Growth, Food Consumption and Energy Status of Age-0 Pallid Sturgeon (Scaphirhynchus albus) Fed Commercial or Invertebrate Diet

Stocking of hatchery raised pallid sturgeon (Scaphirhynchus albus) is an important part of the pallid sturgeon recovery program.  Little is known about sturgeon dietary needs and hatchery raised pallid sturgeon are currently fed commercial diets that are formulated for salmonids.  It is unknown whether these commercial diets are well suited for pallid sturgeon.  Our objectives were to compare growth, consumption, energy density, routine metabolic rates, and liver condition of pallid sturgeon fed formulated and natural diets.  Twenty four pallid sturgeon were fed a daily pre-weighed ration of either commercial pellets (Silver Cup, 1 mm), or frozen chironomid larvae for 6 weeks.  Adjusted routine metabolic rates (g O₂/d)/wt^0.85, growth (g), adjusted daily caloric intake (Cal/day)/wt^(0.674), energy density (cal/g wet weight) and a hepatosomatic index were compared between diets using a 2-sample t-test. Pallid sturgeon fed chironomid larvae exhibited faster growth, higher metabolic rates, higher energy density and lower hepatosomatic index.  Natural feeds were superior to formulated diets in all comparisons.  Juvenile pallid sturgeon primarily consume aquatic insects, and therefore are physiologically adapted to efficiently process chironomids, rather than formulated feeds.  Use of a natural diet prior to stocking may maximize growth and post-stocking survival for hatchery reared pallid sturgeon.