INNOVATIVE BIOTECHNOLOGIES FOR ENVIRONMENTALLY SUSTAINABLE AND ECONOMICALLY COMPETITIVE AQUACULTURE ACROSS NORTH CAROLINA

Our studies will address several key issues in farming of hybrid striped bass (HSB) including problems with striped bass egg quality, suboptimal growth of farmed HSB induced by various stressors, the need for bio-engineering and economic data on production of HSB in a recirculating aquaculture system (RAS), and the ability to dispose of effluents from outdoor HSB ponds via land application. We will determine whether the major system for uptake of yolk proteins by growing oocytes is disrupted in striped bass producing low quality eggs. This system involves three receptors for circulating yolk precursors, vitellogenins, that are expressed on the oocyte surface. The genes encoding these receptors will be cloned and characterized and receptor gene expression will be measured in ovarian biopsies taken from females producing good and poor quality eggs. The extent to which, and mechanisms whereby, stress adversely effects the growth of farmed HSB are presently unknown and will be investigated. Fish in various states of growth induced by different feeding regimens will be sampled for blood and liver tissue. Levels of the major stress hormone, cortisol, will be measured in the blood plasma and liver cortisol receptor abundance and function and receptor gene expression will be evaluated. Fish growth, feed conversion and other metabolic parameters will be assessed. Results will indicate the degree to which growth status is associated with hormone (cortisol) levels and signaling. Reliable engineering and economic information on commercial production of HSB in RAS facilities is unavailable and will be generated in this project in research conducted at the N.C. State University Fish Barn. The RAS will be upgraded by addition of new biofilters and more energy efficient water and air heat pumps and the systems will be stocked with HSB fingerlings, which will be grown to market size using standard diet and feeding practices. Growth and standing biomass of the fish and feed conversion rates will be monitored as will standard water quality parameters and the operational characteristics of the water filtration and heating systems. Costs of production will be recorded. The bio-engineering data will be used to assess RAS functioning and simple economic models will be created to evaluate the feasibility of commercial production of HSB in a RAS. The feasibility of disposal of HSB farm pond effluents via land application also will be evaluated by using water from eighteen research ponds stocked with HSB to irrigate 24 plots of land planted with various tree species. Pond water will be applied to the plots until standing water is observed and data on daily irrigation volumes and tree transpiration rates will be collected year round so that recommendations to industry on this type of effluent disposal system can be made. Additionally, the feasibility of determining the gender of Atlantic sturgeon via assay of sex steroid hormones in their blood, urine or mucus will be assessed to provide a means by which male fish can be identified and culled early in the caviar production cycle.