Lake sturgeon, currently designated as species of special concern or threatened in several Great Lakes Region states, have demonstrated successful growth and nutrient retention in previous studies involving young juvenile specimens (3-80 g body weight (BW)) fed formulated feed. This study aims to identify the optimal feeding rate for lake sturgeon and compare their performance with fish fed frozen bloodworms, a commonly used feed in lake sturgeon hatcheries for conservation purposes.
In this investigation, lake sturgeon with an average initial BW of 100.7±1.4 g (n=21) were fed a commercial feed (45% protein and 12% lipid) over a four-week period. Six feeding rates were tested: 0.25%, 0.5%, 1.0%, 1.5%, 2.0%, and 3.0% of BW per day. A reference group was fed frozen bloodworms at a rate of 1.20% dry weight of BW per day. The fish received three daily meals, with three tanks per treatment and 12 fish per tank. At the end of the feeding trial, the fish underwent an acute heat shock test, involving subjecting them to stress at 30°C for 20 hours. Results indicated that the optimal feeding rates for sturgeon fed the commercial feed were 2.8% and 1.87% of BW daily, based on specific growth rate and feed efficiency, respectively. Positive correlations were observed between feeding rates and condition factor, hepatosomatic index, and visceral fat. Increasing the feeding rate led to the accumulation of lipid and energy in the whole fish (P<0.05). Overall, growth performance and nutritional composition were comparable (P>0.05) between fish fed the commercial diet at 1.5% of BW per day and those fed frozen bloodworms. Serum glucose levels increased with higher feeding rates, displaying a positive response to heat shock stress in all treatment groups. Acute heat shock significantly increased the alpha-diversity of gut microbiomes and elevated serum cortisol levels in sturgeon, with bloodworm-fed fish exhibiting higher cortisol levels compared to fish fed the commercial feed at the 1.5% feeding rate. This suggests that fish fed bloodworms may be more vulnerable to stress. These findings imply that formulated feed can be a suitable alternative to bloodworms for raising lake sturgeon for stocking purposes.