• TABLE OF CONTENTS
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 Front Cover
 Title Page
 Introduction
 Methods and materials
 Results
 Discussion
 Discussion
 Conclusions
 Literature cited






Group Title: Technical paper / Florida Sea Grant College Program ; no. 38
Title: Survival and growth of cut vs hooked commercial sponges in the Florida Keys
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 Material Information
Title: Survival and growth of cut vs hooked commercial sponges in the Florida Keys
Series Title: Technical paper Florida Sea Grant College
Physical Description: 12 p. : ill. ; 28 cm.
Language: English
Creator: Stevely, John
Sweat, Don
Florida Sea Grant College
Publisher: Sea Grant Extension Program
Place of Publication: Gainesville Fla
Publication Date: 1985
 Subjects
Subject: Sponges -- Florida   ( lcsh )
Sponges -- Growth -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Bibliography: p. 12.
Statement of Responsibility: by John Stevely and Don Sweat.
General Note: Grant NA80AA-D-00038.
Funding: This collection includes items related to Florida’s environments, ecosystems, and species. It includes the subcollections of Florida Cooperative Fish and Wildlife Research Unit project documents, the Florida Sea Grant technical series, the Florida Geological Survey series, the Howard T. Odum Center for Wetland technical reports, and other entities devoted to the study and preservation of Florida's natural resources.
 Record Information
Bibliographic ID: UF00075989
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: oclc - 17445408

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Table of Contents
    Front Cover
        Front Cover
    Title Page
        Title Page
    Introduction
        Page 1
        Page 2
    Methods and materials
        Page 2
        Page 3
        Page 4
    Results
        Page 5
        Page 4
    Discussion
        Page 6
    Discussion
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
    Conclusions
        Page 11
    Literature cited
        Page 12
Full Text
Technical Paper No. 38


HUME LIBRARY
APR 11 1o
LF.A.S.- Univ. of Florird


Cut vs


Survival
Hooked
in the


and Growth
Commercial
Florida Keys


of
Sponges


by
John Stevely
and
Don Sweat


FLORIDA SEA GRANT COLLEGE


OR










SURVIVAL AND GROWTH OF CUT
VS.
HOOKED COMMERCIAL SPONGES IN THE FLORIDA KEYS






John Stevely and Don Sweat



Florida Sea Grant Extension Program
117 Newins-Ziegler Hall
University of Florida
Gainesville, FL 32611






Project No. IR-82-15
Grant No. NA80AA-D-00038





Technical Papers are duplicated in limited quantities for specialized
audiences requiring rapid access to information. They are published with
limited editing and without formal review by the Florida Sea Grant College
Program. Content is the sole responsibility of the author. This paper was
developed by the Florida Sea Grant College Program with support from NOAA
Office of Sea Grant, U.S. Department of Cmnnerce, grant number
NA80AA-D-00038. It was published by the Sea Grant Extension Program which
functions as a component of the Florida Cooperative Extension Service, John
T. Woeste, Dean, in conducting Cooperative Extension work in Agriculture,
Home Economics, and marine Sciences, State of Florida, U.S. Department of
Commerce, and Boards of County Commissioners, cooperating. Printed and
distributed in furtherance of the Acts of Congress of May 8 and June 14,
1914. The Florida Sea Grant College is an Equal Employment-Affirmative
Action employer authorized to provide research, educational information and
other services only to individuals and institutions that function without
regard to race, color, sex, or national origin.


TECHNICAL PAPER NO. 38
September 1985









INTRODUCTION


Until the 1940's, the sponge fishery was one of the most valuable

fisheries in Florida. However, a combination of the sponge blights of 1939

and 1946 and the introduction of synthetic sponges resulted in reduction of

the fishery to a small fraction of its former importance (Stevely, et al.,

1978). In recent years, increasing scarcity of sponges in the sponge beds off

of Tarpon Springs has threatened the continued existence of the remaining

Tarpon Springs sponge fleet.

Although an exploratory sponge fishing survey of state territorial waters

off of Monroe County (Florida Keys), Florida, had indicated that commercial

quantities of sponges were present (Sweat and Stevely, unpublished man-

uscript), Florida Statute (F.S. 370.17) prohibits use of "deep sea diving

apparatus to harvest sponges in this area." This Statute states, "No person

may use diving suits, helmets, or other apparatus used by deep sea divers in

taking commercial sponges from any waters within the territorial limits of

this state."

The purpose of the law was not to prohibit reasonable methods of

harvesting sponges but to protect young sponges. It was enacted to prevent

damage to young sponges caused by heavily weighted divers stepping on them.

