Lepomis microlophus

Invasion History

First Non-native North American Tidal Record: 1956
First Non-native West Coast Tidal Record: 1956
First Non-native East/Gulf Coast Tidal Record: 1973

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General Invasion History:

Redear Sunfish (Lepomis microlophus) is native to the Mississippi and Gulf Slope drainages from Iowa and Indiana to the Nueces River, Texas (Page and Burr 1991). Its native Atlantic Slope range is less clear, and may have ended near the Florida-Georgia border, or as far north as the Cape Fear River (Smith 1907; Fuller et al. 1999). Redear Sunfish have been widely stocked in ponds and impoundments, largely by individuals and state agencies. Redear Sunfish have been introduced to river systems in 28 states, including the Great Lakes Basin, and the San Francisco Bay Delta, the Pamlico Sound and Chesapeake estuaries (Cohen and Carlton 1995; Mills et al. 1993; USGS Nonindigenous Aquatic Species Program 2018). In its native range, L. microlophus commonly occurs in brackish estuaries (Peterson 1988; Peterson and Meador 1994). In invaded areas in the San Francisco Delta and Chesapeake Bay, it is known primarily from tidal freshwater areas (Lippson et al. 1979; Cohen and Carlton 1995: Feyrer et al. 2003; Kraus et al. 2012), but could extend its habitat range in the future.

North American Invasion History:

Invasion History on the West Coast:

Redear Sunfish were first found in California in the Colorado River in 1951, resulting from stocking in the Colorado River. The fish was deliberately stocked in southern California reservoirs in 1954, as a potential forage fish for Largemouth Bass (Micropterus salmoides, believed to be less prone to stunting than Bluegills (L. macrochirus). In 1955, Redear Sunfish were transferred to the Central Valley Hatchery, and soon planted in many private ponds in the valley. They were present in reservoirs and ponds in the San Francisco Bay watershed in the 1960s and 1970s, and collected in several tributaries in the 1980s (Coyote Creek, the Guadalupe River, and Sanchez Creek) (Wang 1986; Leidy 2007). In the 1980s and 1990s, Redear Sunfish were the second to fourth most abundant fish species in the freshwater Delta, behind Bluegill, Threadfin Shad, White Catfish, Mississippi Silverside (Feyrer and Healey 2003; Brown and Michniuk 2007; Grimaldo et al. 2012), and generally increasing over time. Two specimens were caught in the brackish Suisun marshes (Matern et al. 2001).

Invasion History on the East Coast:

Redear Sunfish were apparently not among the 'bream' or 'sun-fish' introduced by the U.S. Fish Commission, but were introduced later by state agencies, fishermen, or pond-owners, as indicated by dates of first record (late 1950s, South Carolina (Poole 1978); 1958, Virginia; Jenkins and Burkhead 1993; 1964, North Carolina, USGS Nonindigenous Aquatic Species Program 2018). Jenkins and Burkhead (1993) indicated that the distribution of this species was undersampled, because of its widespread introduction in farm-ponds. Redear Sunfish are known from North Carolina estuarine tributaries in the Cape Fear River, Bogue Sound, the Neuse and Pamlico Rivers, and Currituck Sound. The range of this fish has expanded greatly since the 1970s, when it was mostly limited to farm ponds (Menhennick et al. 1974; Menhennick 1991; USGS Nonindigenous Aquatic Species Program 2018).

In the Chesapeake Bay watershed, it was first reported from the Potomac drainage in 1958, probably collected in a stream after escaping from a stocked pond (Jenkins and Burkhead 1993). In 1956–1974, it was collected off Indian Head and Blossom Point in the fresh-oligohaline region of the tidal Potomac River (O'Dell et al. 1976). First records in other tributary basins were 1967 in the James, 1971 in the York, and 1977 in the Rappahannock (Jenkins and Burkhead 1993). The Virginia Institute of Marine Sciences Striped Bass Survey captured specimens in the tidal James, Rappahannock, and York Rivers. Abundances were low (39 fish) compared to native Pumpkinseed L. gibbosus (1731), Redbreast Sunfish L. auritus (739), and introduced Bluegill L. macrochirus (700) (Virginia Institute of Marine Sciences 1998). From 1971 to 1973 Redear Sunfish have been stocked in the Pennsylvania drainage of the Susquehanna River (Denoncourt et al. 1975b), but were not recorded below Conowingo Dam (McKeown 1984).

In 1994, a population of Redear Sunfish was found in Wagamons Pond (Sussex County DE). In 1996, this species was collected in Trap Pond (Sussex County) and the St. Jones River (Kent County) (Raasch 1996).

Redear Sunfish were first introduced to the Great Lakes basin in 1928 in lakes and ponds in Indiana. It has been introduced into many lakes in the basin, but is not established in the Great Lakes proper (Emery 1985; Mills et al. 1993).

Invasion History Elsewhere in the World:

Redear sunfish were first introduced to Puerto Rico in 1948 and became widely introduced in reservoir on the island (USGS Nonindigenous Aquatic Species Program 2018). They were introduced as a forage fish for Largemouth Bass and as biocontrol of the snail Biomphalaria glabrata, which hosts the blood fluke Schistosoma mansoni (Lever 1996). It is also established outside its native range in Mexico and in one lake in Morocco. It may also be established in South Africa, Panama, and Mauritius, but sources are conflicting (Lever 1996; Froese and Paul 2018).

