THE FEASIBILITY OF STOCKING LARGEMOUTH BASS IN 0.04-ha MESOCOSMS USED FOR PESTICIDE RESEARCH

Abstract

Piscivorous fish can exert considerable influence on the structure and function of aquatic ecosystems. However, current U S . Environmental Protection Agency guidelines for aquatic mesocosm tests for pesticide registration assume that mesocosms with a volume of <1,000 m 3 are too small to support a piscivorous fish population. We tested this assumption between early April and mid-December by stocking ten 0.04-ha, 345-m3, earthen pond mesocosms with 30 adult bluegill and two of the 10 with 0, 10,20,40, or 80 fingerling largemouth bass. As the stocking rate of bass increased, the average size and condition factor of bass and the number of recovered juvenile bluegill decreased, whereas the average length and mass of juvenile bluegill increased. The total biomass of juvenile bluegill in each pond was not affected by bass stocking rate. Adult bluegill were not affected by bass stocking rate, except for a slight increase in total biomass in the 80-bass ponds. Bass stocking rate had marginal impacts on the crustacean zooplankton and no significant effect on emergent insects. The survival of reasonable numbers of juvenile bluegill over a wide range of bass densities indicates that 0.04-ha mesocosms can be feasibly stocked with piscivorous fish. The key is probably sufficient macrophyte abundance to provide cover for the juvenile bluegill.

Effects of Management Practices and Environmental Factors on Largemouth Bass Abundance in Illinois Inland Lakes

“…Management practices have also been shown to be ineffective ( [19] for fishing regulations; [20] [21] for fish stocking), possibly due to large variations in environmental factors.…”