Rearing Density Impacts Juvenile Bluegill Lepomis macrochirus Growth in a Recirculating Aquaculture System
The effects of rearing density on large juvenile bluegill Lepomis macrochirus growth in recirculating aquaculture systems are relatively unknown. This 63-day study evaluated three initial densities: low (6 kg/m3), intermediate (12 kg/m3), and high (18 kg/m3). Final densities were low (8.1 kg/m3), intermediate (16.6 kg/m3), and high (20.9 kg/m3). At the end of the study, fish reared in the low-density tanks had a mean (SD) weight of 95.99 (7.49) g, which was significantly heavier than the 75.70 (4.28) g mean weight of fish in the high-density tanks. At 86.23 (7.63) g, the weight of individual fish in the intermediate-density treatment was not significantly different from either the low or high-density treatments. Specific growth rate was also significantly greater in the low-density treatment than in the high-density treatment. Individual fish total lengths were not significantly different among densities, with mean (SD) values of 155 (4) mm, 152 (4) mm, and 148 (2) mm for the low, intermediate, and high-density treatments, respectively. Similar to fish weight, condition factor was significantly greater in the low-density treatment than in the high-density treatment, while condition factor in the intermediate-density treatment did not differ significantly from the other treatments. Tank gain, percent gain, and feed conversion ratio did not differ significantly among treatments. These results indicate that of the three bluegill rearing densities evaluated in this study, the intermediate initial density of 12 kg/m3 appeared to produce the best balance of individual fish growth and total biomass production.