Growth and Appetite of Juvenile Lake sturgeon Acipenser fulvescens

–Growth rates of juvenile lake sturgeon (initial weight 8 to 9 g, temperature 17.5° C), fed twice a day on brown worms for 56 days increased from -1.5% BW/d (% body wet weight/day) at zero ration to 2.6% BW/d at a ration of 13.2% BW/d. Maintenance ration was 1.6% BW/d. Fish fed larger rations had higher energy densities and lower water content. Appetite (average volitional daily food consumption) was compared for lake sturgeon initially weighing 6.3 g fed once and twice a day. Appetite was 12.8±1.6% BW/d (n=36) for fish fed twice daily compared to 7.4±0.8% BW/d (n=36) of fish fed once a day. Growth rates and food consumption in single feedings per day averaged 1.8±0.2% BW/d and 9.4±2.2% BW/d respectively, and were independent of weight for lake sturgeon weighing from 10 to 1322 g. These growth patterns are similar to other fish species. The most prominent feature of lake sturgeon growth was variation in daily food consumption, by as much as 15-fold for fish fed twice a day. Daily food consumption was correlated with previous consumption history, but mechanisms causing the effect could not be determined. The ability to gorge may be important for a species feeding on patchy prey. Management of lake sturgeon would be facilitated by selecting larger fish for stocking. The lake sturgeon Acipenser fulvescens is a unique freshwater fish because of its longevity, slow growth, late maturity, large adult size, and relative rareness (Probst and Cooper 1954). This combination also makes the lake sturgeon extremely sensitive to exploitation, resulting in the historical decline of the lake sturgeon fishery (Houston 1987; Fortin et al. 1993). Only in recent years has management of lake sturgeon stocks, primarily by stocking and closure of fishing, begun to rebuild populations severely reduced by past human activities (Brousseau 1987; Fortin et al. 1993). As lake sturgeon populations rebuild, it is important to evaluate the carrying capacity and population size supportable by available habitat. Such information cannot be obtained from a census of existing populations because these are depressed. An alternative for evaluating carrying capacity is to compare food resources and their use by lake sturgeon populations using information on growth and production energetics. This may be especially important for