GROWTH, SURVIVAL, AND FATTY ACID COMPOSITION OF COPPERNOSE BLUEGILL (Lepomis macrochirus subspecies) OFFERED DIFFERENT WINTER FEEDING REGIMES

Winter fish losses are routinely reported by Arkansas sportfish producers in the spring. Juvenile Centrarchid species (< 7.6 cm) are quite susceptible to harsh winter conditions. While some of these winter fish losses can be attributed to predation by fish eating birds and water quality factors, water temperature is also an important contributing factor. Winter feeding strategies vary widely among sportfish farms in Arkansas. While some farmers feed routinely on a weekly basis as weather permits over the winter months, others feed much less frequently. In order to investigate the effect of different feeding regimes on winter fish losses, indoor and outdoor trials with coppernose bluegill (Lepomis macrochirus subspecies) were conducted during the winter of 2015. The first experiment was conducted in the laboratory in a temperature controlled recirculating tank system (600 L) equipped with nine tanks. Fish were initially stocked at ambient temperature and the temperature was reduced to 8°C over the course of seven days to mimic winter conditions. Fifteen coppernose bluegill (2.57 ± 0.10 g) were stocked into each tank. When the target temperature (8°C) was reached, three dietary feeding regimes utilizing a commercial 35% protein feed were implemented (3 replicates per treatment) that included feeding 1% body weight twice per week (2x/wk), once per week (1x/wk), or once per month (1x/mo) throughout the trial. After 13 weeks of culture, there were no significant differences (P>0.05) in final weight, survival, or condition factor of fish from the indoor trial. Substantial weight loss occurred across all three treatments, ranging from -14.64% to -18.87%. The outdoor feeding trial was conducted at the University of Arkansas at Pine Bluff Aquaculture Research Station with coppernose bluegill using static tanks (400 L). Unlike the indoor trial, fish were subjected to fluctuating, ambient winter temperatures in 16 static tanks, equipped with aeration supplied from a regenerative blower. The tanks were filled with pond water and stocked with 25 coppernose bluegill (2.59 ± 0.19 g) per tank. Fish were assigned one of four feeding regimes at 1% body weight that included feeding 2x/wk, 1x/wk, 1x/mo, or twice per month (2x/mo). Temperatures in the outdoor trial ranged from 0.10 - 16.3ºC.  Following 13-weeks of feeding, there were no significant differences (P>0.05) in final weight, weight gain, or condition factor. However, fish fed either 2x/wk or 1x/wk had significantly higher survival (P<0.05) than fish fed 2x/mo or 1x/mo. Weight gain ranged from -4.71 (2x/wk) to -10.74% (1x/mo). Results indicate that regardless of feeding regime, weight loss in coppernose bluegill occurred at low temperature after 13-weeks of culture. Whole body fatty acid profiles are currently being analyzed for treatment effects; however, results to date from the outdoor trial suggest that feeding 1x/wk or 2x/wk may be a beneficial strategy for commercial sportfish producers to increase survival and reduce weight loss of coppernose bluegill during the winter months.