Bluegills: Biology and Behavior

8: Management


Managing a body of water scientifically and preferentially for bluegills requires knowledge of the habitat’s accessible components and control over its most ferocious size-selective predator, the angler. Management strategies traditionally focus on five variables: (1) water quality, (2) lower elements of the food chain, (3) the fishes, (4) the aquatic vegetation, and (5) the angler. What we know is never certain because each lake is dynamic and possessed of unique vulnerabilities. I shall focus on some of what we think we know and how, in sweeping terms, it might be useful.

The quality of bluegills inhabiting a lake or pond is an assessment based on their relative abundance, population size structure, condition, and growth. These defining elements are linked intimately with parallel attributes of their predators, mainly largemouth bass. Bluegills less than 150 mm TL are typical of small Midwestern ponds containing largemouth bass longer than 300 mm TL, but the trend is reversed when the bass are at high concentrations and smaller (200–290 mm TL).1077 For example, in 1965 at Deer Ridge Lake, Missouri, only 10% of the bluegills exceeded 150 mm TL, but more than 60% of the bass were 200–225 mm TL.1078 A minimum length limit of 300 mm TL was imposed for largemouth bass in 1969, and from 1971 to 1973 bluegills larger than 150 mm increased to 54–69% of the population.1079

These findings have been affirmed in a more recent investigation of 13 South Dakota ponds where bluegill quality improved with increasing numbers of smaller bass.1080 High bluegill quality in Nebraska’s Sandhill lakes was associated strongly with high relative abundance of largemouth bass of less than 300 mm TL.1081 Bass populations of extended size structure and low relative abundance were associated with bluegills of lower quality. Largemouths exerted greater influence on bluegill quality than in Minnesota lakes, but the Nebraska lakes also held fewer species of piscine predators.