Members of the sunfish family are flattened, brightly colored, ‘pan-fish’. The most unique feature of longear sunfish is their elongated gill cover, or opercular flap, giving an appearance of a ‘long ear’. They are relatively small sunfish with individuals are usually 71 to 94 mm in length, although one 240 mm fish was found in Michigan. Females are generally slightly smaller than males. Mature males are generally brighter and have a more pronounced opercular flap than females, up to 230 mm long.
Longear sunfish are greenish to rusty brown on the back, with lighter colored sides and yellow to orange-red bellies. They have bright specks of blue, green, yellow, and orange along the back and sides. Their cheeks are orange with wavy blue streaks near their mouths and eyes. The opercular flap is black and bordered with light red to yellow. Males who are breeding become bright iridescent green on the back and bright orange on the belly, and the fins turn a deep rusty orange color.
Longear sunfish are only found in North America, primarily in the Mississippi and Great Lakes watersheds. The species ranges from Minnesota east to Ontario, Ohio, and western Pennsylvania southward through the Mississippi Basin to the Gulf states of Mexico and east to the Apalachiocola River.
Longear sunfish, like other members of the sunfish family, are freshwater fishes. In the warmer months of spawning season longear sunfish are generally found in shallower, warmer waters near the sources of streams which have pools with a flowing current. They prefer streams with a hard bottom of clay or gravel with clear waters and they usually stay in or near aquatic plants. Although more abundant near the sources of streams, they can be found in streams and rivers of all sizes and are also found in lakes. Compared to other members of the sunfish family, longear sunfish are better at getting food in moving waters than still waters. This may explain why longear sunfish are more abundant in streams than lakes compared to other members of the family. They cannot tolerate cloudy water. Throughout the 20th century their populations have been reduced in areas where their native streams have suffered increased cloudiness.
The number of young that successfully hatch may range from 52 to 1,132. In nature, the eggs hatch in 3 to 5 days, in an aquarium they can hatch in 2 days. Swimming up to the water surface and feeding can begin 7 days after hatching in an aquarium.
Female longear sunfish prefer male longears with longer opercular flaps. When a breeding female enters a nesting colony, a male longear sunfish will attempt to lead her to its nest. Leading involves behavior where the male spreads its fins, swims directly toward the female and then returns directly to his nest. If a female follows the male to his nest, they begin a circular spiral of the nest with the female always toward the center. Several spawning events will occur and then the female is chased from the nest. In one study, the total number of eggs laid in a nest varied from about 137 to 2,836 eggs.
Immediately after the female leaves, the male begins to fan the nest with his fins. He then swims vertically over the nest and fans with his tail. The fanning is strong enough to move small pebbles. He will fan the nest up to an hour after the spawning event. This behavior may help mix the eggs and sperm and help drive the eggs deep into the gravel. The female, after being chased from the nest, will enter the nests of other males for additional spawning events.
Longear sunfish nest in colonies, although in some populations individuals will build solitary nests. Colony size and the distance between the nests vary. In crowded conditions the colonies can be quite large with the nests so close together their rims almost touch. In dense conditions the male fish only defends the nest itself. In less dense conditions, the nests are further apart and the male will guard a territory slightly larger than the nest.
Male longear sunfish build the nest without aid from the female. In late spring or early summer, males move into relatively shallow water (20 to 60 cm deep) and establish territories in which they build nests. They prefer to nest in gravel if available; otherwise, they will build in sand or hard mud. The nest is created by the powerful sweeping of the male’s tail (called tail-wags) across the bottom while the fish swims at a 45° angle to the gravel. This action results in a circular depression that is about 35 to 45 cm in diameter, 3 to 7 cm deep, with rims 7 to 9 cm wide. Water temperatures in the nest area are relatively warm and vary from approximately from 23° to 31° C. They will reoccupy nests abandoned by other sunfish.
