Date of Award

Spring 5-2007

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Chair

Jeffrey Lotz

Committee Chair Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 2

Jason Lemus

Committee Member 2 Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 3

Reginald Blaylock

Committee Member 3 Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 4

Bruce Comyns

Committee Member 4 Department

Coastal Sciences, Gulf Coast Research Laboratory

Abstract

Historically, red snapper (Lutjanus campechanus) larviculture at the Gulf Coast Research Lab (GCRL) used 25 ppt artificial salt water and mixed, wild zooplankton composed primarily of Acartia tonsa, a calanoid copepod. Acartia tonsa was collected from the estuarine waters of Davis Bayou and bloomed in outdoor tanks from which it was harvested and fed to red snapper larvae. We are developing a more controlled copepod mass culture system to support finfish larviculture. To that end, I examined the effect of single species versus mixed species of algae as food for the copepods. Wild A. tonsa were isolated and reared in a controlled environment. Diets used for culture of A. tonsa were T- Iso (Tahitian strain Isochrysis galbana) and Chaetoceros (Chaetoceros mulleri). Mated female copepods (n=lOO) were isolated from the laboratory population and placed individually in 10-ml containers. Twenty-five were fed T-Iso only at a cell density of300,000 cells/ml, 25 were fed C. mulleri only at a cell density of 300,000 cells/ml, and 25 were fed a mixture of both T-Iso and C. mulleri at a cell density of 150,000 cells/ml each and 25 were fed no algae. Eggs were collected and counted to quantify fecundity over a 72-hour period. The experiment was repeated. Fecundity was higher in the mixed diet treatment where 17 of the 25 female A. tons a survived ( 68% survival) and produced a total of 520 eggs.

Fecundity of A. tonsa in the small-scale experiment fell within the published range of20-150 eggs/female/day for all the treatments offered a diet. Egg production in treatments receiving a mixed diet was higher than production from any of the single diet fed treatments in all small-scale experiments. Production in the unfed treatment was significantly lower (p<0.05) than in all small-scale experiments. Diet did not affect survival (p>0.05) in any fed or unfed treatments over the 72-hour duration of the experiments. In a larger scale experiment, a total of 20, !-liter beakers involving 5 replicates per treatment were used. Copepod density, algal density, water temperature, and salinity were the same as in the small-scale experiments. This larger scale experiment also was replicated. Individual egg production for the larger scale system fell within the published range of20-150 eggs/female/day for the algal fed treatments. Individual production in the unfed control was below 3 eggs/female/day. The hatch rate of eggs produced from a larger scale experiment was not significantly different between treatments indicating that diet had no effect on the hatch rate and that eggs produced from the experiment were fertile.

Overall, the copepods produced eggs at a rate comparable to both published results and previous experiments at GCRL in all the algal fed treatments while few eggs were produced in the unfed controls. However, egg production was more consistent in the mixed diet than in the single species diet both when the copepods were tested singly and in a larger scale. There was no effect of diet on survival within each experiment when the copepods were tested singly and no effect of time on egg production. Between experiment, variability may be attributed to variability in algal quality, specifically in single diet treatments.

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