The science and significance of...
 The science and significance of...
 Fishing for success
 Mortality of the common snook

Group Title: Waterworks
Title: Waterworks. July, 2006.
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00067314/00013
 Material Information
Title: Waterworks. July, 2006.
Uniform Title: Waterworks
Physical Description: Serial
Creator: Institute of Food and Agricultural Sciences
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Publication Date: 2006
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00067314
Volume ID: VID00013
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Table of Contents
    The science and significance of reef fisheries habitat
        Page 1
    The science and significance of reef fisheries habitat
        Page 2
    Fishing for success
        Page 3
    Mortality of the common snook
        Page 4
        Page 5
        Page 6
Full Text

Newsletter of the UF/IFAS Department of Fisheries and Aquatic Sciences July 2006

t's intuitively obvious that habitat is
important to fishes and the fisheries
they support, and that quality of habitat
matters. It's much less obvious what
exactly constitutes habitat quality and
how best to account for it in fisheries

This is especially true for marine fishes
like gag grouper that occupy patchy
natural hard-bottom, rock outcrops and
ledges across a broad continental shelf.
Any grouper fisherman worth his or her
salt has a closely-guarded collection of
GPS coordinates and an electronic fish
finder (a.k.a. depth sounder) to locate
bottom features where they expect to
catch fish. And high quality grouper
habitat could be defined by where
fishers get their best catches. However,
that may or may not identify the habitat
characteristics and locations that
actually contribute the most to sustain
a broader fish population, particularly

juvenile female gag on patchy natural hard
bottom habitat.

when fisheries are fully exploited and
fishermen direct their efforts among
habitat patches to maintain their catch.

Increasingly, fisheries managers need
to know scientifically what constitutes
habitat quality and to understand
how and why reef fish, like gag, use
habitats of variable quality across
the continental shelf. Our program is
creating this basic knowledge with very
practical and immediate applications
to fisheries issues, such as occur with
the popular use of artificial reefs, the
identification of essential fish habitat
(EFH) and the development of spatially
explicit population models for fisheries

Habitat Issues Warranted Research

We got our start, and were afforded the
opportunity to do field experiments at
a large, real-world scale because of the
issues raised about artificial reefs in the
1980's. In essence, artificial reefs have
long been popular among recreational
fishermen because they increase their
catch and create reef fishing sites where
there had just been sand bottom. The
popular belief had been that artificial
reefs created more habitats that
produced more food, which produced
more fish. Indeed, both the catch rates
and densities of fish tended to be greater
on artificial reefs than on natural reefs

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in a region. However, fisheries scientists
reasoned that exploited fish populations
were already harvested to well below
the levels previously supported by the
existing natural habitat, so logically such
reef fishes couldn't be habitat limited
-artificial reefs might simply attract
these fish from elsewhere making them
easier to catch without benefiting the
population. This debate became known
as the Attraction-Production Question;
do artificial reefs merely attract fish or
produce them?

In 1990 we designed the Suwannee
Regional Reef System (SRRS) as an
unprecedented experiment to help
answer the Attraction-Production
Question scientifically. The SRRS
was constructed offshore of Levy
and Dixie Counties during 1991-
1993 with funding through the State's
Artificial Reef Program, now in the
Florida Fish and Wildlife Conservation
Commission's Division of Marine
Fisheries Management. Our SRRS
research was well underway when
Congress passed the Sustainable
Fisheries Act of 1996, with provisions
that required the identification and
management of essential fish habitat
(EFH) for all federally managed fisheries.
And while much was known about the
distributions of fishes among general
habitat types, very little was actually
known about habitat preferences and
how habitat affected reef fish growth,
survival and reproduction. Because of
the experimental rigor built into the
SRRS, and the ecological hypotheses
being tested, the same research
being done to address the Attraction-
Production Question also directly
addressed research needs for EFH,
particularly for gag grouper.


