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Predators are often categorized as either cruise or ambush feeding strategists. We present evidence that white crappie (Pomoxis annularis) are neither. Instead, the crappie swim intermittently and search only when stationary. If the crappie searched while swimming, one would expect the run speeds to be slower than the pursuit speeds, but no difference was found between these two measurements. Assuming that prey are located while swimming, a foreshortening of runs prior to pursuit would also be expected, but again, none was detectable. The duration of the search pause appears to be related to the detectability of the prey. Crappie also search during the pause immediately following the attack and ingestion of a prey item. The observation that the probabilities of detecting and pursuing a prey following a run or an attack do not differ significantly supports this conclusion. Also, the duration of the pause following a run or attack does not differ significantly over a wide range of temperatures. If these views are correct, white crappie could not forage optimally by either deleting located prey items from the diet or minimizing handling time. What they appear to be doing is creatively managing their search time.

A mesocosm study of pesticide effects was conducted between November 1987 and November 1988 using 0 04‐ha earthen ponds The bottoms of the ponds were covered with sediments from an old farm pond, filled with aged reservoir water, and stocked with fifty 11‐ to 17‐cm blue‐gill sunfish Importing mature communities rapidly produced taxonomically rich ecosystems Coefficients of variance among ponds for taxonomic richness and population densities were modest (typically 10–30%) and usually inversely related to abundance Unchecked bluegill reproduction resulted in expected effects on lower trophic levels Crustacean zooplankton were nearly eliminated, which led to poor growth of the juvenile bluegill Phytoplankton densities appeared to increase as grazing pressure from zooplankton was reduced Insect emergence was not obviously impacted by fish predation Potential indirect effects on fish, such as growth impairment caused by pesticide induced reduction of food supply, could be obscured if zooplankton were nearly eliminated by over‐predation This suggests a need to control bluegill reproduction to achieve a more balanced ecosystem

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.