This assessment was done in cooperation with Cook County water planning staff, as part of a water quality study on Mink, Kimball, and Boys Lakes. It was also done to monitor performance of stocked trout, and to determine the effects of yellow perch and rock bass on that performance.
Yellow perch and rock bass remained abundant in Kimball lake in 2013. Although yellow perch did provide some angling opportunity (a third of the fish taken in gill nets were over eight inches in length), they would also have been competing with rainbow and brown trout for available forage. The rock bass gill net catch far exceeded the normal range for a lake of this type, but rock bass collected in 2013 were small, and would have provided very little angling opportunity. No new undesirable fish species were collected in 2013. The source of the rock bass found in this lake is unknown, but they were likely put into the lake illegally. No rock bass had ever been found in Kimball Lake, or in any lake or stream in the Kimball Creek watershed, prior to their first appearance in Kimball Lake in 2009. The species is not common in Cook County.
The 2013 rainbow trout gill net catch was was about average compared to catches typically seen in the fall in stream trout lakes in this area. Although rainbow trout yearlings had been stocked annually in the years prior to this assessment, most of the fish taken in 2013 were one-year-old fish from the 2013 yearling stocking. Growth of those fish between the time they were stocked and the time they were collected in this assessment seemed to have been poor. Rainbow trout yearlings (one-year-old fish) stocked in the spring of 2013 weighed an average of 0.37 pounds per fish, while one-year-old fish taken in quarter-inch trap nets and gill nets in September 2013 weighed an average of 0.33 pounds per fish. In many stream trout lakes in this area, stocked yearlings can double their weight over the summer. Competition from yellow perch and rock bass probably resulted in poor growth in Kimball Lake.
The only brown trout collected in 2013 was a survivor from the 2009 fingerling stocking. Growth of that fish had been slow by area standards; it reached a length of 13.9 inches at the end of its fourth year, compared to an area average of 16.1 inches. Few Cook County lakes have been managed for brown trout, and gill net catches in those lakes have typically been lower than catches observed for other stream trout species.
Several splake were collected in Kimball Lake in 2013. All would have been migrants from Mink Lake, where splake fingerlings were stocked annually through 2012. Although splake are usually present in Kimball Lake, their numbers tend to be low compared to lakes (like Mink) that are directly managed for splake.
Kimball Lake is scheduled to be rehabilitated for stream trout management in the fall of 2014, with the goal of eliminating yellow perch and rock bass. All fish present at that time would be killed, and the lake would be restocked beginning in the spring of 2015.