A Grouper Worth Knowing

Gag, Mycteroperca microlepis, is among the most important
recreational and commercial fishes in the southeastern

total length, with egg production strongly related to their size.
Our own research has concentrated on the pre-reproductive
females on the shallow shelf because their habitat selection
and associated variation in growth and condition could affect
subsequent reproduction in several ways.

U.S. For instance, the Florida gag landings for 2003 totaled Some major results from the first decade of SRRS research have
6,579,284 pounds, of which 57% was recreationally caught recentlybeensynthesizedinthejournal EcologicalApplications
and 89% landed along the Florida (see Lindberg et al. 2006). In summary, gag demonstrated
Gulf coast (source, FWC Fish and density-dependent habitat selection, preferring shelter even at
Wildlife Research Institute). Gag the expense of growth which was enhanced on the smaller,
are also important ecologically as a less preferred experimental patch reefs. Available shelter
top resident predator on reefs, limited gag density, which in
particularly where they reside in turn regulated their growth
high densities. and condition (i.e., weight
adjusted for length). Pre-
Interestingly, gag have a complex reproductive females resided
life history in which they all on reefs for an average of
begin as females and only a small 9.8 months, but the duration
fraction later change sex to males. Gag were implanted with transmitters to measure their residency, home greatly depended on patch
Spawning takes place in late rangeandhoming. reef size and spacing (i.e.,
winter aggregations well offshore along the shelf-edge break. the habitat patchiness of the landscape). After they emigrated,
Larval gag are transported by wind-driven currents to seagrass tagged gag caught by fishers were mostly west-northwest
beds and structured shallow-water habitats along the coast, of the SRRS, with 12.5% of the returns coming surprisingly
where they settle and grow as young-of-the-year juveniles. from the western Gulf of Mexico. In other studies, SRRS gag
In the fall of their first year they leave these nursery grounds demonstrated home ranges averaging about 380 yards across
for shallow shelf habitats. Pre-reproductive females up to 5 and an ability to home from almost 2 miles away (Kiel 2004).
years old reside on the patchy reef habitats of the shallow We also found that prey consumption by gag was density-
continental shelf before joining the spawning stock along the dependent (D. Murie et al. unpublished data), and it appears
outer shelf. At the time of their first reproduction females can that their activity levels are too (M. Butler et al. unpublished
range from 3 to 6 years old and anywhere from 22 to 38 inches data). The bulk of their prey also came from off-reef. Habitat

structure, spatial layout and behavior affected the growth
performance of the pre-reproductive gag, and this apparently
involved a trade-off with their risk of natural mortality.
However, it's still an open question as to how much regulation
of the gag population actually occurs at this intermediate life
history stage.

In a very practical experiment the exact locations for some
SRRS sites were released to the fishing public in November
1996. By the next summer virtually all legal-sized gag were
gone from the published reef sites, with little change at the
unpublished sites. Six to eight years later unpublished sites,
and especially those with the largest and most concentrated
patch reefs, showed reduced numbers of legal-sized gag, and
on some reef types even reduced numbers of sub-legal gag
(Larsen 2005). We concluded that (1) fishing effort is directed
mostly to reefs that are easiest to find and easiest to fish, (2)
detailed geographic information about fisheries habitat can
substantially increase fishing mortality, and (3) small, widely
scattered patch reefs could enhance fish growth, as noted
above, while passively controlling fishing pressure.

Interesting Artificial Reef Facts

* Florida has approximately 2,300 permitted artificial reef
sites located off 33 counties.

* 30 to 70 new public artificial reefs are constructed
annually in waters around Florida.

* Local governments build artificial reefs with State grants-
in-aid and local funding.

* The State of Florida has spent over $13.5 million on
artificial reefs over the past 23 years.

* In 2001, the annual recreational use value of artificial
reefs off Palm Beach, Broward, Dade and Monroe Counties
was estimated to be $84.6 million, compared to $228 million
for the natural coral reefs of the region. Expenditures
associated with artificial reefs supported about 27,000
jobs in the 4-county region.

