Assessing Genetic Contributions to Performance of Communally Reared Families of Wild and Domesticated Reciprocal Hybrid Striped Bass.
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Date
2006-07-18
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Abstract
Expansion of the hybrid striped bass (HSB) aquaculture industry has been limited by high production costs dictating high prices. Much of the industry is dependant upon wild or captive broodstock. Selective breeding for an improved HSB may be one way to increase production efficiency driving down market prices and allowing industry expansion. Researchers at North Carolina State University have domesticated the HSB parental species over several generations (white bass, Morone chrysops and striped bass, M. saxatilis). This study compares performance (e.g., survival, growth) of HSB progeny from domesticated and wild broodstock that were communally reared in research and commercial ponds and provides an initial assessment of the degree to which important production traits have a genetic basis amenable to improvement.
HSB progeny were produced using commercial in vitro spawning techniques and a nested mating design with multiple white bass dams crossed with individual striped bass sires. At the time of spawning, cross combinations were recorded and blood (DNA) samples were collected from the broodstock. These samples were used to test the variability of 68 microsatellite DNA markers. The seven most variable markers were multiplexed and used for progeny identification (whole larvae and fin clips). Initial progeny samples were collected and genotyped at 2 days post hatch (dph) from aquaria of mixed parentage (N = 580) revealing a large variation in initial survival (0-68.9%). Larval samples (N = 438) were also collected and genotyped at 3-4 dph (Phase 0) after domesticated and wild progeny were mixed (volumetric ratio of 48:52). Fin clip samples were collected from progeny at the end of Phases I (≥ 35 dph; N = 761), II (~1 year of age; N = 909) and III (~1.5 years of age, market; N = 2789). Domesticated progeny experienced an increased rate of mortality within the first ~35 dph. This may have been a result of several beginning factors (e.g., variations in female broodstock fitness and initial stocking times) as significant variations were mainly evident between Phase 0 and Phase I-III progeny samples (pairwise comparisons of allelic frequency distributions P ≤ 0.00909, chi-square analyses P < 0.0001), whereas comparisons between later Phases (I-III) were less likely to differ significantly.
Large variations in family sizes prevented comparisons between progeny from all full sibling families (n = 33), but comparisons of progeny from paternal half sibling families (n = 5) was possible. Trends in ranked means of paternal half sibling progeny by length and weight indicated that progeny from domesticated crosses performed as well as or better than progeny from wild crosses. The progeny from domesticated crosses were a rounder shape by comparison of mean condition factors and landmark based geometric morphometric analysis (N = 1203 digital images in Phase III). The occurrence of external abnormalities differed between ponds as did the shape of HSB progeny (P = 0.0001) with a significant interaction effect for shape between ponds and paternal half sibling families (P = 0.0080) indicating large environmental effects. In Phase III progeny, females grew faster than males (P ≤ 0.0002) and also varied in shape (P < 0.0001), but an interaction between family and shape did not appear to exist. The full sibling families with the largest numbers of progeny were compared to determine differences in growth (length, weight) and shape. These comparisons indicated that an additive effect from both dams and sires exists in HSB progeny, however the study design did not allow for quantification of this effect. All of these results suggest that domesticated broodstock have maintained their value for commercial production of HSB and significant family variation is present that may be amenable to selective improvement.
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family-based performance variations, aquaculture, geometric morphometric analysis, hybrid striped bass
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Degree
PhD
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Zoology
