Abstract
AbstractChannel catfish Ictalurus punctatus are commonly stocked into small impoundments and may become abundant in these waters. When channel catfish are abundant, they may compete with bluegills Lepomis macrochirus for macroinvertebrate prey, resulting in reduced growth and size structure of bluegills. I determined whether bluegill growth and size structure were related to the varying abundance of channel catfish by means of two experimental pond studies and small‐lake survey data. In the first pond experiment, 16 ponds were stocked with bluegills at 39.5 kg/ha and with channel catfish at a rate of 10, 30, 50, or 100 kg/ha (4 ponds/treatment). In the second pond experiment, 12 ponds were stocked with one of four bluegill–channel catfish biomass combinations (3 ponds/treatment): 15 and 70 kg/ha, 15 and 130 kg/ha, 70 and 70 kg/ha, or 70 and 130 kg/ha. Bluegill growth increments (both length and mass) did not decrease with increases in channel catfish biomass in either experiment, but both fish species exhibited density‐dependent growth. Macroinvertebrate biomass did not differ among treatments for either experiment. Bluegill proportional stock density, relative stock density for fish of 203 mm total length (TL) or more, relative weight, and mean TL at ages 3 and 4 for females and males did not differ among lakes stocked with 12, 37, or 74 channel catfish fingerlings·ha−1·year−1. However, channel catfish abundance varied greatly among lakes within a given stocking rate. When bluegill population characteristics were compared with channel catfish catch per unit effort (CPUE; fish/tandem hoop‐net series), there was a general pattern in which bluegill variables were highly variable at low to moderate channel catfish CPUE but consistently low at high channel catfish CPUE (>200 fish/tandem hoop‐net series). Thus, bluegill growth and size structure may only be reduced when channel catfish are highly abundant.
Published Version
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