* In 1998, the annual recreational use value of artificial
reefs off Escambia, Santa Rosa, Okaloosa, Walton and Bay
Counties was estimated to be $19.7 million. The associated
expenditures supported more than 8,000 jobs in the 5-
county region.

Faculty Focus

I shlDEj oorP

Created in 1993 tie Fi.-hi.n? or
Success proram'ii \\11 iI 'ti'all
designed as a menetornc ? and i caIeer-
counseling program inlvfor ui(ner pn\ Ideed
youth. However, a ?ro\\ inl deln-i-in
from teachers, parenti- ani local \outli
groups resulted in an e\pan,,ion (A
the program and (collalboI I tion \\~tll
other aquatic education efforts in the

Through tours, demonstrations, hands-
on activities and community events,
Fishing for Success
provides education,
recreation and
therapy to a highly
diverse group of

The response to this
program has been
phenomenal. To
date, approximately
50,000 children Dr. Cichra sparks the in



more than on demonstrations

half of the counties in Florida have
been involved in Fishing for Success.
Hundreds of school groups along
with 4H, YMCA, boys and girls clubs,
scout troops and youth camps visit
the Department in Gainesville for on-
site activities tailored to their ages and

The Fi-h-Iiii
tor Succel--
curriculpants collect specimens from
include-- lInlill\
Ipop-l1,11a e--,on-

intertebratez and
pilamnt1 \ here
participants collect specimens from
ponds with nets. They then identify the
organisms and discuss their biology,
behavior and ecological importance to
the food web of freshwater ecosystems.

also fish in
stocked ponds,
where many
have their first
with the
from the
rest of youngsters with hands- Association
for Retarded
Citizens, Eckerd Youth Alternatives and
the Meridian Behavioral Center have
benefited from this experience.

In 2002, Fishing for Success partnered
with the Alachua Regional Marine
Institute to enhance education, career
counseling and behavior modification
programs for juvenile offenders.
This partnership was extended with
a grant from the Florida Workforce
Development Board.

When groups are unable to com
to Gainesville, Fishing for Success
takes the program to them through
presentations on the morphology,
biology and ecology of fish and aquatic
invertebrates; career seminars and fairs;
and interactive exhibits at youth fairs,
museums and special events.

Fishing for Success also began hosting
monthly family fishing days in 2001 at
the Department's stocked ponds. These
evens have drawn many families. For
example, over 1,200 persons attended
an event co-hosted by the Department
and the Florida Fish and Wildlife
Conservation Commission.

In 2002, a fishing pier was built to
accommodate persons with disabilities
and special needs. The pier serves
as a staging ground for an event for
people from the Alachua County
Council for the Blind. Participants are
teamed with sighted fishing buddies,
including student volunteers from UF's
exceptional people class (College of

In addition to Drs. Canfield and Cichra,
the founders of Fishing for Success, the
program team includes Sharon Fitz-
Coy, the coordinator of educational
programs, Steve Canton, coordinators
of community events, and numerous
graduate student assistants.

In recognition of the values of this
program, the Department was named
the 2001 Florida Wildlife Federation's
Conservation Educator of the Year. Drs.
Canfield and Cichra received a USDA
Honor Award in 2003 for establishing
this innovative program, and in 2005,
Dr. Canfield was honored with the
Albert Ray Massey Citizen Volunteer
of the Year Award for his support of the
youth of Gainesville through Fishing
for Success.

Students examine a crayfish collected during a
school field trip.

Student Spotlight

started my research project in the summer of 2004
with the help of my major advisor Dr. Bill Pine
and fellow graduate student Lauren Marcinkiewicz.
My research has focused on estimating mortality
patterns in common snook, a popular sportfish in
south Florida. This project is
a cooperative effort between
the Florida Wildlife Research
Institute (FWRI) and the Center
for Fisheries Enhancement at
Mote Marine Laboratory.

