d to individual behavi oral choices regarding movement and habitat interactions. In developing effective management strategies for a fishery, it is important to identify the linkages between individual fish behavior and habitat resources in or der to understand the implications of anthropogenic and environmen tal disturbances on populations. Physical disturbances related to coastal development, su ch as dredging and shoreline modification, are readily visible and obvious examples of habitat modification. However, less consideration is given to environmental disturbances such as harmful algal blooms (HABs e.g.; red tide blooms). HABs have been linked to widespread fish and marine mammal mortality events and are thought to be increasing in frequency a nd duration across much of southwest Florida (Mahadevan et al. 2005). HABs represent a unique case of habitat loss as they do not nece ssarily result in the loss of structural habitat. However, HABs may make otherwise suitable hab itat unusable (or even lethal) for extended periods of time. Red tide bloo ms, because of their toxic nature, are likely to force fish and other species to occupy sub-optimal habitats or elicit emigration from the system to areas not affected by the HAB event. Physical habitat alterations that result from dredging and development and other environmental disturbances such as HABs can have large impacts on fish populations. Reductions in growth, for example, can lead to lo wer fecundity and even survival rates which, in turn, can have marked population-level consequen ces. To understand the mechanisms that cause these population-level impact s, it is important to recognize beha vioral choices a nd potential bethedging strategies demonstrated by individuals. Individual choices rela ted to survival may include variable movement patterns or the use of alternative habitats to reduce an individuals

PAGE 11

11 risk of predation, vulnerability to fishing, or suscep tibility to lethal conditions Thus, it is critical to understand the interactions between a species and its habitat for effec tive conservation and management purposes. In general, the best method to identify habita t use and movement by an animal is through direct observation (White and Garrott 1990). When this is not feasible, which is often the case with aquatic organisms, acoustic tracking techni ques via telemetry can provide an adequate substitute. Telemetry studies provide insight into spatial and temporal use of habitats and can be a first step in identifying EFH (Arendt et al. 20 01). In the case of fishes, telemetry provides spatial and temporal tracking of individual m ovement and habitat use patterns which may ultimately reveal the most ecologically important habitats (Savitz et al. 1983). This method provides insight about key behavi ors such as foraging (Heithaus et al. 2002), activity patterns (Jadot et al. 2006), seasonal movement and site fidelity (Jackson and Hightower 2001). It also provides a means to estimate home ranges (M orrissey and Gruber 1993) and mortality rates (Bennett 2006). Ultimately, combining seasonal m ovement and site fidelity information with habitat-specific mortality estimates (both natural, M, and fishing, F) can facilitate predictions regarding the effects of habita t alterations on survivorship. Acoustic telemetry was used in this study to examine seasonal movement and habitat use patterns of adult common snook, Centropomus undecimalis. Common snook are an ecologically and recreationally important apex predator found throughout the tropi cal Caribbean basin including south Florida. In Fl orida, snook are abundant along th e Gulf of Mexico coast from Tampa Bay south to the Florida Keys and north to Cape Canaveral along the Atlantic coast (Muller and Taylor 2006). Througho ut different life stages snook use a range of habitats from offshore reefs to inland lakes and are generally considered diadromous (Rivas 1986). As snook

PAGE 12

12 grow they tend to move from shallow riparian habitats to seagrass meadows, mangrove fringe, and deeper estuarine areas (Gilm ore et al. 1983). Adult snook often make use of passes from estuarine waters into the open ocean for spawning (Muller and Taylor 2006). Despite the species broad use of habitat type s, the overall distribution of a dult snook has been found to be highly correlated with the dist ribution of mangrove habitat (G ilmore et al. 1983). In addition, snook are considered to be a cold water sensitive species with lower lethal temperature limits between 6-13C (43-55F) (Marshall 1958; Howe lls et al. 1990). To avoid these lethal temperatures during cool winter months, snook tend to seek thermal refuge in the warmer waters of creeks and canals. Acoustic telemetry was used in this study to examine seasonal movement and habitat use patterns with the ultimate goal of gaining a bett er understanding of the ecological relationships between a population of adult common snook and a va riety of habitats with in a large estuary in southwest Florida. Relocations of individual ad ult snook were used to identify key habitats that provide essential information needed to improve conservation management plans. I was particularly interested in answeri ng the following research questions: Question 1 : Do snook demonstrate vari able seasonal movement a nd habitat use patterns? Question 2 : Do individual snook exhibit site fidelity in specific habitat type and location? Question 3 : What are the impacts of large scale disturbance events on movement patterns and habitat use? Question 4 : Can inferences be made regarding survivorship by examining individual movement and habitat use patterns of fish with known mortality fates? Questions 3 and 4 were specifically relate d to an unusually large red tide bloom ( Krenia brevis ) that occurred in summer 2005, and a dredging project in a tidal cr eek system (Whitaker Bayou) that began in late fall 2005. The red tide event provided a natural experiment to examine snook movement and habitat use patterns be fore, during, and after the red tide bloom.

PAGE 13

13 Concurrent with this study and the red tide bloo m it was found that annual natural mortality rates were much greater than the natu ral mortality rates currently us ed in the snook stock assessment (Pine et al. 2007). Similarly, the dredging pr oject provided an experimental opportunity to examine snook movement and habitat use patterns in relation to physical habitat alteration. From previous quantitative sampling, Whitaker Bayou is thought to be a prominent nursery habitat and wintering area for both juvenile and adult snook (Brennan et al., in press). A layer of flocculent organic material in this system provides warmth during wi nter months due to decomposition and solar warming. Both experime nts provided the opportunity to examine the impacts of environmental and anthropogenic dist urbance events on habitat use and movement patterns of adult snook, which may have affect ed an individuals likelihood of survival.

PAGE 14

14 CHAPTER 2 MATERIALS AND METHODS Study Site Sarasota Bay (Figure 2-1) is a moderately sized, subtropical es tuary located along the southwest Florida coast. Saraso ta Bay was identified as an Es tuary of National Significance in 1987 by the United States Congress and has sinc e been included in the National Estuary Program. Sarasota Bay is approximately 44 km in the north-south direction and includes an area of about 114 km2. Sarasota Bay and its associated tidal tributaries, sub-bays, and canals are separated from the Gulf of Mexico by a series of narrow barrier islands, including Casey Key, Siesta Key, and Longboat Key, and connect with th e Gulf through a series of narrow passes. All sampling for this study was conducted betw een Cortez Bridge (Cortez, Florida) and Albee Bridge (Venice, Florida) at the southernmo st extent of the bay, just north of Venice Inlet (Figure 2-1). Within Sarasota Bay proper, th ere are three passes connecting Sarasota Bay and the Gulf of Mexico (Longboat Pass, New Pass, and Big Pass), as well as five major tidal tributaries (Bowlees Creek, Whitaker Bayou, Ph illippi Creek, North Creek, and South Creek, Figure 2-1). This study focused only on the wa ters of Sarasota Bay and did not include nearshore areas of the Gulf of Mexico. Determining Movement and Habitat Occupancy During fall 2004, 75 adult common snook were su rgically implanted with a uniquely coded, long-life (700-day), Vemco acoustic te lemetry tag (Vemco Ltd., Shad Cay, Nova Scotia, Canada). Three angler returned tags were later reused and implanted in newly caught snook (April 2005). These fish were referred to as batch 1. In summer 2006, five angler returned tags and one tag retrieved from a fish believed to have died of natural causes (red tide bloom), were reused to tag other adult snook. During this time, an additional 25 adult snook

