Influence of Lineage, Broodstock Conditioning, and Hormone Injection on Gila Trout Reproductive Success and Egg Fatty Acid Composition

Abstract

AbstractSuccessful reproduction of captive‐reared fishes depends on hatchery practices and proper broodstock nutrition. Nutrient requirements and environmental conditions stimulating reproductive development are unknown for many threatened and endangered species and may differ between lineages within species. Accordingly, prior to spawning, Main Diamond Gila Trout Oncorhynchus gilae broodstock were exposed to different thermal cycles and hormonal injection to improve reproductive success. Additionally, egg fatty acid composition and hatching success of Main and South Diamond Gila Trout were evaluated to determine the extent of phenotypic differences between lineages. Thermal conditioning of broodstock accompanied with injections of exogenous luteinizing hormone releasing hormone analog (LHRHa) prior to spawning improved progeny survival over historic hatchery means as well as means for broodstock reared in raceways at constant temperatures without LHRHa. Egg n‐6 fatty acid content appears to be associated with this improvement. Eggs from Main and South Diamond broodstock fed the same feeds had similar hatch rates but could be differentiated on the basis of fatty acid profile. Future trials should further evaluate the influence of dietary fatty acids on egg deposition and hatch rate, while acknowledging that changes in reproductive performance may differ across lineages. Broodstocks should continue to be conditioned with thermal cycling and use of LHRHa to induce ovulation, as these techniques resulted in significantly better hatch rates in the current study than use of only photoperiod manipulation to stimulate reproductive development.