STRIPED BASS STRAIN EFFECTS ON AQUACULTURE PERFORMANCE TRAITS, STRESS RESPONSIVENESS AND HYBRID OFFSPRING GROWTH

Striped bass (Morone saxatilis) and their hybrids have been well studied and are widely cultured as a food and gamefish. Recent increases in striped bass aquaculture have generated interest in domestication programs where growth performance and stress tolerance are among the traits of interest. Unique geographic stocks, or strains have previously been identified and these populations will presumably exhibit distinct culture traits across different environments. Before application of genetic principles, domestication programs should begin by evaluating available strains for superior performance in the environments intended to be utilized during culture. In this effort, a series of experiments were conducted to better understand growth and stress in Morone culture with applications for genetic improvement. First, 7 strains of striped bass spanning the native range of the species and one domesticated strain were compared for growth at different salinities (0, 5, 30 ppt) until two years of age (~ 2.6 kg). Significant differences were found among and within strains for growth rate, feed conversion ratio and body shape but salinity had no effect on growth. Second, to observe paternal strain effects on hybrid growth, striped bass males representing four wild strains from the previous trials and the domestic strain were conditioned until maturity and manually spawned with white bass. Resulting hybrid offspring were grown communally in three size grade treatments (large, small, ungraded) and two culture environments (indoor recirculating tanks, outdoor tanks) until attaining market size (~ 680 g). Genotyping after final measurements permitted parental assignment of hybrids to sires. Differences in final weight and body shape were found among hybrids with highly similar performance trends to the previously conducted pure striped bass trials, suggesting a paternal strain effect. In addition to growth comparisons, two studies were conducted to compare stress responsiveness of striped bass during exposure to common aquaculture conditions. The first experiment investigated techniques to mitigate stress during transportation and demonstrated synergistic effects of anesthetic drugs that improve fish welfare during handling. In the final study, a suite of physiological parameters were measured in 4 strains of striped bass after 14 weeks exposure to a repeated, acute net chase stressor, and compared to an unstressed control group. The study demonstrated reduced performance of most strains and differences were detected among some measured responses. No single strain (wild or domesticated) demonstrated maintenance of growth or immunocompetence, but correlations among stress biomarkers were identified and variations within strains described for potential future research. This work contributes to a growing body of literature on striped bass aquaculture that could be applied in the design of region-specific broodstock programs, general culture practices and stress physiology studies