Growth, food consumption, and energy status of juvenile pallid sturgeon fed natural or artificial diets
Stocking of hatchery-raised fish is an important part of the pallid sturgeon Scaphirhynchus albus recovery program. In the wild, juvenile pallid sturgeon consume primarily aquatic insects, although little is known about specific dietary needs. In hatchery settings, pallid sturgeon are fed commercial diets that are formulated for salmonids. To compare food consumption, growth, and energy status of pallid sturgeon fed artificial or natural diets, we conducted a laboratory study using 24 juvenile pallid sturgeon (initial fork length 153–236 mm). Pallid sturgeon were fed a daily ration of either commercial pellets (1 mm, slow sinking; 45% protein, 19% fat) or chironomid larvae for 5 wk. Natural-fed pallid sturgeon exhibited a greater specific growth rate (2.12% d −1 ) than pellet-fed fish (0.06% d −1 ). Similarly, relative condition was greater for natural-fed sturgeon ( K n = 1.11) than that observed for pellet-fed fish ( K n = 0.87). In contrast, the hepatosomatic index was significantly higher in pellet-fed fish (2.5%), indicating a high lipid diet compared with natural-fed sturgeon (1.4%). Given the importance of natural diets to fish digestion and growth, it is suggested that a more holistic approach be applied in the development of a practical diet for pallid sturgeon that incorporates attributes of natural prey.