PAGE 15

15 were tagged with 180-day tags. The group of fish (n=31) tagged in the summer 2006 was referred to as batch 2. All snook were tagged and released at the orig inal site of capture. Tagged snook were relocated using an arra y of underwater, autonomous VEMCO VR2 receivers (Vemco Ltd., Shad Cay, Nova Scotia, Ca nada). Acoustic receivers were programmed to record the unique tag code, date, and time when a tagged snook was within the monitoring range of the VR2. Listening stations were pos itioned strategically th roughout Sarasota Bay including the northern and southern extreme portions of the bay, passes, and major tidal tributaries (Figure 2-2). Data fr om the VR2s was retrieved on an 8 to 12 week schedule between October 2004 and March 2007. At least 29 receivers were constantly deployed in Sarasota Bay during the study period as part of this and other cooperative projects with Mote Marine Laboratory, Sarasota, Florida. Snook were also relocated manually using a Vemco VR100 receiver and directional hydrophone. These active searches were designed to sweep major areas of Sarasota Bay not covered by the VR2 array. Two tracking methods were used: (1) a hopscotch method in which tracking was conducted along the enti re shoreline of the bay at 300 m intervals and (2) a search method in which random GPS points were selected to monitor all areas of the bay. Manual tracking efforts were conducted opp ortunistically from fall 2004 to winter 2006 with the largest amount of effort occurring during summer 2005. Defining and Monitoring Available Habitats An existing classification of available habita t types in Sarasota Bay, developed for the Sarasota Bay National Estuary Program (SBNEP) (S erviss and Sauers 2003) was used to define four distinct habitat t ypes: creek, mangrove, open bay, and pass (Table 2-1). Habitat types for individual VR2 monitoring stations were assi gned by overlaying VR2 GPS coordinates onto preexisting GIS data layers. Each VR2 was give n a numerical assignment based on its location, a

PAGE 16

16 descriptive name and an associat ed habitat type (Table 2-2). The percent area of each habitat type monitored was calculated as: 100 _2 monitored area total areahabitatX VR (2-1) where areaVR2habitatX is the area of a monitored habitat type X with VR2 receiver coverage and total area monitored is the sum of the area of al l habitats monitored within theVR2 array (Table 2-3). The variable areaVR2habitatX was calculated as: 2* r N (2-2) where N is the number of receivers in the specif ic habitat, and r was the radius of the VR2 detection range (150 m) as determined from a series of range tests (Bennett 2006). Analyses Assessing Seasonal Movement and Habitat Use Patterns I summarized seasonal movement for individua lly tagged snook using relocation data from the VR2 array. Relocation data was infrequent fro m the manual tracking efforts, therefore, I did not include it in the analyses. I plotted indivi dual movement patterns within the bay system to determine if snook exhibit distinct seasonal movements. I used i ndividual movement patterns to describe generalized patterns exhibited by the po pulation. I also used the relocation data to compare seasonal habitat use patterns for the population of tagged snook in Sarasota Bay with previously documented snook life history informa tion. Habitat use was characterized by fishdays. A fish-day was defined as an individual date that a fish was recorded by a VR2 in a given habitat location (creek, mangrove, open bay, or pa ss). Consequently, as it was possible for a fish to occupy the four different habitat types in one day, an individual fish could have potentially contributed up to four fish-days per 24 hour time period. Figure 23 depicts an example of fishdays, based on daily relocations, for an indivi dual fish over a three month time period. An

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17 example where this particular fish, 1936, cont ributed two fish-days to the analyses, were on December 25, 2004 and March 15, 2005, where this fish was relocated in two different habitat types (mangrove and pass) on the same day. Two or more relocations, or hits at a VR2 were required to count as a fish-day to eliminate spur ious detections that are sometimes recorded by a VR2 from electronic equipment, marine mammals, or other noise sources (Clements et al. 2005; Heupel et al. 2006; Klimley et al. 1998). A series of 2 analyses were conducted to determine: (1) if there was a seasonal effect on habitat type use, i.e. were habitat use and s eason independent, and (2) if there was a difference between observed and expected habitat use for each season and year. Expected habitat use was defined as: days fish habitatX VRN monitored area total area_ _2 (2-3) where Nfish-days was the total number of observed fish-days in a season. Observed habitat use was the sum of the total number of fish-day s recorded for each habitat per season. The 2 test statistic was calculated as: 2= k i i i if f f1 2 ) ( (2-4) where if is the frequency, or number of counts, observed in class i(habitat type), and if is the frequency expected in class iif the null hypothesis is true (Zar 1999). All 2tests were conducted using the Statistical Analysis Syst em (SAS Institute 1996) and Microsoft Excel. Seasons were defined by average monthly wate r temperatures (Table A-1). Year 1 began in fall 2004 and included the winter, spring and summer seasons that followed. Relocations during this time were from batch 1 fish only. Year 2 began in fall 2005 and included the

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18 following winter, spring and summer seasons. Re locations during this time were from batch 1 fish and batch 2 fish (beginning in the summer season). Year 3 began in fall 2006 and included the following winter season. Relocations during this time were primarily from batch 2 fish as the battery life of the tags from the majority of batch 1 fish had expired. Site Fidelity Relocations of individual fish were examined to determine if site fidelity was evident based on the original capture habitat and location compared to other similar and different habitat types. Relocations were grouped by habitat type and characterized by fi sh-days per individual fish. To determine site fidelity at the original capture location, I required that only fish released within the detection range of a VR2 be considered in the analysis. I calculated percent fish-days spent at the site of capture for each individual snook included in the analysis. I inferred high site fidelity if the percent of fish-days was highest at the original capture habitat and location, for the entire time a fish was monitored. I also assessed individual creek site fidelity for fish captured specifically in Bowlees Creek (n=6 fish) and Whitaker Bayou (n=9 fish) and the single fish captured in South Creek. Impacts of Habitat Disturbance on Movement and Habitat Use I estimated habitat use by summing the total num ber of fish-days in ea ch habitat per season to determine if there was a difference in habita t use, based on percent fish-days, that may be related to the red tide bloom or the dredging treatments. For the red tide bloom, I examined habitat use within passes betw een the summer of this event (2005) and the summer of the following year (2006) when the duration of elev ated red tide cell counts was shorter (Figure A1). Snook use pass habitats as spawning sites in the summer and are known to aggregate in these areas for several weeks each year. Pass habitats also often have high red tide cell count levels because of their proximity to the Gulf of Mexico I expected percent habitat use in passes to

