Genetic Improvement of Aquaculture and Wildlife Management

Genetic data have the ability to transform traditional aquaculture and wildlife management practices making both more efficient and effective. Here, analyses of microsatellite markers were employed to answer three applied questions of vital importance to sustainable white sturgeon (Acipenser transmontanus ) caviar farming and the management of bighorn sheep (Ovis canadensis) in Arizona. In the first chapter, we examined whether the phenomenon of spontaneous autopolyploidy in cultured white sturgeon was maternal or paternal in origin. Flow cytometry identified spontaneous autopolyploids among multiple full-sibling families at two caviar farms. The sires and dams of each family and all progeny were genotyped at 12 microsatellite loci. The transfer of unique maternal alleles from broodstock to offspring was greater than that of unique paternal alleles in spontaneous autopolyploid white sturgeon suggesting that spontaneous autopolyploidy originates as a result of abnormalities in maternal meiosis. Knowledge of the source of spontaneous autopolyploidy will allow caviar farmers to make informed decisions regarding the management of fish with elevated genome size and whether to exclude these individuals from their cultured stock. In the second chapter, we investigated the association between highly variable roe yield and the proliferation of adipose tissue in the ovaries of culture white sturgeon. Caviar farmers frequently observe that sturgeon with lean ovaries tend to produce a greater yield of superior quality caviar compared to those with large amounts of ovarian adipose tissue. A feeding trial was performed to assess the impact of diet on ovarian adiposity and caviar yield in 7- and 8-year-old white sturgeon reared at two farms in California. On a subset of these same fish, the significance of the fixed effects of age at maturity, farm, diet, tank, and genotype on ovarian adiposity and caviar yield was tested and narrow-sense heritability was calculated. Sturgeon fed a low energy finishing diet had substantially less ovarian fat and a greater roe yield than those reared on a high energy finishing diet indicating that sturgeon farmers should first rear juvenile sturgeon on a high energy diet to obtain maximal body growth but then switch to a low energy finishing diet before harvest. Such a strategy would minimize the proliferation of ovarian adipose tissue and maximize caviar yield. Farm, diet, tank, and age all had large effects on ovarian adiposity and caviar yield in sub-sampled fish (P<0.05). Measures of ovarian fat and roe yield were moderately heritable (h2 ranged from 0.20 to 0.39). In the third chapter, we genotyped 40 microsatellite loci and sequenced 515-bp of the mitochondrial control region of Arizona desert bighorn sheep spread throughout 11 state game management units to assess population structure and genetic variation to inform management plans. Three distinct genetic clusters of bighorn sheep were detected in Arizona corresponding to three putative subspecies: two desert subspecies (O.c. nelsoni and O.c. mexicana) and one Rocky Mountain subspecies (O.c. canadensis ). Admixture between the two desert subspecies was evident in a single game management unit located in proximity to the Bill Williams River. There was little to no evidence of mixing between Arizona desert and Rocky Mountain bighorn sheep populations. Our study also revealed that bighorn sheep in northern Arizona appear to move among game management units more so than individuals in southern Arizona game management units. Furthermore, among samples tested, most bighorn sheep within game management units examined were not closely related. This work provides an important and robust foundation of genetic data and results for assisting decision-making in bighorn sheep management and for monitoring genetic diversity and population structure into the future.