Performance of Endangered Bonytails Fed Four Commercial Diets

Abstract

AbstractThe bonytail Gila elegans is a critically endangered cyprinid that is endemic to the southwestern United States, where it is cultured in ponds and water reuse systems as part of recovery efforts. Unlike in extensive outdoor pond culture, where natural food productivity plays a primary nutritional role, manufactured feed must provide complete nourishment for fish reared indoors in recirculating systems. The objective of this study was to determine the effects of diet on the growth and survival of juvenile bonytails fed four commercially available feeds over a 120‐d period. The four treatment diets were identified as a catfish diet, a trout diet, a high‐protein shrimp diet, and a low‐protein shrimp diet. Significant (P < 0.05) differences in growth among treatments were observed on sampling day 102. By day 120, the average weight of fish fed the high‐protein shrimp diet (36.3 g) was significantly higher than the weights of fish fed the catfish (26.6 g), trout (24.7 g), and low‐protein shrimp diets (24.2 g). The specific growth rates measured on days 102 and 120 were significantly greater for bonytails fed the high‐protein shrimp diet than for fish fed the other treatments. The feed conversion ratio of fish fed the high‐protein shrimp diet was significantly better than those of fish fed the trout and low‐protein shrimp diets, while the protein efficiency ratio and apparent net protein retention were generally higher in the high‐ and low‐protein shrimp diet treatment groups than in the other two treatment groups. Overall survival was high (93.5%) and did not differ significantly among treatment groups (P ≥ 0.05) through 120 d.