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19 increase in summer 2006 relative to 2005 because the duration of red tide cell counts exceeding a level that is considered lethal to fish (200,000 cells/liter) was higher in 2005 than in 2006. I expected snook to avoid passes during the high red tide events. To assess the impact of dredging, I examined if the dredging event which occurred in Whitaker Bayou led to differences in percent habi tat use before and afte r the event between the five tidal creeks. Snook are a cold water se nsitive species (Marshal l 1958) and Whitaker Bayou is a prominent wintering area for snook (Brennan et al., in press). Therefore, I expected habitat use to increase in other creek systems and decr ease in Whitaker Bayou, particularly due to the lower water temperatures within Whitaker Bayou compared to other creek systems, after dredging began (Figure 2-4). Relating Movement and Habitat Use Patterns with Survivorship I examined habitat use and movement patterns of fish with known mo rtality fates (fishing or natural). This included nine fish that were caught and had ta gs returned by anglers, and one fish believed to have died as a result of th e red tide bloom in summer 2005. I calculated the mean days-at-liberty for the fish harvested by anglers and compared patterns among fish with fewer days-at-liberty (<150 days) to those with a mean days-at-liberty 150 days. Days-atliberty was defined as the number of days a fish was known to be alive po st-capture, tagging, and release.

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20 Table 2-1. Total area (m2) and percent available for each habitat type in Sarasota Bay, Florida. Habitat type Area m2 Percent available Creek 4236249 2.95 Mangrove 9470858 6.58 Open Bay 127673723 88.78 Pass 2425627 1.69 Total 143806459 100.00 Table 2-2. VR2 habitat location with assigne d numerical location, i ndicating geographical position around Sarasota Bay, and associated VR2 habitat type. VR2 site Numerical assignment Habitat type Longboat Moorings (LBMM) 1 Open bay Longboat Pass 2-4 Pass Cortez Pass 5-7 Pass Tidy Island 8 Mangrove Bayshore 9 Mangrove Bowlees Creek (mouth) 10 Creek Bowlees Creek (inside) 11 Creek Haunted House 12 Open bay Johnny Pilings 13 Open bay Whitaker (mouth) 14 Creek Whitaker (inside) 15 Creek Fountain 16 Open bay Hudson Bayou 17 Mangrove Siesta Islands 18 Mangrove Phillippi ICW 19 Mangrove Phillippi Creek 20 Creek Coral Cove 21 Open Bay North Creek Outer 22 Mangrove North Creek Tunnel 23 Creek North Creek Pilings 24 Creek North Creek Upper 25 Creek Spanish Point 26 Mangrove South Creek (mouth) 27 Creek South Creek (inside) 28 Creek Pops Dock 29 Pass Big Pass 30-32 Pass Sunken Barge 33 Mangrove Backdock 34 Mangrove New Pass 35-36 Pass

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21 Table 2-3. Area (m2) and percent area monitored by VR2s for each habitat type in Sarasota Bay, Florida. Habitat type Number of VR2s Monitored area m2 Percent Monitored Creek 10 706500 16.68 Mangrove 9 635850 6.71 Open Bay 4 282600 0.22 Pass 12 847800 34.95 Total 35 2472750 1.71

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22 Figure 2-1. Sarasota Bay, Florida highlight ed with major tidal tributaries and passes.

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23 Figure 2-2. The VEMCO VR2 nu mbers and locations in Sarasota Bay, Florida. Table 2-2 gives the VR2 numbers with correspondi ng name and associated habitat type.

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24 1 2 3 4 12/04/0412/19/0401/03/0501/18/0502/02/0502/17/0503/04/0503/19/0504/03/05 DateHabitat type Relocations Figure 2-3. This graph which s hows relocations for an individual fish, 1936, depicts an example of fish-days based on daily relocation da ta. Overlapping relocations in various habitat types, (1: creek, 2: mangrove, 3: open bay, 4: pass) on a specific date, constitute multiple fish-days contributed by an individual fish. 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0 28.0 30.012/14/05 12/28/05 1/11/06 1/25/06 2/8/06 2/22/06 3/8/06 3/22/06Temperature ( C ) Bowless Creek Whitaker Bayou Figure 2-4. Water temperature, following a dredging event which occurred in Whitaker Bayou in late fall 2004, for two creek systems.

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25 CHAPTER 3 RESULTS Assessing Seasonal Movement and Habitat Use Patterns In examining the movement patterns of a ll individually tagged snook between fall 2004 and winter 2007 I observed two general movement patterns: (1) transient fish that traveled long distances to multiple habitats throughout th e year, and (2) resident fish that moved infrequently between habitats within a small geogra phic area. For example, fish 1947 was tagged and released in a mangrove habitat in the southern por tion of the bay along the eastern shoreline in fall 2004. This fish was repeatedly relocated for over a year and a half in various habitat types throughout the entire bay system including multiple creek, mangrove, and open bay areas in both the northern and sout hern portion of Sarasota Bay (Fi gure 3-1). This fish was last detected at an open bay VR2 in summer 2006. In contrast, fish 1966 was tagged and released in a creek habitat in the northeastern portion of the bay and was relocated primarily in its original capture creek and nearby mangrove habitat for approximately seven and a half months until it was last detected on a pass rece iver. Thus, I assumed that the fish emigrated from the study system (Figure 3-2). Larger scale movement patterns tended to occur primarily during the late spring and summer months for most fish. Th ese travel patterns ty pically involved a fish transitioning from a creek habitat in the northern porti on of Sarasota Bay and moving to a southern pass habitat. During the spring and early summer of 2005, 14 of 35 tagged fish demonstrated this type of movement patterns as fish would move out of a creek habitat in the northern bay to nearby habitats including other creeks, mangroves and open bay areas (e.g., fish 1913, Figure 3-3). Distances traveled to the nearby habitats duri ng this time, ranged between 0.6-3.0 km. The transitional movement to nearby habitats typically lasted for one month. During late June and

