Population social structure and gizzard shad density influence the size-specific growth of bluegill

Many bluegill (Lepomis macrochirus) populations are stunted and consist mainly of smaller individuals. There has been much recent interest in determining factors that influence the growth of bluegill so that management remedies can be designed to alleviate stunting. Bluegill population size structure is unlikely controlled by any one factor. Instead, multiple variables likely interact to regulate adult size. We used Akaike's information criterion to determine how various environmental variables influence the size-specific growth of bluegill at 50, 100, and 150 mm total length (TL) in 16 lakes. Eight models related to prey availability, lake productivity, lake habitat, predation pressure, intraspecific competition, angling pressure, gizzard shad (Dorosoma cepedianum) density, and population social structure were constructed. Population social structure had the greatest effect on the size-specific growth rates of fish at 50 mm TL. At this size we found a significant negative relationship between size-specific growth rates and the mean age of maturation of males in the population. Size-specific growth rates at 100 and 150 mm TL were negatively related to gizzard shad density. These results suggest that management actions that help to increase the numbers of large males and reduce gizzard shad density would help alleviate stunting in bluegill populations.