Male longear sunfish also have an interesting alternative reproductive strategy to nest building. Some males are sneakers. The sneaker male is generally younger and less colorful than a nest building (dominant) male. The sneaker male mimics the appearance of a female longear sunfish. The sneaker will hide near an active nest and dash into the nest and release sperm while the dominant male is spawning with a female. The satellite male is similar in age and appearance to the sneaker male, but instead of dashing into the nest, he will hover over a nest, acting like a non-threatening female, and slowly swim down into the nest containing a breeding pair of sunfish and, like the sneaker, release sperm during the spawning event. Male longear sunfish that build solitary nests have better success defending their nests from sneaker and satellite males than males with nests in colonies.
Male longear sunfish guard their nest territories during all phases of reproduction. They will continuously chase both their own and other species out of their nesting territories. Males will continue to guard their nests even after all the young have left.
Most longear sunfish do not live beyond four years, although one individual found in the wild in Michigan was nine years old.
In general, longear sunfish are active during the day and inactive at night, although they have been observed to feed at the surface under bright moonlight during the summer. These fish are less active during the mornings and evenings and spend this time in darker waters and/or closer to cover. This may be to avoid predators, or a preference to move about and feed during the warmer part of the day.
Non-nesting longear sunfish are social and are found with other longears and other types of fishes, the species of which vary by location.
Larger longear sunfish are dominant over smaller longear regardless of gender. In the wild, dominance behavior is made up of displays and chasings but little physical contact. In an aquarium, longear sunfish interact very aggressively with other longear sunfish. If two longear sunfish are placed together in a 5 gallon tank the larger fish will become dominant and will chase and nip the subordinate fish until the subordinate fish dies. If placed in a large enough tank, longear sunfish can co-exist in an aquarium.
During the spawning season a longear sunfish’s home range is relatively small and well-defined. Individuals occupy an area of 30 m to 60 m of a particular stream. If moved from their home range, they will quickly return, apparently through the use of smell. During the winter larger individuals move away to deeper waters downstream. Although many do, individual fish do not necessarily return to the same spawning waters each year.
Longear sunfish appear to desert their spawning home range in winter.
Longear sunfish have a number of behavioral display postures that are probably used in communication such as when the male the turns on his side and displays his bright orange belly, when he turns toward another fish and lifts up his gill covers, biting, courtship circling, and so on. Male longear sunfish are also known to make a distinctive grunting sound during courtship and spawning.
Longear sunfish feed nearer to the surface than other sunfish. They mostly eat aquatic insects, small crustaceans, fish eggs (including those of its own species), young bass, and young sunfish. They have been observed eating dragonflies and other insects, which touch the surface of the water. Other foods include detritus, gnat larvae, day flies, snails and leeches.
Longear sunfish have also been seen following northern hognose suckers. As a northern hognose sucker moves along the bottom shoving pebbles around and picking them up with its mouth, longear sunfish will move along beside the sucker, picking around and feeding in the gravel after the sucker stirs it up.
In nature, longear sunfish have been seen to hide in aquatic plants near hard structures (like stumps or woody debris) or in otherwise shaded areas to avoid predation. They also will dart into deeper waters when threatened. Predators of longear sunfish, like largemouth bass and wading birds hunt using their sight and the brightly colored longear sunfish probably benefits by hiding where it is less likely to be spotted. Adult longear sunfish have been shown to occupy deeper, and thus darker, waters in the mornings and evenings when large predators are most active. Spawning occurs in shallow waters. The shallowness of the waters may give longear sunfish nests and eggs some protection from larger aquatic predators.
Sunfish are an important link in the food chain. They act as both predator and prey.
Longear sunfish cause no known negative economic impact.
Longear sunfish have little economic importance. They are too small to be considered a food fish for humans. Fisherman generally throw them back due to their small size. The species has been successfully bred in captivity, and may be kept as pets and used for laboratory experiments.
Longear sunfish are not listed federally or internationally as threatened or endangered. The species is listed as threatened (since 1979) by the state of Wisconsin. The species is not listed as threatened or endangered in any other state or province within its native range.
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