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26 early July these fish traveled to the southernmo st portion of the bay where they were detected on a VR2 that was located in the In tracoastal Waterway (ICW) just north of the entrance to Venice Inlet for varying time intervals. In most cases these fish would return to the same northern bay habitats where they were located earlier in the year. For a fe w fish (n=3), this pattern was demonstrated on an annual basis over a two-year time period. Straight-line, one-way distances for all tagged snook, between recorded relocat ions, ranged from zero (f ish that were only detected at one receiver location) to >30 km. All four monitored habitat types classified by SBNEP were used by adult snook throughout this study, although patterns of habitat use varied among seasons and years (Figures 3-4, 5, and 6). Results from chi-square analyses ( = 0.05) indicated a sign ificant dependence between habitat and season for Year 1 ( 2 = 2024.69, df = 9, p = < 0.0001), Year 2 ( 2 = 334.43, df = 9, p = < 0.0001), and Year 3 ( 2 = 55.12, df = 3, p = <0.0001). Hence, there was a general association of snook habitat use pa tterns with both ha bitat type and season. There was also a significant difference in the 2 analysis ( = 0.05) between expected and observed habitat occupancy for each season in years 1, 2, and 3 (Table 3-1). Throughout fall and winter, when water temperat ures in creek habitats were typically warmer than open water areas (Figure 3-7) habita t use, determined by fish-days from relocation data, for the tagged snook was highest in creeks. Over fifty-percent of all fall and winter observations during years 1 and 2 were in creek ha bitats. In spring, Y ear 1, habitat use was highest in mangroves and acc ounted for 39% of all observations. In spring, Year 2, habitat use was highest in creeks and account ed for 52% of all observations. Habitat use differed between the summers in years 1 and 2. In summer, Year 1, use was greatest in passes (34%). In summer, Year 2, mangrove habitat was used most often, accounting for 51% of all observations. Fall and

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27 winter of Year 3 were the last two seasons included in this study and during this time period habitat use was highest in cr eek and mangrove habitats (fal l: 38% creeks, 36% mangroves, winter: 37% creeks, 36% mangroves). Snook habitat use in open bay varied within a range of 021% among seasons and between years. Site Fidelity A table was constructed which included the da te of capture, size, capture location (VR2), capture habitat, and the percenta ge of fish-days at the original capture location for the 48 fish captured, tagged and released with in the detection range of a VR2 (Table 3-2). Data from this table was used to graph habitat use, based on per cent fish-days, to examine site fidelity for a specific habitat and location (Figur e 3-8). Overall, when all tagged fish released within the vicinity of a VR2 were included in the analysis, I found that site fidelity was highest among fish captured in creeks (63%) and open bay (69%) habitats. There were a total of sixteen fish captured and released in three of th e five creek habitats. Six of these fish were from Bowlees Creek. The mean proportion of relocated fish-days for these fish was 0.63 (SE 0.15). Nine fish were released in Whitaker Bayou. Habitat use based on the mean proportion of fish-days within Whitaker was 0.53 (SE 0.08). One fish was captured and released in South Creek. The propor tion of relocated fish-d ays within South Creek was 0.95. Although definitive conclusions are lim ited to the small numbers of fish captured within specific creeks, this data suggests that snook may demonstrat e high year round site fidelity to the specific creeks in which they were first captured. Impacts of Habitat Disturbance on Movement and Habitat Use I observed a large decrease in percent habitat use, based on fish-days, for snook in pass habitat between summer Year 1 (34%) and summe r Year 2 (9%). During the summer, use of creek and mangrove habitats by snook was higher in Y ear 2 than in Year 1 (Figures 3-4 and 3-5).

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28 In the summer of Year 2, mangrove habitat wa s used most often, accounting for 51% of all observed fish-days. Percent habitat use, based on fish-days w ithin creeks, decreased in Whitaker Bayou following the start of the large dredging event at the end of fall Year 2 (Figure 3-9). Percent habitat use in Whitaker Bayou decreased from 44% in fall and 39% in winter of Year 2 to 13% in fall and 0% in winter of Year 3. Simultane ously, percent habitat use in other creeks increased over the seasons following the dredging event. This was most dramatically observed within Phillippi Creek where percent habitat use increased from 13% in fall Year 2 to 53% in the fall Year 3. This pattern was also observed between the winter seasons where percent habitat use increased from 16% to 76%, betwee n years 2 and 3, respectively. Relating Movement and Habitat Use Patterns with Survivorship Nine fish were harvested by anglers during this study. The number of days-at-liberty from the original capture date to ha rvest ranged from approximately 100 to 340 days. All fish were originally captured, tagged, and released in the northern portion of Sara sota Bay. Relocations from these fish were also all in the northern po rtion of the bay. Appreciable movement was not observed for four of the harvested fish as they were relocated nearly 100% of the time at one open bay VR2 location (Longboat Marina and Moori ngs, VR2 1). Three of these fish were originally tagged near this VR2 (1907, 1917, and 1963). The other fish, 1937, was tagged approximately 2 km north of this location. Two fish, (1902 and 1909) we re tagged in mangrove habitat near VR2 33 between Lido Key and Big Pa ss. Fish 1909 was relocated 100% of the time at VR2 33. Fish 1902 utilized Big Pass until Januar y 26, 2005. This fish was not detected again until March 6, 2005 in Big Pass which suggests that it may have moved into the Gulf of Mexico during that time. Following this, habitat use was among mangroves near VR2 33 and Big Pass. The last detection of this fish before it was harvested in April 2005 was at VR2 33. Fish 1930

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29 was tagged in October 2004 approximately 650 m nor theast of a VR2 adjacent to Siesta Key. This fish was relocated in a mangrove habita t near this VR2 a month later during manual tracking efforts. Following this relocation, the fish was detected on VR2s moving north until it entered Whitaker Bayou. All subsequent relo cations were within Whitaker Bayou prior to harvest (February 2, 2005). The mean number of days-at-liberty for these seven fish was 128 days. The final two fish that were harvested had a higher number of mean days-at-liberty (310 days) than the other seven fish. Both fish were tagged on the same date in early November 2004. Fish 1932 was tagged in an open bay habitat in the northwest portion of the bay. While at liberty, this fish exhibited considerable move ment between its origin al capture location and several pass habitats. It was la st relocated in late August 2005 n ear the area in which it was first captured. Fish 1962 was tagged in a mangrove habita t in the northeast porti on of the bay. This fish moved between its original capture location and a creek ha bitat (Bowlees Creek) throughout the fall, winter, and early spring seasons. This fi sh was also relocated in various pass habitats throughout the summer, and returned to Bowlees Creek and surrounding mangrove habitats in the late summer. This fish was last reloca ted in late September 2005 within Bowlees Creek. One fish, 1916, was assumed to have died as a result of the red tide bloom in summer 2005. This fish was originally tagged in an ope n bay habitat in the northwest portion of the bay in November 2004. Relocations of this fish were infrequent within the first two months of when it was first captured with one to two fish-days near a VR2 where it was originally captured. Relocations remained infrequent during spring near a VR2 in mangrove habitat adjacent to Siesta Key. In the summer, relocations were concentrat ed in New Pass. This fish was found dead on a

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30 Gulf side beach in July 2005 outside of New Pa ss while sampling snook carcasses of fish that died during the red tide bloom.