Early sponge diving gear was of the deep sea variety. Scuba and hookah,

common gear today, did not become a viable method of extended underwater

diving until many years after enactment of the law. Light hookah gear with

rubber-soled, canvas athletic shoes has now replaced the heavy helmet and lead

boot-clad diver.

The Florida Saltwater Fisheries Study and Advisory Committee recommended

in 1982 that sponge diving be allowed in the state territorial waters off








Monroe County. However, objections were raised concerning the possibility of

overfishing due to increased fishing pressure following legalization of sponge

diving. Therefore, the present project was undertaken for the purpose of

establishing whether a change in harvesting technique -- cutting rather than

tearing the sponge loose -- could insure sponge regeneration and thus reduce

the possibility of overfishing. Sponges have remarkable regenerative ability;

and if even a small quantity of sponge material is left attached to the

substrate, the sponge may survive and grow back to a commercially valuable

size.


METHODS AND MATERIALS


During June, 1982, a commercial sponge fisherman assisted the project

by locating a bed of sheepswool sponges (Hippiospongia lachne) off of Vaca Key

(Marathon) in the Florida keys (Fig. 1). The site was marked with a buoy, and

Loran C coordinates were recorded to insure relocation of the study site. The

bottom of the site was marked off by laying out a grid of polyethylene line

held in.place-by rebar stakes driven into the substrate. Sponges were located

by swimming along the grid lines. Upon locating a sponge, its position was

marked by attaching a piece of brightly colored surveyor's flagging tape to

the line. The position was also recorded on a plastic chart of the grid

pattern. Large calipers (S & S standard radiological) were used to take two

measurements of the sponge's diameter and one measurement of the sponge's

height.

After being measured, alternate sponges were either cut loose using

a large, sharp knife or torn loose with a sponge hook on the end of a three-

foot handle. Sponges were cut as close to the substrate as possible while

attempting to leave a complete sponge base. In practice, this left 1/2 to 1








Monroe County. However, objections were raised concerning the possibility of

overfishing due to increased fishing pressure following legalization of sponge

diving. Therefore, the present project was undertaken for the purpose of

establishing whether a change in harvesting technique -- cutting rather than

tearing the sponge loose -- could insure sponge regeneration and thus reduce

the possibility of overfishing. Sponges have remarkable regenerative ability;

and if even a small quantity of sponge material is left attached to the

substrate, the sponge may survive and grow back to a commercially valuable

size.


METHODS AND MATERIALS


During June, 1982, a commercial sponge fisherman assisted the project

by locating a bed of sheepswool sponges (Hippiospongia lachne) off of Vaca Key

(Marathon) in the Florida keys (Fig. 1). The site was marked with a buoy, and

Loran C coordinates were recorded to insure relocation of the study site. The

bottom of the site was marked off by laying out a grid of polyethylene line

held in.place-by rebar stakes driven into the substrate. Sponges were located

by swimming along the grid lines. Upon locating a sponge, its position was

marked by attaching a piece of brightly colored surveyor's flagging tape to

the line. The position was also recorded on a plastic chart of the grid

pattern. Large calipers (S & S standard radiological) were used to take two

measurements of the sponge's diameter and one measurement of the sponge's

height.

After being measured, alternate sponges were either cut loose using

a large, sharp knife or torn loose with a sponge hook on the end of a three-

foot handle. Sponges were cut as close to the substrate as possible while

attempting to leave a complete sponge base. In practice, this left 1/2 to 1









inch of sponge tissue. The sponge hook was of the type used by commercial

sponge divers. When the sponge was removed, the type of harvesting method
used was recorded and measurements taken of the remaining sponge base (if

there was any left). The exact location of each sponge was marked by driving


Figure 1.


0, c, \


Sponge
\ Sites 7
Study Area

,, 1. 9 / *7
/ 'r /4
\ Ir SM 3 7




9** 9 B.r
6. .
a1 61 S" Kw...t
0 6 5 2 2 2









8 2





.- s\ S> 29 S 22 \ .
WSJ a 38 2 C.





"ia^ "^!^^3_^^ l ^/C-1^ ,^7^^ .6 ^ 3^ *>3^ 0>










a rebar stake into the substrate. A numbered, plastic bird band was wrapped

around these stakes for identification. Also, in those cases where sponge

base was left behind, the sponge base was marked by "sewing" a piece of

monofilament line through it and then attaching a plastic bird band. Ten

sponges were staked and tagged to serve as a control group. Growth and

survival data for experimental and control sponges were collected 12 months

(May '83) and 28 months (Nov. '84) after the study was begun.


