From Ohio History Central
Bluegills (Lepomis macrochirus) are members of the sunfish family. They have a small mouth, a high dorsal fin with a black dot, and a long, pointed pectoral fin. It also has five to nine vertical bars on its olive-colored sides and back.
Typical bluegill habitat is inland lakes, ponds, reservoirs and slow-moving streams with clear water a lot of water plants. Bluegills spawn between May and August, with peak spawning in June. Spawning nests are scooped out by the male's tail and can be found in water that is from one to four feet deep. Bluegills may interbreed with other sunfish including warmouth, green, longear and pumpkinseed. Once the 10,000 - 60,000 eggs are laid, males will vigorously defend them. Small bluegills will often nest together in large numbers. The young fry hatch in five days.
Upon maturity, bluegills will reach an average of seven to ten inches and feed primarily on aquatic insects, including midge fly larvae; pond weeds, fish eggs; caddis fly worms and damsel fly nymphs
They are very popular with fishermen of all ages. They are almost always willing to "bite" at any bait and, although they are small, put up a good fight. They are also used as bait themselves for larger fish such as the channel catfish and the largemouth bass.
The Ohio record bluegill was caught in Salt Fork Lake and was recorded at 3.28 pounds and 12.75 inches long on April 28, 1990.
Bluegills have always been abundant in Ohio. In the mid- to late 19th century, it was an important commercial food fish from Port Clinton and Toledo to Buckeye, Indian and St. Marys lakes. During peak season, dozens of barrels of bluegills were shipped weekly from these lakes.
Before 1900, it could be found throughout glaciated Ohio and it soon could be found in the canal systems. Ohio's canals were beneficial in distributing the bluegill throughout the state. Between 1920 - 1950 the state stocked farm ponds and other waters with millions of bluegills.
In areas such as Lake St. Marys, as waters became clouded and stumps and water plants disappeared, bluegill populations declined until only a small number could be found in the lake by 1940. These same changes in water conditions in other areas of the state caused adult bluegills to become stunted, many reaching a length of less than 4 inches. Another reason for smaller sized bluegills is periods of large population explosions caused by the disappearance from over-fishing of its natural predator, the largemouth bass. Despite these minor concerns, bluegills are found throughout Ohio and are still the species of fish most often caught by people of all ages.