Sunfish biology and identification
The bluegill is Minnesota's largest and most popular sunfish. It is found in about 65 percent of the state's lakes and many of its slow streams, including the backwaters of the Mississippi. It is rare in the Lake Superior drainage.
Appearance varies considerably among individuals, as is true with most sunfish. Most bluegill are light to dark olive, though older fish may have a purplish tinge. Cheeks and gill covers are often bluish and the ear flap is black. The rearward edge of the soft portion of the dorsal fin carries a dark blotch. Breeding males are marked by bright blue and orange. Females and younger fish are less colorful and are often marked by dark vertical bars on their olive backs. Though they occasionally exceed a pound, an 8-inch bluegill is considered large.
the bluegill spawns from late May or through much of the summer in water temperatures of 67 to 80 degrees. The male fans out a nest in firm-bottomed shallows, often within a colony of dozens of other nests. A single female can deposit more than 50,000 eggs. The male then guards eggs and fry.
The bluegill's mouth is small; it feeds mostly on aquatic insects and other small invertebrates. Young bluegill will feed in heavy weeds to avoid predators. Bluegill large enough to be of no interest to bass often swim freely in more open water, feeding heavily on tiny drifting zooplankton. This open-water feeding is especially common if bluegill must compete with pumpkinseed and green sunfish, which stay in the weeds. When food is scarce, bluegill will eat their own eggs.
Like the bluegill, the pumpkinseed lives in many of Minnesota's lakes and streams. This popular sunfish is nearly as large as the bluegill. The pumpkinseed can be distinguished from the bluegill by the bright orange spot at the tip of the ear flap and the lack of a dark blotch on the soft portion of the dorsal. Breeding males are particularly colorful; their cheeks and gill covers are marked by wavy bright blue bars. Identifying and distinguishing sunfish is complicated by frequent hybridization.
The pumpkinseed spawns from May until well into the summer, nesting in colonies and defending its nests, much as bluegill do. In fact, pumpkinseed sometimes build nests in bluegill colonies. The pumpkinseed eats aquatic insects and other invertebrates. It uses its specially adapted teeth to feed heavily on snails.
Drab in comparison to others of this tribe, the green sunfish is also distinguished by a mouth far larger than is typical of other sunfish. The ear lobe is black with a pale margin. The green sunfish is common in many lakes throughout the state and thrives in creeks. It tolerates greater turbidity and lower dissolved oxygen than bluegill or pumpkinseed.
The green sunfish usually is far smaller than pumpkinseed or bluegill, though hybridization with the larger species produces larger fish. Spawning times and habits are similar to those of other sunfish.
Like the bluegill, the green sunfish eats aquatic insects and other invertebrates and small fish. Because of its larger mouth, the green sunfish may eat larger critters than a bluegill of equal size, thus reducing competition between the species.
The orangespotted is the smallest Minnesota sunfish, rarely reaching 4 inches. It is on of our most colorful species. Spawning males carry orange-red lines of the cheeks and gill covers. Their bellies and lower fins are reddish. Ear lobes are dark with a pale border. Spawning habits are similar to those of other sunfish. Found in southern Minnesota, the orangespotted sunfish is too small to be popular with anglers. It is more tolerant of pollution and turbidity than other sunfish. Declines in water quality enable the orangespotted sunfish to extend its range while more desirable sunfish decline.