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Description

The Redear Sunfish (Lepomis microlophus) is a medium-sized freshwater fish. Fishes of the genus Centrarchidae (Sunfishes and Black Basses) have a strongly laterally compressed body. They have a spiny and a soft dorsal fin, which are fused. They have 3–8 anal spines, thoracic pelvic fins, and ctenoid scales. The sunfishes of the genus Lepomis have a shallowly forked tail, a smooth edge to the gill cover, and a fleshy 'ear-flap' projecting from the gill-cover. The gill-cover has a thin, flexible rear edge. Redear Sunfish have a deep, strongly compressed, oval body, a pointed snout, a small terminal mouth (not extending to the pupil of the eye), and long, pointed pectoral fins, which extend far past the eye when bent forward. The dorsal fin has 10–11 spines and 10–12 rays, while the anal fin has 3 spines and 9–11 rays. There are 34–47 lateral line scales. The maximum length is 269 mm, but a more usual length is 135–216 mm. The back is olive, with a golden sheen. The belly is white to yellow. Juveniles have dusky gray bars, while adults are marked with dusky spots. The ear-flap is black, with a bright orange-red spots, and a white margin. Breeding males are brassy-gold with dusky pelvic fins (Hardy 1978; Page and Burr 1991; Jenkins and Burkhead 1993; Moyle 2002).

In the southeastern US, a frequent common name is 'Shellcracker', because of this fish's habit of feeding on mollusks (Moyle 2002).

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Taxonomy

Ecology

General:

The Redear Sunfish (Lepomis microlophus) is a medium-sized freshwater fish, which also enters brackish water. Adults mature at 8 months (Puerto Rico), 1–2 years in Tennessee, and (possibly) 3–4 years in California, at a size of 88 (North Carolina) or 130-180 mm (California) (Hardy 1978; Moyle 2002). Spawning takes place at 22–32 °C, in freshwater (Hardy 1978; Wang 1986; Jenkins and Burkhead 1993; Moyle 2002). Males excavate and guard a nesting site in shallow water, in sand or gravel, often nesting colonially, but guarding their nests individually. Males may spawn with several females, and guard the nests until they hatch. In one study, female fish had 64,000 eggs (Froese and Pauly 2018). Eggs hatch in 1–3 days at 21–29 °C. When the yolk-sac is absorbed, the larvae leave the nest and begin feeding on zooplankton (Hardy 1978; Jenkins and Burkhead 1994; Moyle 2002). Redear Sunfish are less considered prone to early maturation and stunting than Bluegill Sunfish (Moyle 2002).

Redear Sunfish have been collected at temperatures up to 34 °C (Hardy 1978). The lower temperature has not been reported. Based on its northern range limits (to southern Illinois, Indiana, Maryland, Page and Burr1991) it probably tolerates temperatures range as low as 4 or 5 °C, but may not survive very long winters. In estuaries in the southern US, it frequently ranges into brackish water at salinities up to 10–12 PSU, and has been reported from salinities up to 20 PSU (Hardy 1978; Peterson 1988). Reported habitats include swamps, lakes, vegetated pools with mud or sand bottoms, small to medium rivers, lagoons, and bayous (Hardy 1978; Page and Burr 1991). Adults prefer deeper water than most other sunfish, below 2 m. They often feed by biting the substrate, crushing their prey, and ejecting gravel and hard parts. Young Redear Sunfish are planktivores, while adults shift to aquatic insects larvae, and amphipods, and especially, snails, which they are able to crush with specially adapted molariform teeth (Jenkins and Burkhead 1994; Winwright 1996 Fisher Huckins 1997; Moyle 2002). Common predators include larger fishes, such as bass and catfish, birds, and humans (Moyle 1997).

Food:

Mollusks, other invertebrates

Consumers:

Fishes

Competitors:

Other sunfishes

Trophic Status:

Carnivore

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Habitats

General Habitat	Fresh (nontidal) Marsh	None
General Habitat	Grass Bed	None
General Habitat	Coarse Woody Debris	None
General Habitat	Swamp	None
General Habitat	Nontidal Freshwater	None
General Habitat	Tidal Fresh Marsh	None
General Habitat	Salt-brackish marsh	None
General Habitat	Unstructured Bottom	None
Salinity Range	Limnetic	0-0.5 PSU
Salinity Range	Oligohaline	0.5-5 PSU
Salinity Range	Mesohaline	5-18 PSU
Tidal Range	Subtidal	None
Vertical Habitat	Nektonic	None

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Life History

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Tolerances and Life History Parameters

Minimum Temperature (ºC)	5	Based on geographical range (Page and Burr 1991)
Maximum Temperature (ºC)	34	Hardy 1978
Minimum Salinity (‰)	0	This is a freshwater species.
Maximum Salinity (‰)	20	The maximum salinity given here, 20 PSU was a field record from Mississippi. This salinity seems high for a freshwater fish. There are numerous records from 10-12 PSU (Hardy 1978; Peterson 1988).
Minimum Length (mm)	88	Size at first maturity (Hardy 1978)
Maximum Length (mm)	269	a more usual length is 135-216 m

General Impacts

Redear Sunfish (Lepomis microlophus) are a popular pan-fish and are believed to be less prone to overpopulation and stunting than Bluegills (Dill and Cordone 1997; Jenkins and Burkhead 1993; Moyle 2002). This fish has sometimes been introduced for biocontrol of pest populations of snails in lakes (Carlander 1977). In Puerto Rico, the Redear Sunfish was found to be useful for the biocontrol of the snail Biomphalaria glabrata, a host of the blood fluke Schistosoma mansoni (Lever 1996).

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References

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