Blueberry Lake is in Ecological Lake Class 14, which consists of 92 lakes in northeast Minnesota that are very small and shallow, and have very soft (unmineralized) water.Blueberry Lake was slightly thermally stratified on 08/09/2005 with a surface temperature of 77 F and a bottom temperature of 72 F. Adequate oxygen for fish (more than 2 ppm) was present to within a foot of the bottom. Blueberry Lake has no inlets or outlet. Lake bottom substrates along the shoreline are mostly rubble, gravel, muck, boulder, and detritus. Aquatic plants grow to a depth of 7 ft and are sparse; the most common plant is bushy pondweed.Blueberry Lake is in Bear Head Lake State Park, and is accessible by a hiking trail. A State Park vehicle permit is required. Fish sampling in 2005 was done with two gillnets. Previously, a fisheries lake survey (1998) and a fish population assessment (2001) used three gillnets and two gillnets, respectively. Trapnets and shoreline seines were not used on Blueberry Lake due to the difficult portage access.Fish populations in 2005, as in previous investigations, consisted of high numbers of golden shiner and yellow perch. The catches of these species have declined over time, however.Golden shiner numbers in 2005 (7.0/gillnet) were lower than previous catches of 11.5/gillnet in 2001 and 25.7/gillnet in 1998. Golden shiner sizes in 2005 averaged 6.2", which was similar to their sizes in previous investigations on this lake. The largest golden shiner caught in 2005 was 6.7".Yellow perch numbers in 2005 (27.0/gillnet) were in the fourth quartile for this lake class, but were lower than previous catches of 30.5/gillnet in 2001 and 49.3/gillnet in 1998. Perch sizes in 2005 averaged 7.9", which was larger than the average size of 7.4" in 2001 and 7.0" in 1998. The largest perch caught in 2005 was 11.6". Perch scales were difficult to read, but it appeared that the growth of perch captured in 2005 was normal by area standards. After the initial investigation in 1998 revealed very high numbers of perch, attempts were made to establish a walleye population in Blueberry Lake that could prey on the perch. In 1999 33/lb walleye fingerlings were stocked at the rate of 0.74 lb/littoral acre (39 lbs), for a total of 1,287 fingerlings. Due to the difficult portage, the fingerlings were in poor condition when stocked. Walleye fry were stocked in 2002 and 2003 at the rate of 1,887/littoral acre (100,000 fry each stocking). No walleye were captured in 2001 or 2005, but the populations of golden shiner and yellow perch declined as though walleye had survived and were preying on these species. Many of the yellow perch captured in 2005 were infected with neascus (black spot), and some of the perch were infected with yellow grub. Both of these parasites are common and are native to the area. They cannot infect humans, are often removed by filleting fish, and are killed at temperatures used to cook fish.