Common snook are an
important game fish in south
Florida where they have been Figre 1: Surgical
heavily targeted by recreational fisheries for over 50
years. Because of this popularity and high harvest
rates, snook harvest is tightly regulated by FWRI.
Currently, there are two closed harvest seasons
(summer and winter), a 26-34" harvest window, a
two fish bag limit on the Atlantic coast, and a single
fish bag limit on the Gulf coast. In 2004, snook
were the 4th most popular sportfish on the Florida
Gulf coast.

The aim of our project is to address specific research
needs mentioned in the 2002 FWRI Snook Stock
Assessment. Estimates of fishing mortality (F) and
natural mortality (M) are key for developing effective
management plans for harvested species. Fishing
mortality has traditionally been estimated using
fisheries dependent methods (such as catch-at-age
models) and natural mortality is generally estimated
using basic life history information. FWRI funded
our project to try new methods to estimate these
vital rates. We are using acoustic tags and a series of
autonomous remote receivers to track the fates of 75
adult snook in Sarasota Bay. This approach allows
us to directly estimate F and M using an approach
with much different assumptions than the models
most often used.

During the fall of 2004, we surgically implanted
75 adult common snook with Vemco acoustic
tags (Figure 1). These tags each emit a uniquely
identifiable code and were used to track the


movements and ascertain the
fates (dead within the site, live
within the site, emigrated from
the site, not detected) of each of
the study fish. We monitored all
exits from Sarasota Bay, known snook aggregation
areas within the bay, as well as several key creeks
with stationary Vemco VR2 receivers. We also
searched the entire bay using a boat mounted
portable Vemco VR100 receiver.

j I used the data collected from
the receivers and tracking trips to
build a monthly relocation history
and assign fates to each fish.
These relocation histories were
input into the program SURVIV
to estimate monthly rates of F, M,
g implatatn and capture probability.
g implantation

As was expected F was high and peaked during
the months of the open harvest seasons. What
wasn't expected was the intense and extensive red
tide (K. Brevias) bloom that occurred in Sarasota
Bay during the summer of 2005. Following this
period, we had a large reduction in the number of
our tagged fish that were detected by our tracking
and monitoring program. Because this major
bloom coincided with a closed harvest season,
and we did not detect these fish emigrating from
the bay, we currently suspect that the observed
large change in the number of fish detected is
indicative of a large mortality event that occurred
during the most intense red tide bloom (Figure 2).
This observed rate of M for 2005 is much higher
than the mortality rate that would be estimated
using traditional life history models that are
currently used in the stock assessment.

M model 1
S 0.3 -F model 1



0.0 --
07 2 7 -o --D.
D2 0 0 0 0 C

Figure 2: F & M from Nov. 2004 through Dec.2005


SS Iauccdiety

to our recent

Alexis Caffrey
(MS, advisor Dan Canfield)

Heather Hammers
(MFAS, advisor Dan Canfield)

Emily Marecaux
(MS, advisorRuth Francis-Flod)

Mike Randall
(MFAS, advisor Tom Frazer)

Nick Trippel
(MS, advisor Mike Allen)

to Deb Murie
for her recent
promotion to
Associate Professor with
tenure in the Department
of Fisheries and Aquatic

to Craig Watson
and the other
faculty and staff
at the Tropical Aquaculture
Laboratory for ;.- ,i, r.
the 2006 annual meeting
of the Southern Extension
and Research Activities
Information Exchange

Chuck Jacoby
was invited to
attend the NOAA
National Estuarine
Eutrophication Assessment,
involving approximately
50 scientists who evaluated
current physical, chemical
and biological indicators
of oi ',alic enrichment,
eutrophication, in estuaries
around the United States.