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31 Table 3-1. Chi-square test ( =0.05) results to determine if there was a significant difference between observed and expected habita t use based on percent fish-days. Year Season 2 value d.f. p-value fall 423.4 3 < 0.0001 winter 2857.5 3 < 0.0001 spring 395.7 3 < 0.0001 1 summer 8.9 3 0.0300 fall 41 5.9 3 < 0.0001 winter 1075.9 3 < 0.0001 spring 146.8 3 < 0.0001 2 summer 450.3 3 < 0.0001 fall 140.4 3 < 0.0001 3 winter 106.7 3 < 0.0001

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32 Table 3-2. Original capture habitat and locatio n data for snook released within the detection range of a VR2. Fish ID Capture date Size (TL) mm Capture location (VR2) Capture habitat Percent fishdays at capture habitat and location 1646 8/18/2006 734 32 pass 3.0 1647 8/18/2006 694 32 pass 34.0 1648 6/23/2006 856 8 mangrove 0.0 1649 8/18/2006 739 32 pass 23.0 1650 6/23/2006 917 8 mangrove 57.0 1654 8/18/2006 817 32 pass 5.0 1656 6/23/2006 910 8 mangrove 27.0 1662 6/23/2006 662 8 mangrove 3.0 1663 8/18/2006 710 32 pass 43.0 1666 6/23/2006 644 8 mangrove 4.0 1906 10/12/2004 721 34 mangrove 12.0 1912 10/26/2004 663 18 mangrove 86.0 1913 12/2/2004 856 14 creek 53.0 1916 11/3/2004 689 1 open bay 81.6 1917 11/3/2004 714 1 open bay 97.8 1918 11/3/2004 707 1 open bay 99.5 1920 10/20/2004 932 11 creek 54.0 1922 11/3/2004 750 1 open bay 28.0 1923 11/3/2004 683 1 open bay 60.0 1924 10/28/2004 1100 8 mangrove 5.6 1926 11/3/2004 705 1 open bay 33.3 1931 10/20/2004 853 11 creek 20.0 1932 11/3/2004 720 1 open bay 87.9 1935 12/2/2004 819 14 creek 39.0 1936 10/21/2004 668 35 pass 81.0 1938 10/20/2004 816 11 creek 97.0 1941 11/3/2004 748 1 open bay 93.6 1943 12/2/2004 700 14 creek 81.0 1945 11/3/2004 683 1 open bay 63.8 1949 10/28/2004 712 8 mangrove 37.0 1950 10/20/2004 850 11 creek 92.0 1951 12/2/2004 722 14 creek 69.0 1955 12/2/2004 845 14 creek 71.0 1956 12/2/2004 670 14 creek 26.0 1957 11/3/2004 687 1 open bay 100.0 1958 10/26/2004 681 18 mangrove 85.0 1959 12/2/2004 761 14 creek 79.0 1961 11/2/2004 776 8 mangrove 6.6 1962 11/3/2004 856 13 open bay 13.0

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33 Table 3-2. Continued Fish ID Capture date Size (TL) mm Capture location (VR2) Capture habitat Percent fishdays at capture habitat and location 1963 11/3/2004 666 1 open bay 100.0 1965 11/22/2004 855 28 creek 95.0 1966 10/20/2004 896 11 creek 23.0 1967 10/21/2004 596 35 pass 82.0 1969 10/7/2004 596 10 creek 94.0 1971 12/2/2004 615 14 creek 1.0 1973 12/2/2004 851 14 creek 46.0 1975 12/3/2004 655 18 mangrove 89.0 51937 4/15/2005 741 1 open bay 0.0

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34 Figure 3-1. Observed relocations of fish 1947 in Sarasota Bay, Florida. The solid arrow indicates where the fish was originally cap tured, tagged, and released. The dashed arrow indicates where the fish was last detected.

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35 Figure 3-2. Observed relocations of fish 1966 in Sarasota Bay, Florida. The solid arrow indicates where the fish was originally cap tured, tagged, and released. The dashed arrow indicates where the fish was last detected.

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36 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31Dec-04 Jan-05 Feb-05 Mar-05 Apr-05 May-05 Jun-05 Jul-05 Aug-05 Sep-05 Oct-05 Nov-05 Dec-05 Jan-06 Feb-06 Mar-06 Apr-06 May-06 Jun-06 Jul-06 Aug-06 Sep-06MonthVR2 numerical assignmen t Figure 3-3. Movement pattern based on relocations from VR2s for fish 1913. Refer to Table 2-2 for VR2 habitat location with assigned nu merical location, indicating geographical position around Sarasota Bay, and associated VR2 habitat type. 0 10 20 30 40 50 60 70 FallWinterSpringSummer Seasons (2004/2005)Percent fish-days Creek Mangrove Open bay Pass Figure 3-4. Habitat use (percent fish-d ays) per season for Year 1 (2004/2005).

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37 0 10 20 30 40 50 60 70 FallWinterSpringSummer Seasons (2005/2006)Percent fish-days Creek Mangrove Open bay Pass Figure 3-5. Habitat use (percent fish-d ays) per season for Year 2 (2005/2006). 0 10 20 30 40 50 60 70 FallWinter Seasons (2006/2007)Percent fish-days Creek Magrove Open bay Pass Figure 3-6. Habitat use (percent fish-d ays) per season for Year 3 (2006/2007).

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38 10 12 14 16 18 20 22 24 26 28 30 32Dec-05 Jan-06 Feb-06 Mar-06 Apr-06 May-06DateTemperature ( C ) New Pass Bowlees Creek Figure 3-7. Average mont hly water temperatures ( C) for an open bay area (New Pass) and a creek habitat (Bowlees Creek) in Sarasota Bay, Florida. 0 10 20 30 40 50 60 70 80 CreekMangroveOpen bayPass Habitat typePercent fish-days at release site Figure 3-8. Habitat use (percent fish-days) at the original captu re habitat and location for snook (n=48). This graph is showing high site fidelity demonstrated by snook captured and released at specific habitat types (creeks and open bay).

