September 13, 2019
Researchers at South Dakota State University compared areas fished by bluegill anglers with habitats used by large bluegills in Enemy Swim Lake, South Dakota.* The extent anglers and bluegills overlap, along with angler catch success, affects harvest and can drive the effectiveness of regulations. The study also provides information on locations used by large bluegills across seasons.
Enemy Swim Lake is 2,150 acres with average and maximum depths of 16 feet and 28 feet, respectively.
Substrate is mostly silt, muck, and sand, with smaller areas of gravel, pebble, and cobble. Aquatic vegetation coverage peaks at 37 percent of the lake surface area in summer with less than 1 percent emergent vegetation.
Bluegills 8 inches and longer were tagged with radio transmitters and located several times per week over the course of a year, while over the same period anglers were interviewed and their locations recorded. Habitat also was inventoried throughout the lake and characterized at bluegill and angler locations.
During summer, bluegills and anglers used nearshore areas throughout the lake. In summer, depth and vegetation did not differ between anglers and bluegills, although bluegills used harder substrates than where anglers fished. In winter, bluegills and anglers were concentrated in shallow vegetated bays and nearshore areas. One particular large bay was extensively used by bluegills and anglers. In winter, bluegills occupied more heavily vegetated areas than anglers fished. Winter anglers fished deeper in areas with shorter and less dense vegetation than bluegills.
The researchers suggest that the use of heavily vegetated habitats in winter may create a refuge from angling, and anglers may have less of an effect on bluegill size structure during winter compared to summer when anglers and bluegills had more overlap.
*Weimer, E. J., M. L. Brown, and B. G. Blackwell. 2014. Quantifying differences in habitat between anglers and large bluegills. The Prairie Naturalist 46:4-10