Date of Award

5-2006

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Marine Bio-Resources

Advisor

Linda J. Kling

Second Committee Member

Nick P. Brown

Third Committee Member

Mary S. Tyler

Abstract

Atlantic halibut, Hippoglossus hippoglossus, has emerged within the last decade as an aquaculture species for the food fish industry, primarily due to an enduring high market value and the species potential for domestication. The halibut farming industry is relatively small scale with research efforts focused on larval production. The current project examined the effect of diet on the reproductive performance of wild captive broodstock. Broodstock diet has been shown to influence egg quality, i.e. fertilization rates, hatch rates, and the survival of yolk-sac larvae to first feeding by altering the nutrient content of eggs, specifically the fatty acids composition. The diet most often used in the industry consists of fresh fish. However, this diet can introduce pathogens to the broodstock and larvae. This study compares two bio-secure formulated diets and a control diet made up of fresh fish and squid. The two formulated diets selected were a commercial diet produced by INVE, and an experimental diet (CCAR). Thirty-eight wild caught halibut were acclimated to captivity for two to three years prior to the experiment with a diet of fresh fish. At the start of the experiment in September 2003, the broodstock were randomly divided into nine tanks and each treatment was assigned randomly to three tanks. The halibut from two treatments were weaned onto formulated diets in January of 2004 and diets were fed over the course of the year. Egg quality was observed for 2004 and 2005 spawning seasons. The 2005 spawning season detected no differences among treatments in egg quality. However, diet did affect the levels, by percent of total lipid and by total mass, of two essential fatty acids in the eggs i.e. arachidonic acid (ArA), and eicosapentaenoic acid (EPA). The spawning performance all of the treatments, including the control, was extremely poor compared to other published reports. Only one female in the control treatment had both fertilization and hatch rates greater than 50% in 2004 and 2005. The best explanation for this is the broodstock were still adapting to the stress of being in captivity and possible additional stress such as temperature and salinity variation, and onsite construction. Stepwise multiple regressions was used to further understand any relationship between egg quality, i.e. fertilization rates and hatch rates, and egg fatty acid content in 2004 and 2005 spawning seasons. An principle component analysis grouped fatty acid variables into independent variables before being entered into the regression. An analysis of covariance (ACOVA) with females was used to identify any relationships among these variables and the egg with egg quality. The ANCOVA showed fertilization rates were related to egg source and the levels of essential fatty acids in 2004, while fertilization rates were related to egg source and two unidentified fatty acids in 2005. Also, hatch rates were related with fertilization rates in 2004, while a relationship to hatch rate was not identified in 2005. It is concluded that poor spawning rhythms and egg quality may have masked any possible effect of diet on egg quality for this study.

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