Redear sunfish have laterally compressed bodies that are green, grey, or black. They can be distinguished from other sunfish by 3 different characteristics: 1) the red or orange edge on the gill flap, 2) cheeks without orange and blue streaks, and 3) pectoral fins that are greater than a third of the length typically found in sunfish. They often have small green specks on their heads and grey or black specks covering their bodies. Their pectoral fins have 13 to 14 pectoral rays, which taper to a terminal point. Their dorsal fin has 10 to 11 spines, and the anal fin has 3 spines. The terminal end of the gill flap is marked by a large black spot, accompanied by two smaller white spots. The brightly colored terminal edge on the gill flap is red in males and orange in females. Adults measure approximately 224 mm and can weigh as much as 454 g.
Redear sunfish are similar in appearance to their close relative, pumpkinseed sunfish. As a result, the two species are often confused for one another. However, pumpkinseed sunfish have a number of wavy iridescent lines along the check and gill flap that are not present in redear sunfish. (Jenkins and Burkhead, 1993; Page and Burr, 1991; Ross and Brenneman, 2001; Twomey, et al., 1984)
Redear sunfish are native to the central and southern United States and can be found in the St. Lawrence-Great Lakes and Mississippi River drainages, as well as the Atlantic and Gulf Slope drainages. Redear sunfish have been introduced as game fish throughout the United States, as well as in Morocco, South Africa, Panama, and Puerto Rico. Redear sunfish have been introduced to Michigan and may be found in southern rivers as well as Lake Michigan and Lake Erie. (Fuller and Jacobs, 2007; Moyle, 2002; Page and Burr, 1991; Whittier and Hartel, 1997)
Redear sunfish prefer warm and calm or stagnant waters. As a result, preferred habitat is restricted to ponds, lakes, river backwaters, and reservoirs. The river habitats in which they are found tend to be large and slow flowing with moderate amounts of aquatic vegetation. Redear sunfish are mainly found in water that is at least 2 m deep. They commonly live in waters with low salt content, but are considered a freshwater fish. (State of California, 2004; Twomey, et al., 1984)
Optimal incubation temperatures for redear sunfish eggs range from 22°C to 24°C. Incubation normally lasts 50 hours. After hatching, fry (baby fish) hide in gravel nests until for about three days. Juveniles stay close to aquatic plants for protection and at 1 year old, leave the protective cover of aquatic plants to prey on open-water snails.
Growth rates appear to be dependent on turbidity as redear sunfish grow more rapidly in less rough water. Different age classes can be identified according to size. First year fish range from 50 to 100 mm in total length (TL), and second year fish range from 110 to 140 mm TL. Fish that are 5 to 6 years old range from 200 to 250 mm TL. Like most fish, redear sunfish continue to grow throughout their entire lives. (Moyle, 2002; Simon and Wallus, 2008; State of California, 2004; Trautman, 1981)
During mating season, male redear sunfish make popping sounds while close to females, which are used to gain the attention of potential mates. During courtship, males repeatedly swim toward potential mates while making popping sounds, which are made by clapping the jaws shut. Males also gain the attention of females via chemical and visual cues.