Applications and Implications

Our current position is simple regarding the Attraction-
Production Question debated about artificial reefs it's no
longer the right question to ask. For one thing, the debate
has too often been one of mutually exclusive alternatives,
either attraction or production, and that dichotomy does
not fit our research results. Reef habitat, whether natural or
artificial, does both through understandable behavioral and
ecological processes. The question is better framed in terms
of the rates that vary with the quality of the habitat, i.e.,
movement, growth, reproduction and mortality. And mortality
rates include both natural and fishing mortality. Ironically,
the habitat characteristics most preferred by gag, presumably
to balance their need to eat and not be eaten, can also lead
to higher fishing mortality. Conservation biologists call such
situations "ecological traps". And we expect that applies
to natural as well as artificial reef habitat. The challenge is
to understand how the system functions and to manage it

The SRRS research and related extension efforts have helped
to improve the policies and practices of Florida's Artificial
Reef Program. Previously, reef builders were asked to build the
largest reefs possible with the funding and materials available.
Now, smaller reef designs are recommended to "get the
greatest bang for the reef-building buck". Previously, the State

Artificial reefs recently placed in the Steinhatchee Fisheries Management
Area to support graduate research and create a divers' trail.
would only fund artificial reefs built with scrap "materials of
opportunity," which still occurs. But now, prefabricated reef
units are commonly used, with some being commercially
produced and sold to State-funded projects. Previously,
the coordinates for every permitted artificial reef had to
be advertised for easy access by fishers. Now, if a project's
objective is fisheries conservation rather than public fishing,
such advertisement is not necessary. Previously, artificial reefs
were used almost exclusively to enhance fishing success.
Now, the State of Florida Artificial Reef Strategic Plan, adopted
by the Florida Fish and Wildlife Conservation Commission
in 2003, includes an explicit goal to use artificial reefs as a
component of fisheries and ecosystem management. And this
brings us to our research and demonstration projects now

One of the nation's largest and most
comprehensive research teams
concerned with artificial reefs is
at the University of Florida. Over
the past two decades, faculty and
students from coastal engineering,
economics, statistics, zoology and of
course fisheries and aquatic sciences
have developed a significant research
database on artificial reefs. Equally
important, there has been a concerted
effort to transfer the findings to public
and private interests developing, using
and managing artificial reefs.

Faculty from the Department of
Fisheries and Aquatic Sciences have
been prominent in fisheries and
habitat management by governmental
agencies. For example, Dr. Debra Murie
serves on the Biological Subcommittee

for Stock Assessments, Scientific and
Statistical Committee, South Atlantic
Fishery Management Council. Dr. Bill
Lindberg is a founding member of the
Florida Fish and Wildlife Conservation
Commission's Artificial Reef Advisory
Board. In these capacities, FAS faculty
contribute the best and most recent
scientific information to sustaining
marine resources for the future.

Beyond the Southeast, Dr. Bill Seaman
currently is on a European Union funded
team to organize the world's first short
course on Design and Management
of Artificial Reefs for Fisheries, to be
offered to natural resource professionals
in 2007. Seaman's book, "Artificial
Reef Evaluation," is used worldwide by
scientists to quantify the performance
of reefs.

FAS faculty also provide technical
backstopping to the outreach efforts
of the Florida Sea Grant Extension

Program, which works with local
stakeholders on a variety of applied
coastal issues such as waterways
management, environmental quality,
seafood technology and hurricane
preparedness. In the case of artificial
reefs, local Extension agents may assist
development of artificial sites or offer
workshops that educate the public as
well as reef coordinators on scientific

As artificial reefs are applied to a
growing number of situations beyond
the traditional enhancement of fisheries,
such as habitat restoration, eco-tourism
and marine ranching, FAS faculty will
regularly devote effort to helping those
applications use the best available
scientific information, whether it
comes from Florida's research program
or from ecosystems across the globe.

