Johnson Lake has been part of a fisheries research project (Study #635) that is evaluating stocking regimes for walleye in four lake classes. The evaluation included fry, small fingerlings, and three densities of larger fingerlings. As part of the evaluation, special assessments (gill net only) were conducted in 2002, 2004, and 2006, and the 2008 population assessment was also included. Johnson Lake received OTC marked walleye fingerlings in 2001, 2003, and 2005. In 2001, walleye fingerlings rated at 13/pound were stocked at a density of 1 lbs. per littoral acre (LA), in 2003 fingerlings 3.3/pound were stocked at 2lbs./LA, and in 2005 fingerlings 35/pound were stocked at 0.5lbs./LA. The greatest numbers of walleye fingerlings were stocked in 2005, even though the stocking rate was the lowest.
The walleye catch rate in 2008 was 1.7/gill net, which was at the lower end of the expected range. This is a modest increase from the 2006 assessment (1.3/net). Lengths ranged from 11-22 inches with a mean of 15 inches. Of the 10 fish sampled in gill nets, nine were aged. Six of these fish were age 3 and had an OTC mark indicating they were stocked. The remaining three were age 8 from the 2000 year class, which was a fry stocked year. The fry in 2000 were not treated with OTC and the contribution from that stocking cannot be determined. Growth was similar to the statewide average.
It appears that the small fingerling stocking, even at a low density, was better at establishing a year class in Johnson Lake. Similar to the previous assessment, no fish were sampled from the large fingerling/high density stocking that occurred in 2003. While no fish were sampled from the moderate fingerling density in 2008, one was sampled in 2006, and two were sampled in 2004. Fisheries research staff will analyze the data for all the lakes involved to determine the most effective stocking regime.
Northern pike were sampled at the upper end of the expected range. Catch rates from previous assessments tended to be variable with rates at either the high end or low end of the expected range. Lengths ranged from 15-29 inches with a mean of 20 inches. Size structure was poor with only four fish exceeding 24 inches in the sample. Scale and bone analysis indicated six year classes with fish age 2 through 7 present. Growth was similar to the statewide average.
Bluegill were sampled at a rate near the middle of the expected range. Previous rates have never been observed within the expected range. Lengths ranged from 3.5-8.7 inches with a mean of 6.1 inches. Black crappie were sampled above the expected range, however most lengths were typically small, eight inches or less.
Important prey species like yellow perch and white sucker were sampled within the expected range. Yellow perch were typically small and would not interest most anglers. Tullibee catch rates were lower than expected, yet similar to previous assessments.
Other species sampled include black bullhead, bowfin, brown bullhead, one largemouth bass, pumpkinseed sunfish, rock bass, and yellow bullhead.