A standard survey was conducted at Clear in 2016 to monitor the Lake's fish population. A total of seven different species were sampled in 2016, indicating low diversity. The lake was well mixed with good levels of oxygen at all depths, allowing fish to use the entire lake. The water clarity was poor (1.2' secchi disk reading) in 6/13/16, due to an intense algae bloom. Clear Lake had been overrun by Black Bullhead and Common Carp in the past, and was most recently reclaimed with rotenone in 2000. An aeration system was operated during the winter to reduce the likelihood and severity of winterkill at Clear Lake. Winter oxygen levels still dropped dangerously low some years (2010, 2011, and 2014), especially at the north end of the lake. A Brown County Park with a fishing pier was available to anglers.
Gill nets sampled low numbers (6) Walleye for a catch rate of 3.0/net, which was within the normal range for lakes similar to Clear. The 2011 catch rate was also low at 0.8/net. Historic catch rates (n=9), from 1984 to 2016 and under various stocking regimes, were highly variable ranging from 0.4 to 130.0/net with an average of 21.5. Gill net catch rates, following the latest reclamation (n=4) ranged from 0.8 to 7.5/net with an average of 3.3/net. Gill netted Walleye were 7.7 to 18.3 inches long with an average of 10.0. Trap nets sampled 1 Walleye that was 25.6 inches long. Fish were age-2 to age-7 with three year classes present. All of the gill netted fish corresponded with stocked year classes. This may indicate that natural reproduction was not significant at Clear Lake. Age-2 fish (2014 year class) made up the majority of the sample (83%) and that year class was actually moderate in size. Growth was slow. The latest fry stocking regime (252,000 every other year) was initiated in 2006. The stocking regime was modified in 2010 with hopes of producing a better Walleye fishery. The plan stated that if the fall electrofishing catch rate for young of the year Walleye fell below 50/hr., then 252 pounds of fingerlings would be stocked into Clear Lake. Fry and fingerlings were stocked in 2010, 2014, and 2016. Fingerlings were not stocked in 2012 due to poor condition and slow growth of the 2010 year class. The fingerling contingency was triggered 4 out of 4 times likely indicating that fry stocking was not working, possibly due to predation by the large population of Black Crappie. Walleye gill net catch rates (2011 and 2016), during the latest regime (2010), ranged from 0.8 to 3.0/net with an average of 1.9. A lack of forage, prior to 2016, could be what was limiting the Walleye fingerling stockings at Clear Lake.
Gill nets sampled moderate numbers (30) of Yellow Perch for a catch rate of 15.0/net, which was within the normal range for lakes similar to Clear and the highest ever measured at Clear Lake. Yellow Perch were stocked in 2009 to compete with Black Crappie and to provide an alternate forage base for Walleye. Historic catch rates (n=9) from 1984 to 2016 were mostly low, ranging from 0.0 to 15.0/net with an average of 2.0. Gill netted Yellow Perch were 5.6 to 6.7 inches long with an average of 6.0. Yellow Perch were all age-2, indicating inconsistent recruitment, but at least some natural reproduction was now occurring. Growth was fast.
Gill nets sampled moderate numbers (48) of Black Crappie for a catch rate of 24.0/net, which was above the normal range for lakes similar to Clear. The 2011 catch rate was extremely high (214.5/net). Historical catch rates (1984 to 2016) were highly variable ranging from 0.0 to 298.0 with an average of 96.2. Catch rates (n=4) since the reclamation (2004, 2006, 2011, and 2016) were mostly high, ranging from 24.0 to 298.0/net with an average of 206.6. In 2016, gill netted Black Crappie were 4.5 to 11.1 inches long with an average of 6.9. Trap nets sampled high (1,099) numbers of Black Crappie for a catch rate of 122.1/net which was above the normal range. The 2011 trap net catch rate was 76.6/net. Every trap net catch rate since the reclamation was above the normal range, indicating a large population. Historical catch rates from 1984 to 2016 (n=16) ranged from 0.0 to 148.8/net with an average of 60.7. Trap netted Black Crappie were 3.4 to 11.4 inches long with an average of 7.0. The overall size structure would be poor, but decent numbers of 10 inch fish were present. Black Crappie were estimated to be age-1 to age-11 with seven year classes present. At least two of the year classes (2013 and 2014) appeared to be quite strong, accounting for 40% and 55% of the catch, respectively. Growth was moderate.
Trap nets sampled low numbers (24) of Bluegill for a catch rate of 2.7/net, which was within the normal range for lakes similar to Clear, but was also the second lowest on record since the reclamation. The 2011 catch rate (55.0/net) was much higher. Catch rates from 1984 to 2016 (n=16) were highly variable ranging from 0.0 to 102.5/net with an average of 26.9. In 2016, trap netted Bluegill were 4.8 to 8.5 inches long with an average of 7.5. Approximately, 88% of the trap net catch was 7 inches or longer, indicating a quality size structure. In 2016, trap netted Bluegill were age-2 to age-7 years old with six year classes present. All year classes appeared to be weak. Growth was fast. Marginal submergent plant habitat is likely a limiting factor on Bluegill at Clear Lake. Low oxygen levels, in the northern part of the lake during severe winters, could also lead to mortality on Bluegill at Clear.
Spring night-time electrofishing, targeting Largemouth Bass, was not conducted in 2016, but trap nets sampled 2 fish. Trap netted fish were 9.1 and 17.7 inches long. Largemouth Bass were not aged. This species may also be susceptible to winterkill during harsh winters, despite aeration. A marginal aquatic plant community also limits this species.
Gill nets sampled high numbers (213) of Common Carp for a catch rate of 106.5/net, which was well above the normal range for lakes similar to Clear and was one of the highest catch rates ever recorded in the Hutchinson Fisheries Management Area. The 2011 catch rate was 2.8/net. Catch rates (n=9) from 1984 to 2016 were highly variable ranging from 0.0 to 106.5/net with an average of 13.8. Gill netted Common Carp 0.1 to 21.9 inches long with an average of 12.1. Trap nets sampled moderate numbers (32) of Common Carp for a catch rate of 3.6/net, which was within the normal range for this type of lake. Trap netted fish were similar in length to gill netted fish.
Gill nets sampled high numbers (283) Black Bullhead for a catch rate of 141.5/net, which was within the normal range for lakes similar to Clear. The 2011 catch rate was 54.5/net. The 2004 and 2006 catch rates were both 0.0/net. Gill netted Black Bullhead were 5.3 to 11.1 inches long with an average of 7.8. Approximately 96% of the gill net catch was under 10 inches in length, indicating a poor size structure. Trap nets sampled moderate numbers (291) of Black Bullhead for a catch rate of 32.3/net, which was within the normal range for this lake type. Historical catch rates from 1984 to 2016 were variable, ranging from 0.0 to 594.3/net with an average of 54.3. Trap netted Black Bullhead were 4.7 to 11.4 inches long with an average of 9.1. It took 11 years for Black Bullhead to show up in Clear Lake following the reclamation, and another 5 years to become overly abundant.