Bill Seaman

Results from the SRRS indicate that juvenile gag could
experience a bottleneck in their transition from inshore nursery
grounds to offshore spawning stock, since natural habitat that
favors both growth and survival is apparently sparse on the
shallow shelf. A new Steinhatchee Fisheries Management Area
(SFMA) will test that hypothesis and, if confirmed, demonstrate
how designed artificial reef systems might function as fisheries
management tools. Eventually almost 100 square miles
will be enhanced with up to 1000 small, widely scattered
conservation reefs. To judge gag output from the SFMA, a
line of standardized reefs have already been built offshore,
bracketing the Big Bend for fisheries independent monitoring.
Our federally funded work is also using advanced technologies
to help measure the quality of natural hard-bottom habitat
(EFH) of the region. Reef Ballsfor an underwater nature trail,
were recently deployed in the southern SFMA, and the State is
fundingTaylor County to develop 5 square miles of the SFMA,
zoned for low densities of larger reefs, to enhance fishing. The
purpose is to advance science, fisheries conservation, and
rural economic development in a compatible fashion.

The science being done also has practical importance well
beyond the advance of artificial reef technology. For example,
current stock assessments for gag and other reef fish lack
adequate fisheries independent indices for fine-tuning the
assessment models. Together, the ecological theories we're
applying to gag, our spatial measures of EFH and our sampling

of standardized reef units lead us to expect improved fisheries
independent indices in the future. Similarly, state, federal and
University fisheries scientists have been working together to
advance spatially explicit multi-species fisheries models, with
Florida's grouper as a test case. Out of necessity (i.e., data
and computing constraints), such models operate at much
coarser spatial scales than the habitat selection and ecological
processes thought to underlie population dynamics. Our
research is critically examining key assumptions required for
such complex modeling, and as such reinforces this evolving
fisheries modeling approach.

In Florida, the fishing public is very aware that high quality
habitat is vitally important to the Nation's most valuable
and diverse fisheries. So, too, are the many researchers and
extension educators cooperating to advance the science and
technologies required to meet the growing challenges of 21st
Century fisheries management.
References Cited:
Kiel, B. L. 2004. Homing and spatial use of gag grouper, Mycteroperca
microlepis. Master's Thesis. University of Florida, Gainesville, FL. 79 pp.
Larsen, S. J. 2005. Influence of high-resolution spatial information on
resource exploitation: an example from angler impacts on artificial reefs.
Master's Thesis. University of Florida, Gainesville, FL. 45 pp.
Lindberg, W.J., T.K. Frazer, K.M. Portier, F Vose, J. Loftin, D.J. Murie, D.M.
Mason, B. Nagy, M.K. Hart. 2006. Density-dependent habitat selection
and performance by a large mobile reef fish. Ecological Applications

Lake Okeechobee Florida's largest lake has a surface area near 1,800 km2 and it
is one of the largest lakes in the USA. The lake is extremely shallow, with a mean
depth of 3m, and as a result, it is highly influenced by wind (frontal systems,
tropical storms, and hurricanes), which stirs up mud sediments from the lake
bottom and often results in highly turbid water. Shoreline areas of the lake can
support diverse communities of aquatic plants, and these in turn provide good
habitat for sport fish. The lake is particularly well known for its largemouth bass
and black crappie fisheries. The status of these fisheries has waxed and waned in
recent years due to periods of habitat loss that are linked with high water and
hurricane impacts. Hurricanes View of the lake from the west, looking out over a large
Frances and Jeanne impacted the marsh zone to the open water area.
-7 lake in summer 2004, destroying most of the shoreline aquatic vegetation, which has yet
to recover. Coincident with this habitat loss, fisheries managers have documented a
substantial decline in recruitment of young bass into the population. A prolonged period
of low water will be necessary to recover the essential fish habitat in Lake Okeechobee.
Management of the resource is a joint effort of the South Florida Water Management
District, the US Army Corps of Engineers, and the Florida Fish and Wildlife Conservation
Commission. Research conducted by faculty in the UF/IFAS Department of Fisheries and
Aquatic Sciences has substantially contributed to the existing knowledge about how
nutrients, water levels and other factors control the dynamics of this large lake and several
Uprooted vegetation along the western lake shore of our graduates have conducted their thesis or dissertation research on the lake.
after the 2004 hurricanes.
WaterWorks is produced by the UF/IFAS Dept. of Fisheries & Aquatic Sciences. Dr. Karl Havens, Chair khavens@ufl.edu

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