Comparison of Body Composition and Fatty Acid Profiles Between Wild and Cultured Rio Grande Silvery Minnow, Hybognathus Amarus

A major goal of conservation hatchery management is to create an environment as similar to the natural habitat as practicable.  One component of conservation management is to allow fish to forage on natural food organisms, rather than relying upon formulated diets. In this study, endangered Rio Grande silvery minnows (RGSM) were cultured in one of three regimes (indoor tanks with a hatchery diet, outdoor tanks with both natural food and diet supplementation and a refugium with only natural food).  After four months, total lipids along with fatty acid profiles were examined in each group and compared to wild fish.  Mean weight and percent body fat did not differ between wild fish and RGSM raised in the refugium (3.97-3.89 g; 7.8-8.3% respectively).  However, fish fed the hatchery diet with access (outdoor tanks) or without access to natural food sources (indoor tanks) had much higher percent fat (10.6 ± 0.1 and 15.5 ± 0.5, respectively).  In this respect, refugium fish appear more similar to wild fish than RGSM fed in either the two hatchery regimes.  Comparison of fatty acid profiles among groups showed marked differences in FA content between wild fish, refugium fish and those fed the hatchery diet.