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Home > Resources & Publications > Newsletters & Magazines > Fact Sheets > Bull Bream

Resources & Publications: Fact Sheets

by Jerald Horst

Bluegills, or as they are often called in Louisiana brim or perch, are a popular freshwater sportfish. In man-made bass/bluegill ponds, they are also the primary food source for bass. Most desirable for fishermen are the large colorful males, which can grow to more than 8 inches in length.

Unfortunately, some waterbodies, especially ponds and smaller lakes, can develop a dense population of “stunted” small fish. It is usually assumed that this occurs because there are too many bluegills present for the food supply. In response, fisheries biologists usually recommend fishing bluegills harder to “thin them out” and make room for larger fish. Sometimes this works, but often it doesn’t. Researchers in Illinois have recently done some work to figure out why these stunted populations develop and their research indicates that too much fishing pressure rather than too little may be the problem.

Large male bluegill are easiest to catch in the warm summer months when they are concentrated on their spawning beds. A bed may have up to 500 individual nests in a small concentrated area. Each nest is about the size of a large dinner plate or platter and is swept clear of silt and guarded by the male fish against other fish that will eat their eggs.

During the four month spawning season, males will be almost continuously on their nests for repeated spawnings. While on the nest, a male will eat very little and as a result grow very little. The best nest sites are those in the center of the bed, because egg-stealers enter a colony from the edges and usually don’t make it to the center.

Male bluegill compete intensely for these best sites and larger males usually win. In a population with a lot of large males, smaller males can’t compete and instead of becoming sexually mature, they delay maturation and grow for another year.

If, however, large numbers of big males are removed from the nests by fishing, these younger, smaller males stop growing and start spawning. This results is a stunted population, not because of slow growth, but because of early maturation.

Production of a healthy population of large male bluegills may be helped along by fishing heavily on smaller, younger bluegills, reducing the harvest of large male bluegills and keeping a strong bass population in the waterbody.

Download: bullbream.pdf (571KB)


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