Bluegill

The bluegill is noted for the large black appendage (the "ear") on each side of the posterior edge of the gill covers as well as the base of the dorsal fin. The sides of its head and chin are commonly a dark shade of blue, hence the name "bluegill". The precise coloration will vary due to the presence of neurally controlled chromatophores under the skin. The fish usually displays 5–9 vertical bars on the sides of its body immediately after being caught as part of its threat display. It typically has a yellowish breast and abdomen, with the breast of the breeding male being a bright orange. The bluegill has three anal fin spines, ten to 12 anal fin rays, six to 13 dorsal fin spines, 11 to 12 dorsal rays, and 12 to 13 pectoral rays. They are characterized by their deep, flattened bodies. They have a terminal mouth, ctenoid scales, and a lateral line that is arched upward anteriorly. The bluegill typically ranges in size from about 4 to 12 inches (100–300 mm), and reaches a maximum size just over 16 inches (410 mm). The largest bluegill ever caught was 4 lb 12 oz (2.2 kg) in 1950. The bluegill is most closely related to the orangespotted sunfish and the redear sunfish, but differ in having a dark blotch at the rear of the dorsal fin. The blotch is present in most adult fish, and absent in young juveniles. A few other sunfish species may also have a blotch in that area. …

The bluegill occurs naturally in the United States east of the Rocky Mountains from coastal Virginia to Florida, west to Texas and northern Mexico, and north to western Minnesota, New York and southeastern Ontario. They have been introduced widely in North America and Europe, South Africa, Zimbabwe, Asia, South America, and Oceania. Bluegills have also been found in the Chesapeake Bay, indicating they can tolerate up to 1.8% salinity. In some locations where they have been transplanted, they are considered pests: trade in the species is prohibited in Germany and Japan. In the case of Japan, bluegills were presented to the then-crown prince, Akihito, in 1960 as a gift by Richard J. Daley, mayor of Chicago. The prince, in turn, donated the fish to fishery research agencies in Japan, from which they escaped and became an invasive species that wreaked havoc with native species, especially in Lake Biwa. Akihito has since apologized. Bluegill live in the shallow waters of many lakes and ponds, along with streams, creeks, and rivers. They prefer water with many aquatic plants, and seclude themselves within or near fallen logs, water weeds or any other structure (natural or manmade) that is under water. They can often be found around weed beds, where they search for food or spawn. …

Young bluegills' diet consists of rotifers, copepods, water fleas, and insects (mainly chironomids). The adult diet consists of aquatic insect larvae (mayflies, caddisflies, dragonflies), but can also include terrestrial insects, zooplankton, shrimp, crayfish, leeches, other worms, snails, and other small fish (such as minnows). If food is scarce, bluegill will also feed on aquatic vegetation and algae, and if scarce enough, will even feed on their own eggs or offspring. As bluegill spend a great deal of time near the surface of water, they can also feed on surface bugs. Most bluegills feed during daylight hours, with a feeding peak being observed in the morning and evening (with the major peak occurring in the evening). Feeding location tends to be a balance between food abundance and predator abundance. Bluegill use gill rakers and bands of small teeth to ingest their food. During summer months, bluegills generally consume 3.2 percent of their body weight each day. To capture prey, bluegills use a suction system in which they accelerate water into their mouth. Prey comes in with this water. Only a limited amount of water is able to be suctioned, so the fish must get within 1.75 centimeters of the prey.