RESULTS


Survival of Cut and Hooked Sponges

A total of 69 sponges were either cut (N=35) or hooked (N=34).

Approximately one-third of all the study sponges (control, cut, hooked) were

not found by the end of the experiment for a variety of reasons which are

discussed (Fig. 2). The percentages of found sponges for each group of

sponges were not significantly different (G-test; Sokal and Rohlf, 1969).

Twelve months after the study began, 70% of the found cut sponges were

alive and 39% of the found hooked sponges were alive (Fig.3). The percentage

of surviving cut sponges compared to that of surviving hooked sponges was

significantly different (G-test; P<.05).

Twenty-eight months after the study began, 71% of the found cut sponges

were alive and 41% of the found hooked sponges were alive (Fig. 3). Again,

the proportion of surviving sponges between the treatments was significantly

different (G-test; P<.05).

The slightly higher percentage of surviving cut and hooked sponges

found at 28 months compared to 12 months was not significantly different and

can be attributed to sampling error. Since fewer sponge sites were found at

28 months (Fig. 2.), the sample size used to calculate percentages of








surviving sponges was smaller (number of found cut and hooked sponge sites

was 55 at 12 months and 47 at 28 months).

On both sampling dates, 100% of the found control sponges were alive.

The percentage of surviving found control sponges was significantly different

from the percentage of surviving found cut and hooked sponges (G-test; P<.05).

Growth of Experimental and Control Sponges

Average increase of the maximum diameter of the cut sponge bas was 2.3

cm. (range: -1.5 to 5.0 cm.) after 28 months. Average increase of the maximum

diameter of the hooked sponge base was 2.1 cm. (range 0.0 to 4.00).

Only a small number of surviving cut sponges (7, or 39%) and hooked

sponges (3, or 33%) were judged to have regrown to a commercial size. Whether

sponges had or had not grown to a commercially harvestable size was a qual-

itative judgement. Although most of the surviving sponge bases had grown to

the point of exceeding 12.7 cm. (to be legal size a sponge must have, when

wet, a maximum diameter of at least 12.7 cm), they had not yet grown in height

sufficiently enough to be judged as a truly commercially valuable product by

the authors. Therefore, only sponges which could be crudely estimated to have

attained a height of at least 7.6 cm. were considered as commercial-sized

sponges. However, there is no legal requirement for a minimum sponge height.

The average natural growth rate of control sponges monitored during the

study (7 of the 10 original controls were found at the end of the study) was

1.7 cm./year.










a rebar stake into the substrate. A numbered, plastic bird band was wrapped

around these stakes for identification. Also, in those cases where sponge

base was left behind, the sponge base was marked by "sewing" a piece of

monofilament line through it and then attaching a plastic bird band. Ten

sponges were staked and tagged to serve as a control group. Growth and

survival data for experimental and control sponges were collected 12 months

(May '83) and 28 months (Nov. '84) after the study was begun.


RESULTS


Survival of Cut and Hooked Sponges

A total of 69 sponges were either cut (N=35) or hooked (N=34).

Approximately one-third of all the study sponges (control, cut, hooked) were

not found by the end of the experiment for a variety of reasons which are

discussed (Fig. 2). The percentages of found sponges for each group of

sponges were not significantly different (G-test; Sokal and Rohlf, 1969).

Twelve months after the study began, 70% of the found cut sponges were

alive and 39% of the found hooked sponges were alive (Fig.3). The percentage

of surviving cut sponges compared to that of surviving hooked sponges was

significantly different (G-test; P<.05).

Twenty-eight months after the study began, 71% of the found cut sponges

were alive and 41% of the found hooked sponges were alive (Fig. 3). Again,

the proportion of surviving sponges between the treatments was significantly

different (G-test; P<.05).

The slightly higher percentage of surviving cut and hooked sponges

found at 28 months compared to 12 months was not significantly different and

can be attributed to sampling error. Since fewer sponge sites were found at

28 months (Fig. 2.), the sample size used to calculate percentages of









DISCUSSION


Survival of Cut and Hooked Sponges

This study shows that both cut and hooked sponges can successfully regrow

to a commercially harvestable size. However, cut sponges have a substantially

higher chance for survival and consequently have a higher chance for regrowth

to a commercial size than do hooked sponges. The higher survival rate of cut

sponges can be attributed to the fact that cutting insures that some sponge

tissue is left attached to the substrate. Sponge tissue is sometimes left

behind when hooking the sponge; but often when the sponge is torn free, very

little tissue is left. If sufficient sponge tissue is not left, sediment can

easily smother the remaining sponge tissue.