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39 Figure 3-9. Seasonal habitat use (percent fish-days) in each of the tidal creeks before and after the dredging event in Whitaker Ba you, Sarasota Bay, Florida. 0 10 20 30 40 50 60 70 80 Fall 1Winter 1Spring 1Summer 1Fall 2Winter 2Spring 2Summer 2Fall 3Winter 3SeasonPercent fish-days Bowlees Creek North Creek Phillippi Creek South Creek Whitaker Dredging begins in Whitaker Bayou

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40 CHAPTER 4 DISCUSSION Along with confirming results from several life history studies, including the association of habitat use with specif ic habitat types (e.g., Gilmore et al. 1983 and Muller and Taylor 2006), new insights have been gained regarding habitat site fidelity and variable movement patterns of adult common snook. These new findings provide insight into individu al behaviors of snook which may be adaptive strategies that increase an individuals chance of survival by decreasing susceptibility to possible sources of mortality (harvest, HABs, and displacement from refuge habitats). For example, it appeared that there was a distinct seasonal movement and habitat use pattern demonstrated by indivi dual snook which may have increas ed the likelihood of these fish surviving the large scale red tide bloo m in Sarasota Bay, during summer 2005. Survivors of the red tide bloom generally sp ent extended periods of time through the fall and winter in the creek habitats found in north ern Sarasota Bay. Ho wever, during summer 2005 many of these fish were found in the most southe rn areas of Sarasota Bay around Venice Inlet. This may have increased the probability of these fish surviving th e red tide bloom during summer 2005 because southern Sarasota Bay appeared to have lower levels of fish kills (Bennett 2006), likely due to the higher exchange rate with the Gulf of Mexico, and increased availability of freshwater over areas in the so uthern regions of Sarasota Bay from creeks. Some fish were last detected at the Venice Inlet location duri ng the summer 2005 and were not relocated until several months later at this same location. Thes e fish may have either exited the bay system into the Gulf of Mexico or traverse d out of the VR2 array detection range from the Venice area of Sarasota Bay to other bay and creek systems lo cated further to the south (Roberts Bay, Curry Creek, Lemon Bay and Alligator Creek, for example) This would not be unlikely as this study has shown a number of indi vidual fish moving distances 30 km. In addition, at least three fish

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41 exhibited the previously describe d pattern (northern creeks to sout hern passes in the summer) for two consecutive years. This s uggests a potentially beneficial behavioral strategy for these individual fish making them less susceptible to mortality associated with major red tide blooms in pass habitats in the summer spawning months. Overall, fish that were identified as natural mortalities from the red tide bloom in Bennett (2006) were most frequently relocated on pass receivers in the northern bay. During the summer 2005 red tide bloom, it appeared that fish kills were greatest in the northern portion of Sarasota Bay. Fish that were detected in pass habitat in Ye ar 1 (red tide bloom) that survived to the following summer were part of the group of fish th at showed increased utilization of creek and mangrove habitats in the summer of Year 2. This decline in pass habitat use may be related to a decrease in the number of fish that were available to be monitored in the system, but it could also indicate that individual fish may not return to spawning areas with the same frequency each year. Jorgensen (2006) showed that Atlantic cod Gadus morhua are annual spawners when young. However, as the fish mature they exhibit skip -year spawning. Older fi sh, in fact, spawn only every second or third year. Female Gulf sturgeon, Acipenser oxyrhincys desotoi may also skip spawn as they are thought to spawn on 34 year intervals (Pine et al. 2001). A multi-year spawning interval such as this could be advantageous for common snook for several reasons. First, spawning is energetically very costly, part icularly for females (Jorgensen 2006) and the energetic demands of producing the la rge gametes of adult snook are likely high. Second, pass habitats are likely the most risky habitats that adult snook occupy. Pass habitats of Sarasota Bay are generally the first to be exposed to red tide blooms originating from the Gulf of Mexico. Additionally, pass habi tats are more likely than othe r habitats in the bay to support potential predators of adult s nook including a variety of shark sp ecies (C. Simpfendorfer, Mote

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42 Marine Laboratory, personal communication) an d dolphins (R. Wells, Mote Marine Laboratory, personal communication). Thus, it seems reasonable that adult snook would minimize their time in the risky habitats. Although fu rther research is required to confirm this, skip-spawning may be a potentially advantageous evolutionary tr ait exhibited by some s nook in Sarasota Bay, especially during periods when enviro nmental conditions are unfavorable. Unfavorable habitat conditions that are a resu lt of anthropogenic disturbances, such as dredging, may lead to displacement. This di splacement could potentially have negative population level impacts by increasi ng an individuals susceptibil ity to sources of mortality including exposure to predators (Walters and Ju anes 1993) or lethal environmental conditions. Cederholm and Reid (1987) summarized the im pacts of forest management via logging on Northwest coho salmon Oncorhynchus kisutch populations. They describe decreases in resilience mechanisms (e.g. excess spawning and a bundant fry) and survival over a variety of life stages which resulted from an increase in suspe nded sediments and a decrease in refuge habitats. A decrease in resiliency and survival from an thropogenic habitat degrad ation such as this, combined with overfishing, resulted in an overall decrease in coho salmon stocks. This result led Cederholm and Reid (1987) to suggest an integrat ed approach to natural resource management which includes the protection of habitats used by fish through the combined efforts of the fishery and forestry industries. During this project, Whitaker Bayou was subj ect to a major physical modification when a channel was dug to increase boat access to a ne w marina complex. This dredging project removed a layer of flocculent organic material that helped to keep Whitaker Bayou warm during winter months due to decomposition and solar warm ing. Before dredging began, the percent of habitat use in Whitaker Bayou was relatively hi gh, ranging between 44%, in fall Year 2, and

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43 39% in winter Year 2. After dredging began, habitat use decreased within Whitaker Bayou and increased among other creek systems, most notably in Phillippi Creek. This, however, may be an affect of a decrease in batch 1 fish (due to mortality and emigration), that had site fidelity towards Whitaker Bayou, still a live and monitored in 2006. Add itionally, most of the 25 fish tagged in summer 2006 were initially captured in mangrove and pass hab itat approximately 4km or less from the mouth of Phillippi Creek. Neve rtheless, four of the ni ne fish relocated in Whitaker Bayou in winter Year 1 we re relocated the following winter in other habitats. Three of these fish were relocated in other creek systems (Bowlees Creek or Philli ppi Creek). The fourth fish was relocated primarily in a mangrove habitat near Siesta Key Island. Therefore, it appeared that some individual snook demonstrated adap tive strategies in res ponse to displacement by moving to other creek or habitat areas. These are important findings because Whitake r Bayou is a rearing habitat for juvenile snook and a known wintering location for snook of all sizes (Brennan et al., in press). The loss of this flocculent bottom material likely led to the cooler wint er temperatures in Whitaker Bayou which potentially eliminated this creek habitat as a winter refuge. The decrease in water temperature in Whitaker Bayou compared to Bo wlees Creek post-dredging (Figure 2-4) is suggested as a factor leading snook to seek th ermal refuge in other creek systems. The possibility of impacts at the individual level, which affect populations, su ch as reduced growth, recruitment, and survival due to habitat degrad ation and/or loss, shoul d be considered when making management decisions regardi ng habitat and species protection. Issues regarding habitat protection, as well as fisheries management, are often closely linked to individual habitat site fidelity. Evidence of site fidelity has been widely documented in relation to the importance in deve loping management strategies of spatially explicit populations

