Microsatellite DNA Marker-assisted Selective Breeding of Striped Bass, Morone saxatilis

Abstract

Although the hybrid striped bass (HSB; female white bass, Morone chrysops x male striped bass, M. saxatilis) supports the fourth most valuable form of finfish aquaculture in the United States, neither parental species has been genetically improved. Expansion of the HSB industry is limited by culture inefficiencies associated with reliance on wild broodstock for annual fingerling production. Domestication and selective breeding are expected to increase production efficiency and to promote market expansion. Resource limitations currently prohibit the individual rearing of multiple larval families for striped bass performance testing, necessitating a breeding program that is based on communal rearing of progeny groups with molecular markers as genetic tags for offspring identification. This dissertation research addresses fundamental questions relevant to selective breeding of the male parent of the HSB, the striped bass, including:

(1) Evaluation of genetic variation within a captive striped bass broodstock population;

(2) Examination of the feasibility of communal rearing protocols based on microsatellite markers for progeny identification during performance evaluations of striped bass;

(3) Assessment of paternal variation in performance traits of striped bass at both research and commercial scale throughout the HSB production cycle.

Examination of three captive striped bass broodstock strains using three highly variable microsatellite markers revealed that the broodstock population contains moderately high genetic diversity, with an average allelic richness of 13.7 alleles per locus and an average observed heterozygosity of 0.84. Crosses among the three differentiated strains should provide a valuable starting point for establishing a highly variable base population for selective breeding.

Twenty-four experimental families were produced from captive, genotyped broodstock for communal evaluations of progeny survival and performance. Parentage was determined by microsatellite genotyping at six loci and more than 99% of progeny were attributable to a single sire-dam pair at each production phase and in all rearing environments. Application of large-scale communal rearing trials based on microsatellite markers for progeny identification should be a viable approach in a selective breeding program for striped bass.

There was limited evidence of family effects on early growth or survival to 35 days of age; however, significant paternal effects on growth performance, body shape, and carcass traits were detected at later culture stages and variation in antimicrobial peptide activity, a measure of innate disease resistance, differed by strain within the research ponds. In general, progeny of domesticated Santee:Chesapeake sires out-performed those of other strains both at research-scale and in the commercial tank. In research ponds, performance of fish as yearlings (Phase II) allowed prediction of performance at Phase III (18-20 months of age). Performance in research ponds also was predictive of Phase III performance in the commercial tank. Results from performance evaluations provide evidence of genetic variation in economically important traits which may be exploited for selective breeding of striped bass.

This research provides fundamental information needed to accelerate selective breeding and to increase production efficiency for the hybrid striped bass industry.