The Bluegill is a deep, slab-sided sunfish with a rather small mouth. The upper jaw does not reach the front of the eye when the mouth is closed. The spiny dorsal fin has 10 spines and is joined broadly to the soft dorsal fin, but there is no notch. The pectoral fins are long and pointed and extend past the eye when they are bent in a forward position. There is usually a black spot or blotch near the base of the soft dorsal fin and a black, flexible tip on the gill cover. The back and sides are colored dark olive green with emerald and brownish reflections. The breast and belly are yellow or reddish-orange. Males in breeding colors often have a deep red, almost dark brown breast. The sides usually display vertical bars, but these are more prominent in smaller fish. The chin and gill covers are bright blue, giving the bluegill its name.
Bluegill is the most abundant and widespread member of the sunfish family in Iowa. It is found in nearly all waters of the state but is far more abundant in lakes and ponds than is streams and rivers. This fish is not commonly found in the western Iowa streams but in occasionally found in most eastern Iowa interior rivers. It is very abundant in the backwaters and sloughs of the Mississippi River.
Aquatic insects, small fish and crayfish.
3 lbs 2 oz; 12.88 in. - Farm Pond, Madison County, July 1986 - Phil Algreen, Earlham, Iowa
Use small hooks (#8) with a long shank when fishing with live bait for Bluegill.
The Bluegill is Iowa's most common and widely distributed member of the sunfish family and can be found in nearly all waters throughout the state. The Bluegill is extremely abundant in the backwater and sloughs of the Mississippi River. Although it has been documented throughout the Little Sioux River watershed as well as in the Missouri River, the Bluegill is not common in western Iowa streams.
Aside from farm ponds and impoundments, the largest populations of Bluegill are in warm pools and backwaters of low-gradient streams, and particularly in overflow pools along floodplains with some aquatic vegetation or other cover. Researchers note that stream populations may be sustained by continuous escapement from impoundments. The Bluegill is intolerant of continuous high-turbidity, siltation and flowing waters, although in Wisconsin, bluegill were often found in moderately swift waters of streams.
Bluegills consume zooplankton when young, but switch to aquatic insects after they mature. The small-sized mouth of this fish limits the size of food particles ingested and almost dictates a diet of insects and similar small organisms. While insects remain the staple food item for adults, crayfish, snails small fish and fish eggs are also consumed. Algae and other vegetation are eaten when normal food items are scarce. Fish lice, Argulus, have been identified in bluegill stomach contents, indicating that these fish may perform a "cleaning" function on heavily parasitized fish.
Bluegill reproduce over a wide time period, usually from late May to early August in Iowa, but peak spawning occurs in early June. Water temperatures during the spawning season are 70 to 80 degrees F. Males construct nests in water from 1 to 4 feet in depth along the shoreline, over diverse substrate materials, but sand and gravel are preferred. The nests are saucer-shaped depressions about 1 to 2 feet in diameter. From the shore, the colony of nests resembles "elephant tracks". The pugnacious males often build nests, almost touching adjoining nests. It is quite common to find as many as 50 nests in a 75-foot radius. Most nests are only 2 to 3 inches deep, and the male fish keep them fanned free of silt.
After nest construction, the ripe male selects a gravid female and entices her toward the nest with aggressive nudges and bites. Few females lay all their eggs in one nest, so each nest contains the eggs of several females. The males zealously guard the nest from all intruders and keep the eggs free from silt. Sometimes Bluegill hybridize with other members of the sunfish family, Redear Sunfish, Green Sunfish and Pumpkinseed. Males make grunting noises during spawning and may be attracted to spawning areas by odor. Finer substrates produce the most fry per nest with an average of about 64,000 on sand and fine gravel.
Growth of Bluegill varies widely with population density. High population density retards growth while the opposite occurs with low density. Bluegill will reach 1 to 2 inches in length on the average in their first year of life. Most bluegill in Iowa attain lengths of 3.5, 4.5, and 6 inches in their second, third, and fourth year of life. Bluegills mature during the second year under suitable conditions, but slower growth will delay maturity to the third year. Bluegill attain a length of up to 12 inches and weigh up to 2 pounds, but most bluegill caught by anglers seldom exceed 8 inches. The Iowa record Bluegill was 12 7/8 inches long, weighed 3 pounds, 2 ounces and was caught in a farm pond.
The bluegill is the most commonly caught, and one of the most highly sought after, species in Iowa, these fish are extremely important to anglers. Recent stream sampling information is available from Iowa DNR's biological monitoring and assessment program.
Harlan, J.R., E.B. Speaker, and J. Mayhew. 1987. Iowa fish and fishing. Iowa Conservation Commission, Des Moines, Iowa. 323pp.
Loan-Wilsey, A. K., C. L. Pierce, K. L. Kane, P. D. Brown and R. L. McNeely. 2005. The Iowa Aquatic Gap Analysis Project Final Report. Iowa Cooperative Fish and Wildlife Research Unit, Iowa State University, Ames
Illustration by Maynard Reece, from Iowa Fish and Fishing.