It is probable that higher survival of cut sponges than that recorded in

this study could be realized if the sponges were cut so that a taller sponge

base was left behind, reducing the chances of the sponge being smothered by

sediment. However, this is economically impractical for a commercial sponger

at the present time since leaving an additional 3 to 5 cm. of sponge tissue

would substantially reduce the value of the harvested sponge. On the other

hand, the base of most sponges is embedded with rock and foreign material and

normally is trimmed and discarded before retail sale, so an educational,

voluntary program directed at sponge producers and buyers might be helpful.

Any management technique based on the requirement to leave a minimum height

would be unenforceable since it is impossible to determine at what level a

harvested sponge was cut.

If it is assumed that all "lost" sponges represent mortality due

to experimental treatment (cutting or hooking) then the survival of all

experimental sponges would be lower than that observed for only sponges (or








Figure 2.

Percentage of sponge sites found, (number of
sponge sites found/total number of sponge sites)
x 100, May 1983 and Nov. 1984.


100%-

90%-

80%-

70%-
60%-
50%-

40%-

30%-

20%-


10%-


MAY
1983


Rfln


70%


ITT


CONTROL
N-10


NOV.
1984
82%


77%


71%
1T]


65%


HOOKED
N-34


---~-









Figure 3.

Percentage of sponges found which survived,
(number living sponges/number sponge sites
found) x 100, May 1983 and Nov. 1984.



100% 100%100% Eli
M10 MAY NOV.
90%1983 1984
90%-

| 80%-
0 70% 71%
q 70%-

S60%-

50%
0 40 '41%
0 40%-


S 20%

10%-

CONTROL CUT HOOKED
N-10 N-35 N-34








the stakes marking their positions) which were found. Complete mortality

of "lost" sponges was not deemed likely by the authors for the following

reasons: 1) a similar portion (30%) of the control sponges were "lost"

compared to the experimental sponges; 2) the sponges were widely scattered

over a large area; and with the limitations of underwater visibility, it was

impossible to locate all sponges; 3) at times the area was heavily fished by

lobster trap fishermen and a number of marker stakes could have been

inadvertently dislodged by traps.

Therefore, a maximum estimate of survival would be 71% for cut sponges

and 41% for hooked sponges based on data on found experimental sponge sites

(N=47). A minimum estimate of survival would be 51% for cut sponges and 26%

for hooked sponges based on number of sponges in the initial experimental

group (N=69).

Growth of Experimental and Control Sponges

The results of this study demonstrate that at least 2 years are required

for the surviving sponge base to regrow to a minimum commercial size. The

observed growth rate would indicate that 1 or 2 additional years would be

desirable to insure that a higher percentage of sponges attained harvestable

size. The additional time would also allow the sponges to grow to a larger

and thus more valuable size.
Historically, several studies of sheepswool sponge growth (Moore,

1910; Crawshay, 1939; Storr, 1964) have measured sponge growth in terms of

volumetric increases (the number of times a sponge increases in volume during

a 1-year period). Variability in sponge shape and repeated attempts to obtain

reproducible measurements of sponge height were such that volumetric estimates

of sponge size were judged to be inappropriate. Therefore, in this study,









sponge growth was expressed in terms of increase in the maximum sponge

diameter. Based on repeated measurements of several sponges conducted at the

study's beginning, the maximum sponge diameter was the only measurement found

to be reproducible within 0.5 cm. These observations have been confirmed in

a recent study of sponge growth in Biscayne Bay, Florida (pers. comm., J.

Tilmant; Everglades National Park, Homestead, FL).

Although direct comparison is difficult, growth of control sponges

in this study appears to be somewhat slower than that recorded in older

studies. Storr (1964) measured a growth factor of 2.27 (number of times a

sponge increases in volume during a 1-year period) for sheepswool sponges

from Piney Point, Florida. Based on this growth rate, Storr estimated it

would require at least 3 years to reach a harvestable size. Moore (1910)

studied sheepswool sponge growth at Anclote Key and Sugarloaf Key, Florida,

and measured growth factors lower than Storr's data (1.91 and 1.86 respec-

tively). Smith (1973) studied a different species of commercial sponge, the

grass sponge (Spongia graminea), in Card Sound, Florida, and reported a growth

factor of 0.77. Studies of sheepswool sponges in the Bahamas and British

Honduras (Crawshay, 1939) found growth rates of 2.34 to 2.94.