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44 in reservoirs (e.g., Jackson and Hightower 2001) and marine reserv es (e.g., Meyer et al. 2000). The suggestion that snook demonstrate high site fi delity to specific hab itats in a bay system poses a concern to either maintain or impr ove these habitats which ultimately provide advantageous resources (e.g., food sources and/or refuge) during certain life history stages. In particular, it appeared that snook exhibit high site fidelity toward specific creeks primarily during winter seasons and specific pass habitats during summer seasons. This suggests the significance of individual habitat types and locations as poten tially important year-round habitats for feeding, breeding, and refuge. High site fidelity may also prove to be disadva ntageous in certain instances. For example, it appeared that the majority of snook harvested by anglers demonstrated hi gh site fidelity to the open bay habitat near VR2 1, located in the northe rn portion of the bay. A stationary strategy such as this may be beneficial to conserving energy while foraging. These fish, however, may ultimately be more susceptible to harvest by angler s. Fish that exhibited high site fidelity to open bay areas and creeks had fewer days-at-large th an fish that moved between habitat types. Therefore, potential inferences could be made regarding increased chances of survival based on site fidelity although data such as angler effort would also need to be examined to make more concrete predications about survivorship. Another possibly disadvantageous habitat use strategy was related to pass site fidelity during the spawning season (summer 2005). The one fish that was found dead, presumably as a result of the red tide bloom, most likely came to New Pass to spawn but was unable to survive the extremely exaggerated red tide cell counts during that time. Natural mortality due to the red tide bloom was also suspected, but not confirmed, for seven other fish. These latter fish were last detected within northern bay passes in su mmer 2005. Snook that did not utilize passes in the

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45 northern portion of the bay during summer 2005 to spawn had perhaps increas ed their chances of survival by escaping areas of the bay with the mo st concentrated red tide cell counts. This demonstrates how site fidelity, as in the cas e of spawning location, could have large-scale population impacts, i.e., genetic di versity of the populat ion could be lowered over time if fish that spawn in the northern passes are more suscep tible to mortality events while fish who spawn in southern pass are less impacted. Overall, I found that snook use a variety of ha bitat types and spatial locations, and exhibit a range of seasonal movement patterns. This dive rsity in behavior reduces the likelihood of any one cataclysmic event, such as a massive red tide bloom, killing all adult snook in Sarasota Bay. However, at least one tagged fish (1965) tagged in fall 2004 remained in the original creek where it was captured throughout the two y ear time period this fish was monitored. That creek habitat (South Creek) is located in the southern portion of Sarasota Bay. Occas ionally this fish was relocated on the pass VR2 near Venice Inlet durin g the summer seasons, but generally this fish appeared to move very little fr om the creek where it was originally captured. This type of behavior may have ultimately c ontributed to the survival of th is fish by decreasing its exposure to both fishing and natural (red tide) mortality. Similar variation in individual fish behavior has been noted in other systems (Gilliam and Fraser 2001). Adult snook used habitats in varying proportion compared to available habitat. This, however, was based on the analysis that the availabl e habitat, as well as th e expected habitat use, was equal to the proportion of each habitat type monitored by the VR2 array. VR2s were not randomly placed throughout the bay as this study was originally designed to estimate snook mortality rates and therefore necessary to relo cate fish (see Bennett 2006). For example, open bay, which makes up the majority of all available habitats in Sarasota Bay, had the smallest

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46 amount of VR2 coverage. This led to open bay becoming the sma llest proportion of monitored habitat, in terms of r eceiver coverage and total available habitat. Although this contributed a bias within the analysis, it appeared from the mo vement relocation data that open bay habitat was used primarily as transitional habitat or as a movement corridor, as opposed to the other habitat types where relocations occurred more often and for longer periods of time. In addition, only four habitat types (creek, mangrove, open bay, an d pass) classified by SBNEP were considered in this study. Other more fine scale habitat types such as oyster bars or seagrass may be considered for future work.

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47 CHAPTER 5 CONCLUSIONS This telemetry study provides insight into spa tial and temporal patter ns of habitat use and may serve as a first step towards identifying esse ntial fish habitat (Are ndt et. al 2001) for snook in Sarasota Bay, Florida. In this study, the relo cations of individual fish were used as a metric to identify key habitats used by common snook. This is particularly important in linking the use of critical seasonal habitats, such as winter cr eek systems and summer spawning habitats, with environmental and anthropogenic th reats in Sarasota Bay. Bo th scenarios of physical and environmental disturbances can lead to population level impacts within an aqua tic ecosystem. These impacts may include reduced growth of indi viduals, recruitment, and survival in an area where a disturbance has occurred. It is therefore important to recognize behavioral choices and potential bet-hedging strategies de monstrated by individuals, such as movement and habitat use, as they may ultimately provide insight into factors contributing survival. These new findings provide insight into i ndividual behaviors of snook which may be adaptive strategies that contribute to an i ndividuals chance of survival by increasing or decreasing susceptibility to possible sources of mortality (e.g., harvest, HABs, and displacement from refuge habitats). For example, it appeared that there was a distinct seasonal movement and habitat use pattern demonstrated by individual snook which may have increased the likelihood of these fish surviving the large scal e red tide bloom in Sarasota Bay. The fish that survived the bloom transitioned from northern cr eek habitats to the southern ex tent of the bay at Venice Inlet during the summer months whereas the fish that most likely died as a result of the red tide bloom used passes in the northern bay. The significance of this study is that it improves our understa nding of spatial and temporal relationships between an aquatic species and a variety of habitats. This study also documents

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48 findings on movement and habitat use in relation to anthropogenic and environmental sources of habitat loss. Implications of habitat loss can include displacement from wintering refuge habitats, as in the case of dredging, or impact s on spawning cycles that may result in adaptive strategies to compensate for unfavorable habi tat conditions. By iden tifying key habitat areas combined with mortality information, we can be gin to shift to an ecosystem based management strategy which ultimately requires an understand ing of how the two tr aditional management arenas, harvest regulation and ha bitat protection, interact.

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49 APPENDIX ADDITIONAL TABLES AND FIGURES Table A-1. Months included in each season, characterized by average monthly water temperature (C) for Sarasota Bay, Florida. Season Months Average water temperature ( C) Fall October, November 24.6 Winter December, January February, March 18.1 Spring April, May 24.1 Summer June, July August, September 29.6 0 2,000,000 4,000,000 6,000,000Jan-05 Feb-05 Mar-05 Apr-05 May-05 Jun-05 Jul-05 Aug-05 Sep-05 Oct-05 Nov-05 Dec-05DateRed tide cell counts/liter 2005 2006 Observed fish mortality Figure A-1. 2005 and 2006 red tide ( K. brevis) cell counts for New Pass in Sarasota Bay, Florida.

