Distribution, abundance, and mortality of small littoral-zone fishes in Sparkling Lake, Wisconsin
During 1982 and 1983, seining, fyke netting, and SCUBA observation were used to determine the depth distribution, abundance, and mortality of small littoral-zone fishes (bluntnose minnows, shiners [primarily mimic shiners], yellow perch, logperch, johnny darters, Iowa darters, and mottled sculpins) in Sparkling Lake, a small moderately-productive lake in northern Wisconsin. During the summer cyprinids, darters, and mottled sculpins were most abundant in areas shallower than 1 m, while yellow perch were most abundant at depths of 2 to 4 m. Between August and October cyprinids and yellow perch moved to water 1 to 2 m deeper, while the depth distributions of darters and mottled sculpins generally remained unchanged. Large within- and between-year variations in abundances and mortality rates were evident for all species. In 1982, most of the mortality of cyprinids and darters occurred during a short period in late spring and early summer, with relatively little afterwards. In 1983, this pattern was reversed for cyprinids and Iowa darters, but not logperch and johnny darters. Between-year differences in abundance were greatest for young-of-the-year yellow perch; they were 400 times more numerous in 1983 than in 1982. Darters had their lowest mortality rates and highest reproductive success in 1983, while the opposite was true for cyprinids. This lack of synchrony between darters and cyprinids suggests that these two taxa responded differently to changes in environmental conditions in Sparkling Lake. Predation may have accounted for much of the variability in darter population parameters, but appeared to be a less important source of variation for cyprinid population parameters.