Tilmant (pers. comm.) working on sheepswool sponge growth rate in

Biscayne Bay, Florida, reported a 2.0 cm./year increase in diameter. This

growth rate would produce a commercial sponge in approximately 6.4 years. The

growth rate measured in this study of 1.7 cm./year would produce a commercial

sponge in 7.5 years.

The variability of sheepswool sponge growth rates from different

locations is noted in the literature (Stevely, et al., 1978). Substantial

differences in growth rates of commercial grass sponges (Spongia graminea)









located on the same rock outcropping have been reported (Smith, 1973). It

is possible that this study was located in an area not conducive for rapid

sponge growth. However, sponges in the area were abundant and appeared to

be in healthy condition. Sponge fishermen were seen working the general area,

although most sponging activity was conducted closer to Vaca Key in shallower

water. Therefore, it seems reasonable to assume that the study site was

representative of commercially productive sponge bottom.


CONCLUSIONS


1. Sponge tissue left attached to the substrate after the sponge has been

harvested by either cutting or hooking can survive and grow.

2. Survival of remaining sponge tissue is substantially greater when sponges

are harvested by cutting compared to those sponges harvested by hooking, since

cutting insured that more regenerative sponge tissue was left attached to the

substrate.

3. The maximum estimate of sponge survival for cut sponges is 71% and

for hooked sponges is 41%. The minimum estimate of sponge survival for cut

sponges is 51% and for hooked sponges is 26%.

4. At least 2 years is required for surviving sponge tissue to regrow to

a commercially harvestable size. An additional 1 or 2 years is required for

more sponges to attain a more valuable size.

5. Any attempted management of the sponge fishery requiring, by statute,

a minimum height requirement to be left when cutting a sponge would be

unenforceable, and that this "recommendation" could be better addressed by

an educational program directed at both sponge producers and buyers.









located on the same rock outcropping have been reported (Smith, 1973). It

is possible that this study was located in an area not conducive for rapid

sponge growth. However, sponges in the area were abundant and appeared to

be in healthy condition. Sponge fishermen were seen working the general area,

although most sponging activity was conducted closer to Vaca Key in shallower

water. Therefore, it seems reasonable to assume that the study site was

representative of commercially productive sponge bottom.


CONCLUSIONS


1. Sponge tissue left attached to the substrate after the sponge has been

harvested by either cutting or hooking can survive and grow.

2. Survival of remaining sponge tissue is substantially greater when sponges

are harvested by cutting compared to those sponges harvested by hooking, since

cutting insured that more regenerative sponge tissue was left attached to the

substrate.

3. The maximum estimate of sponge survival for cut sponges is 71% and

for hooked sponges is 41%. The minimum estimate of sponge survival for cut

sponges is 51% and for hooked sponges is 26%.

4. At least 2 years is required for surviving sponge tissue to regrow to

a commercially harvestable size. An additional 1 or 2 years is required for

more sponges to attain a more valuable size.

5. Any attempted management of the sponge fishery requiring, by statute,

a minimum height requirement to be left when cutting a sponge would be

unenforceable, and that this "recommendation" could be better addressed by

an educational program directed at both sponge producers and buyers.








LITERATURE CITED


CRAWSHAY, L. R., 1939. Studies in the market sponges. 1. Growth from the
planted cutting. Jour. Mar. Biol. Assn. of the U.K. 23:553-574.

MOORE, H. F., 1910. The commercial sponges and the sponge fisheries. Bull.
U.S. Bur. Fish., Vol. 28, Part 1, 1908:399-511.

SOKAL, R. R., and F. J. ROHLF, 1969. Biometry: The principles and
practice of statistics in biological research. W. H. Freeman and Company,
San Francisco. 776 pp.

SMITH, R. L., 1973. Abundance and diversity of sponges and growth rates of
Spongia graminea in Card Sound, Florida. Master's Thesis, Univ. Miami, Coral
Gables, Florida. 66 pp.

STEVELY, J. M., J. C. THOMPSON and R. E. WARNER, 1978. The biology and
utilization of Florida's commerical sponges. Florida Sea Grant College
Program Tech. Rept. No. 8. 45 pp.

STORR, J. F. 1964. Ecology of the Gulf of Mexico commercial sponges and its
relation to the fishery. U.S. Dept. Interior, Fish. Wild. Serv., Spec. Sci.
Rept. No. 4666:1-73.




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