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50 LIST OF REFERENCES Arendt, M. D., J. A. Lucy, and T. A. Munroe 2001. Seasonal occurrenc e and site-utilization patterns of adult tautog, Tautoga onitis (Labridae), at manmade and natural structures in lower Chesapeake Bay. Fishery Bulletin 99:519-527. Bennett, J. P. 2006. Using acoustic telemetry to estimate natural and fishing mortality of common snook in Sarasota Bay, Florida. Masters thesis. University of Florida, Gainesville. Brennan, N.P., C.J. Walters and K.M. Leber. In Press. Manipulations of stocking magnitude: addressing density-dependence in a juvenile cohort of common snook, Centropomus undecimalis Reviews in Fisheries Science. Clements, S., D. Jepsen, M. Karnowski, and C.B. Schreck. 2005. Optimization on an acoustic telemetry array for detecting transmitter implante d fish. North American Journal of Fisheries Management 25:429-436. Gilliam, J.F. and D.F. Fraser. 2001. Movement in corridors: enhancement by predation threat, disturbance, and habitat st ructure. Ecology 82:258-273. Gilmore, R. G., C. J. Donahoe and D.W. C ooke. 1983. Observations on the distribution and biology of the common snook, Centropomus undecimalis (Bloch). Florida Scientist 46:313-336. Heithaus, M. R., L. M. Dill, G. J. Marshall, and B. Buhleier. 2002. Ha bitat use and foraging behavior of tiger sharks ( Galeocerdo cuvier ) in a seagrass ecosystem. Marine Biology 140:237248. Heupel, M.R., J.M. Semmens, and A.J. Hobday. 2006. Automated acoustic tracking of aquatic animals: scale, design and deployment of listeni ng station arrays. Marine and Freshwater Research 57:1-13. Howells, R. G., A. J. Sonski, P. L. Shafla nd, and B. D. Hilton. 1990. Lower temperature tolerance of snook, Centropomus undecimalis Short Papers and Notes. Northeast Gulf Sciences 11(2):155-158. Jackson, J. A., and J. E. Hightower. 2001. Reser voir striped bass movement s and site fidelity in relation to seasonal patterns in habitat quality. North American Journal of Fisheries Management 21:34-45. Jadot, C., A. Donnay, M. L. Acolas, Y. Cornet, and M. L. Bgout Anras. 2006. Activity patterns, home-range size, and ha bitat utilization of Sarpa salpa (Teleostei: Sparidae) in the Mediterranean Sea. Journal of Marine Science 63:128-139. Jorgensen, C., B. Ernande, O. Fiksen, and U. Dieckmann. 2006. The logic of skipped spawning in fish. Canadian Journal of Fish ies and Aquatic Science. 63:200-211.

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51 Klimley, A.P., F. Voegeli, S.C. Beavers, and B. J. Le Boeuf. 1998. Automated listening stations for tagged marine fishes. Marine Technology Society Journal 32:94-101. Knapp, C. R., and A. K. Owens. 2005. Home ra nge and habitat associations of a Bahamian iguana: implications for conserva tion. Animal Conservation 8:269-278 Marshall, A. R. 1958. A survey of the snook fishery of Florida, w ith studies of the biology of the principal species, Centropomus undecimalis (Bloch). Florida Board of Conservation Marine Research Laboratory Technical Series Number 22. Meyer, C. G., K. N. Holland, B. M. Wetherbee, and C. G. Lowe. 2000. Movement patterns, habitat utilization, home ra nge size and site fidelity of whitesaddle goatfish, Parupeneus porphyrus in a marine reserve. Environmental Biology of Fishes 59:235-242. Morrison, M. L., B. G. Marcot, and R. W. Mannan. 1992. Wildlife-habitat relationships: concepts and applications. Univers ity of Wisconsin Press, Madison. Morrissey, J. F., and S. H. Gruber. 1993. Home range of juvenile lemon sharks, Negaprion brevirostris. Copia 2:425-434. Muller, R. G. and R. G. Taylor. 2006. Th e 2005 stock assessment update of common snook, Centropomus undecimalis Fish and Wildlife Conservati on Commission, Florida Marine Research Institute, St. Petersburg. Oppel, S., H. M. Schaefer, V. Schmidt, and B. Schrder. 2004. Habitat selection by the paleheaded brush-finch ( Atlapetes pallidiceps ) in southern Ecuador: imp lications for conservation. Biological Conservation 118:33-40. Pine, W. E., III, M. S. Allen, and V. J. Dreitz. 2001. Population viability of the Gulf of Mexico sturgeon: Inferences from capture-recapture a nd age-structured models Transactions of the American Fisheries Society 130:1164-1174. Pine, W. E., III, L. L. Marcinkiewicz, and J. P. Bennett. 2007. Examining adult snook habitat occupancy, movement and exploita tion rate patterns in Sarasota Bay, Florida. Florida Fish and Wildlife Conservation Commission, St. Petersburg. Rivas, L. R. 1986. Systematic review of the perciform fishes of the genus Centropomus Copeia 1986:579-611. SAS Institute. 1996. SAS users guide: statistics, version 6. 4th edition. SAS Institute, Cary, North Carolina. Savitz, J., P. A. Fish, and R. Weszely. 1983. Habitat utilization and movement of fish as determined by radio-telemetry. Jour nal of Freshwater Ecology 2:165-174.

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52 Serviss, G. M., and S. Sauers. 2003. Sarasota Bay juvenile fisheries habitat assessment. Sarasota Bay National Estuary Program, Sarasota. Walters, C.J. and F. Juanes. 1993. Recruitment lim itation as a consequence of natural selection for use of restricted feeding ha bitats and predation risk take n by juvenile fishes. Canadian Journal of Fisheries and A quatic Sciences 50:2058-2070. White, G. C., and R. A. Garrott. 1990. Analysis of wildlife radio-tracking data. Academic Press. San Diego, California. Zar, J. H. 1999. Biostatistical analysis, fourth edition. Prentice Hall. Upper Saddle River, New Jersey.

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53 BIOGRAPHICAL SKETCH Lauren Lee Marcinkiewicz was born in Miami, Florida. However, she grew up primarily in Massachusetts. Lauren received her B.S. in marine biology from the University of California, Santa Cruz, in 2001. After graduation, she return ed to Massachusetts and worked as an observer on commercial ground fishing boats. In 2004, Laur en moved to Sarasota, Florida, where she worked as a technician under the supervision of Dr. William E. Pine, III at Mote Marine Laboratory. In August 2004, Laur en joined Dr. Pine to begin her masters research at the University of Florida, Department of Fisherie s and Aquatic Sciences. Lauren completed her masters research in 2007.