Male redear sunfish construct nests made from sand, gravel, and mud. Nests are typically found near aquatic plants, which provide cover for the young fish after they hatch. Nests are approximately 25 to 61 cm wide and occur anywhere from 1 to 6 m underwater. After fertilization, males do not leave the nest until all their eggs have hatched. Female sunfish lay their eggs in several nests each mating period. (Gerald, 1971; Gothreaux, 2008; Schloemer, 1947; Simon and Wallus, 2008; State of California, 2004; Twomey, et al., 1984)
Redear sunfish mate once per year. The start of spawning season depends on water temperature, with warmer temperatures resulting in earlier spawning. Spawning typically occurs in shallow water at temperatures between 21°C and 24°C. Spawning begins in early spring and ends in mid-summer but may extend into early October in warmer climates. Maturation rates are also dependent on climate, as individuals start to spawn at 1 year old in warmer climates and at 2 years old in colder climates. Female sunfish produce between 9,000 and 80,000 eggs per mating season. Eggs hatch 50 hours after being laid. (Gerald, 1971; Gothreaux, 2008; Moyle, 2002; Schloemer, 1947; Simon and Wallus, 2008; State of California, 2004; Twomey, et al., 1984)
Male redear sunfish build nests prior to spawning and protect their nest for up to 3 days after spawning. Females do not give parental care after laying her eggs. (Gothreaux, 2008; Ross and Brenneman, 2001; Schloemer, 1947; Simon and Wallus, 2008)
Redear sunfish have an average lifespan of 6 years. The oldest wild-caught redear sunfish was 8 years old at time of capture. In captivity they can live to be 7 years old. (Schloemer, 1947; State of California, 2004; Twomey, et al., 1984)
Redear sunfish that share habitat with largemouth bass and bluegill must compete for food as fry and juveniles. They eat insect larvae until their jaws are strong enough to crush the shells of their primary prey, aquatic snails. Once their jaws are strong enough, competition for food decreases due to an abundance of snails. Redear sunfish are most active during dawn and dusk and tend to rest during the day. (Gothreaux, 2008; Moyle, 2002; Page and Burr, 1991; Wang, 1986)
Little is known about the home range of redear sunfish. However, their close relatives, bluegill and pumpkinseed sunfish, have home ranges of about 0.5 ha and 1 ha, respectively. (Gothreaux, 2008; Moyle, 2002; Wang, 1986)
Redear sunfish use several modes of communication. It has been suggested that fish of the Lepomis genus use chemical cues during nest building. During spawning, redear sunfish swim in a circular pattern around their mates. Males produce a popping sound to induce egg laying in females, which they produce by clapping the jaws shut. Finally, females select mates, at least in part, based on the pattern and intensity of a potential mate's coloration. (Schloemer, 1947; Simon and Wallus, 2008)
Redear sunfish are mainly bottom feeders. Fry stay in deep waters and feed on algae and microcrustaceans. Juveniles eat insects, insect larvae, and small snails. Once their jaws fully develop, usually at about 1 year old, they begin to feed exclusively on snails. Adults feed on snails, aquatic insects, copepods, and organisms with hard shells, such as crustaceans. Evidence suggests that redear sunfish prefer snails with moderate shell thickness, as opposed to thin or thick shelled snails. (State of California, 2004; Stauffer, et al., 1995; Stein, et al., 1984; Trautman, 1981; Twomey, et al., 1984; Whittier and Hartel, 1997)
Redear sunfish have several predators, including humans. They are considered a sport-fish species and are stocked in many lakes and streams. Humans commonly consume them and their larvae are prey to many other sport-fish species, including largemouth bass and catfish. Redear sunfish avoid predation by retreating to shaded areas and deeper waters. Redear sunfish carcasses are often scavenged by birds and raccoons. Their brownish coloration blends in well with their river-bottom surroundings and helps to camouflage them and avoid predators. (Gothreaux, 2008; Ross and Brenneman, 2001; Stein, et al., 1984; Trautman, 1981)
Introduced redear sunfish have significantly impacted native fish populations. For example, when introduced into habitats occupied by pumpkinseed sunfish, pumpkinseed populations significantly declined. Redear sunfish have strong jaws, which allow them to crack mollusk shells more easily than pumpkinseed sunfish can. As a result, redear sunfish likely decrease food availability for pumpkinseeds.
Redear sunfish are host to the non-native parasitic copepod, Neoergasilus japonicus. A copepod is a tiny crustacean. Neoergasilus japonicus attaches to the outer surface of its host, likely feeding on the tissue underlying the scales. However, the primary diet of free-swimming N. japonicus consists primarily of blue-green algae. (Fuller and Jacobs, 2007; Hudson and Bowen, 2002)
There are no known adverse effects of redear sunfish on humans. However, when redear sunfish populations are introduced to non-native waters, they may negatively affect the ecosystem and out-compete native fish species. This may affect the fishing industry and overall health of ecosystems that humans depend on for food and water.
Redear sunfish population numbers are stable throughout its range and are in no danger of decline. Since humans are introducing these fish to new habitats, populations could increase as their range spreads. (Gothreaux, 2008; Ross and Brenneman, 2001)
Jacob Barbee (author), Radford University, Karen Powers (editor), Radford University, John Berini (editor), Animal Diversity Web Staff, Tanya Dewey (editor), University of Michigan-Ann Arbor, Renee Mulcrone (editor), Special Projects, Rachelle Sterling (editor), Special Projects.
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