Theses and Dissertations

Defense Date

12-1998

Document Type

Dissertation

Degree Name

Ph.D. Oceanography/Marine Biology

Department

Oceanographic Center

First Advisor

Bart J. Baca

Second Advisor

Curtis M. Burney

Third Advisor

Richard E. Dodge

Fourth Advisor

George E. Krantz

Fifth Advisor

Richard E. Spieler

Abstract

Florida pompano (Trachinotus carolinus) are highly prized food and sport fish indigenous to coastal areas of the southeastern United States. A commercially valuable fishery has historically existed in the Gulf of Mexico and on the South Atlantic seaboard. Efforts to economically culture Florida pompano in a captive environment were only partially successful. Four experiments were performed to explore the physical and environmental requirements of Florida pompano and other closely related species in the Family (Carangidae):

Experiment #1- Semi-natural spawning was induced with newly developed hormonal implants. to initiate and sustain semi-natural spawning in captive Florida pompano. Fish collected from the wild were induced to spawn naturally using the hormone luteinizing hormone-releasing hormone. Sexually mature male and female fish received ethylene-vinyl acetate copolymer (EVAC) implants containing either 25 µg/Kg LHRH-a (experimental), or placebo implants containing no LHRH-a (control). Spawning and natural fertilization commenced 1 d post implantation and continued through 9 d. A total of 202,700 eggs were collected. Overall mean fertilization success in the experimental groups was 44%. No spawning occurred in the control groups. Hatching success of all fertilized eggs was > 90%. Results indicate that effective spawning and natural fertilization can be initiated and maintained with continuous release LHRH-a implants.

Experiment #2 - Different growout environments, compared the growth of juvenile Florida pompano cultured in three captive growout environments over a 95 day growout period. One of the experimental growout environments was a tall (height/diameter) polyethylene tank that had an upwelling current. Five (N=5) fish 19.0±0.65g were grown in each of the upwelling tanks (5 replicates). A second group of pompano were grown in net cages. Five (N=5) fish 20.8±0.56 g were grown in each of the circular net cages (5 replicates). A third treatment, standard circular, tangential-flow tanks (1,776 L)( 4 replicates), were stocked with (N=12) juvenile pompano 19.3±0.41g. Weekly sampling was done to assess any change in weight, and to facilitate tank and cage cleaning. A pelletized feed specifically formulated for Florida pompano was supplied to all fish at a 10% body mass/day ration.

Juvenile Florida pompano in the upwelling environment displayed significantly greater growth (P

Experiment #3 - An experimental diet specifically formulated for Florida pompano was compared to a standard pelletized trout chow (Purina). An experimental diet treatment was supplied to twelve (N=12) fish that weighed 19.3±0.41g (4 replicates), and were stocked into 1,776 L circular, tangential-flow tanks. The control treatment receiving trout chow (N=12) weighed 19.6±0.68g (4 replicates), were stocked into identically configured tanks. All groups were fed at a 10% body mass/day ration of either trout chow or experimental diet. The experimental period was 59 days.

The groups of juvenile Florida pompano that received the experimental diet exhibited significantly better growth (P

Experiment #4 - Two modes of feed application were tested on juvenile Florida pompano. An experimental group (N=10) 158±6.4g (4 replicates), were allowed to feed themselves by use of a demand feeder. A control treatment (N=10) 159±2.9g (4 replicates) were supplied with an equally divided daily feed ration at two preset times during the day to simulate hand feeding. Food application in the control group was made by a vibratory feeder. All groups were fed at a 6% body mass/day ration with Purina® Trout Chow. The Florida pompano were grown out in identical 1,776 L circular, tangential-flow tanks.

After 79 days in culture, the experimental groups exhibited no significant difference in weight over the control groups (P>0.05). Several reoccurring problems were instrumental in changing food delivery pattems in the tanks with the demand feeding regime. Typically, the ten fish in the demand feeding tanks would repeatedly strike the demand bar (day or night) until all of the daily ration had been dispensed. Other problems including environmental interference (wind and rain activating the demand feeders), and mechanical failure (freshwater feeders in a marine environment) effected the demand feeders operation. Demand feeding may be an alternate feeding method for Florida pompano if environmental control is available, modifications can be made to improve the feeders in a marine environment, and the pool of fish being fed is sufficiently large enough to absorb almost continual feed application at the maximum rate of delivery possible from this type of feeder.

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