Lepomis macrochirus Rafinesque, 1819: bluegill

Biological Description

Body compressed, very short and deep, the greatest depth at the third dorsal spine. Head deep, narrow; angle of dorsal surface moderately steep; opercular flap rather long, broad, and bluntly rounded with a black fexible tip; mouth terminal, slightly oblique, lower jaw slightly longer than upper jaw; brushlike teeth on jaws and vomer. Pectoral fins long and pointed; dorsal fin spines 10; a dark botch near middle of posterior rays; anal fin spines 3; scales ctenoid, 38-44 in lateral line. Adults yellowish-olive to dark olive-green above with bluish luster; sides bluish; breast and belly yellowish, shading to light orange in breeding males.Side with 5-10 vertical bars, usually more prominent below the lateral line.

 Life History

Generally, bluegill mature when 2 or 3 years old. However, maturity appears to be related to growth and the fastest growing fish mature sooner than fish that grow slowly. Bluegill spawn in the spring when water temperature is approximately 67° F. Spawning begins in April in Alabama waters, early May in Ohio, late May in Illinois and Wisconsin, and early June in Michigan. In Idaho spawning may extend from late May through August. Wisconsin spawning continues from late May to early August and peaks in June. Males generally form hollows for nests in a sandy bottom in shallow water. Females are only permitted access to the nests when ready to lay eggs. The eggs and milt are extruded at the same time, and since they are adhesive, stick to the substrate until hatching in about 5 days. The number of eggs produced by a female varies from 2,360 to 49,400 and depends on her size. As many as 68,815 fry have been collected from a single nest. This number indicates that several females may spawn with one male. After spawning, the male vigorously protects the nest and keeps the eggs clean and aerated by fanning them with his fins. After hatching, the fry are protected for several days by the male. Newly hatched bluegill are about 0.1 inch long.

Geographic Distribution

The native range of the bluegill extends from northern Minnesota and southern Ontario, eastward to Quebec, then south along the Atlantic seaboard to Georgia, then west to Texas and northeastern New Mexico and north to Minnesota. It has been widely introduced.

Habits and Habitats

Bluegill usually inhabit warm, shallow lakes with rooted vegetation. They have adapted well to some California reservoirs in which the water fluctuates and rooted vegetation is absent. They travel in small, loose schools while feeding, particularly in early morning or in the evening. Because they feed by sight, they feed primarily during daylight. Bluegill grow fastest in water temperatures between 60° and 80° F.and can survice temperatures up to 85° F. During mid-day bluegill go to deeper wates of shallow lakes or beneath the shade of trees or brush. The young remain in shallow water during the summer High turbidity is probably detrimental to successful reproduction and good growth.

Bluegill easily become stunted in some lakes, particularly in waters that are infertile or have dense vegetation The largest bluegill on record is a 15-inch specimen that weighed 4 pounds 12 ounces, taken from Ketona Lake, Alabama. The largest bluegill taken in Idaho was 3.5 pounds and was taken from CJ Strike Reservoir in 1966. The average size, however, is 8 inches and 0.5 pounds or less.

Diet

Bluegill fry eat zooplankton—principally crustaceans such as copepods and cladocerans. As they increase in size, they eat increasing proportions of various aquatic insects. Other foods include molluscs, small crayfish, amphipods, and fish eggs. Terrestrial insects such as grasshoppers are sometimes important in the diet. During summer, bluegill may eat plants such as algae and higher rooted plants. They continue to feed in winter (sometimes can easily be taken by angling through the ice), but the consumption of food decreases drastically when water temperatures drop below 55° F.

Idaho Conservation Status

Idaho Native or Import

Introduced. Most of the lake and pond waters of Idaho are too cold to support good growth. In Idaho its distribution has been limited to a few farm ponds in the Moscow area and a limited number of ponds and lakes of the southwestern and southeastern parts of the state.

Comments

Bluegills have an excellent reputation as a sport fish, particularly when taken with a fly on a fly rod or light spinning rod. They may be taken on a variety ofbaits, lures, and artificial flies. The flesh is excellent in quality. Most fishermen prefer to fillet larger fish.

Credits

Simpson and Wallace 1982.Wydoski and Whitney 1979. Image Copyright Joseph Tomelleri. Used by permission

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