The Pacific lamprey Entosphenus tridentatus is an ancestral species of critical importance to the ecosystem and indigenous cultures in the Pacific Northwest. Conservation aquaculture has been proposed as a potential technique to restore Pacific lamprey populations. Intensive culture methods and diets for this species have not been developed. A sixteen week feeding trial tested the effects of seven diet treatments on the survival, growth, fatty acid profile and whole body lipid content of Pacific lamprey ammocoetes. Dietary treatments were: active dry yeast, yeast plus fish oil emulsion, micro‐algae, micro‐algae plus fish oil emulsion, yeast with micro‐algae, yeast with micro‐algae plus fish oil emulsion and yeast with larval fish diet. Each diet was offered to five replicate tanks stocked with 20 ammocoetes that were 51 days post hatch. Survival during the trial was not affected by diet. The greatest length and weight increases were in fish fed diets containing yeast. Growth decreased as the amount of algae in the diet was increased. Lipid retention was significantly higher in fish fed yeast with larval fish diet relative to the other treatments. Feed conversion ratio was lowest in fish fed diets containing yeast. Whole body fatty acid profiles tended to reflect the fatty acid profile of the diet. Percentages of 20:5n‐3 and 22:6n‐3 were significantly higher in fish fed diets containing fish oil emulsion. Overall, yeast with larval fish diet provided the best growth performance in larval Pacific lamprey.

Soluble canola protein concentrate (SCPC) is rich in glutamic acid and may act as a feed attractant to improve feed acceptance and production performance of fish fed plant‐based diets. In the first experiment, attractant properties of SCPC were evaluated by comparing production performance of sunshine bass, Morone chrysops × Morone saxatilis, fed reduced fish meal (FM) diets supplemented with 1% SCPC or a betaine‐based feed attractant. In the second experiment, production performance of fish was compared after feeding reduced FM diets with or without SCPC. Following the first experiment, production performance was similar among fish fed attractants, but at 0% FM weight gain and survival were significantly lower compared to the 30% FM control treatment regardless of attractant inclusion. According to broken‐line analysis of data from the second experiment, the critical breakpoints in dietary FM inclusion rates needed to achieve maximal weight gain were similar regardless of SCPC. However, weight gain observed among fish fed SCPC was significantly greater than fish not fed SCPC. Including FM in plant‐based sunshine bass diets at rates >10–13% dry matter did not improve weight gain, and weight gain is optimized when a feed attractant/palatant such as SCPC is included in these plant‐based diets.

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Successful 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.