Lepomis gulosus

Invasion History

First Non-native North American Tidal Record: 1897
First Non-native West Coast Tidal Record: 1930
First Non-native East/Gulf Coast Tidal Record: 1897

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General Invasion History:

The Warmouth (Lepomis gulosus) is native to the Great Lakes and Mississippi Basins, from Pennsylvania to Minnesota, south to the Gulf, from Florida to Texas, and Atlantic drainages south of the James River (Jenkins and Burkhead 1993; Lee et al. 1980; Page and Burr 1991). The original range on the Atlantic Coastal Plain is uncertain because of extensive introductions and uncertain early records. It was considered likely native to James and Dismal Swamp, based on Cope's (1869) record, but is probably introduced northward, with some uncertainty due to the lack of early records and spotty present distribution, but is clearly introduced in the Potomac, Susquehanna, Delaware, and Hudson rivers (Jenkins and Burkhead 1993; Horwitz 1986; Daniels et al. 2005). Warmouth were transported and stocked by the US Fisheries Commission and state agencies. On the West coast, it was introduced to the Sacramento-San Joaquin Delta and the Columbia River estuary (Lampman 1946; Dill and Cordone 1997; Moyle 2002). Currently, it has been introduced to non-native waters in 29 states (USGS Nonindigenous Aquatic Species Program 2018). It has also been introduced to Puerto Rico and Mexico (Lever 1996).

North American Invasion History:

Invasion History on the West Coast:

The early history of stocking of the Warmouth on the West Coast is obscure. Early plantings were made in Lake Cuyamaca, San Diego County (400 fish) and the Feather River (100 fish), California, in 1891 and 1895, but details in different reports are contradictory, and it is not clear that any of these fish survived (Smith 1895; Shebley 1917; Dill and Cordone 1997). However, Warmouth were reported to occur in the Central Valley in 1931 and were included in a key for Delta fishes in 1941 (Dill and Cordone 1997). In 1966, Warmouth comprised about 2% of centrarchid fishes collected in the Delta (Turner 1966, cited by Cohen and Carlton 1995). In the freshwater Delta in the 1990s to 2000s, Warmouth were were <1 to 2.2% of the total catch (Feyrer and Healy 2003; Brown and Michniuk 2007; Grimaldo et al. 2012). Single specimens were caught at several stations in the fresh-brackish Suisun Marshes (Matern et al. 2002). Warmouth occur mostly in sloughs of the Delta (Wang 1986).

In the Columbia River basin, there was a stocking of 201 Warmouth in 1892, a release of mixed sunfishes from Illinois in 1893 in the Willamette River at Salem, and a release of mixed Mississippi 'spiny-rayed fishes' displayed at the Lewis and Clark Exposition in Portland in 1905 (Lampman 1946). It is not clear if any of these releases was responsible for the introduction of the Warmouth to the Columbia River system. However, Warmouth were caught in the Columbia River at Kalama in 1930 and in the Willamette River and Columbia Slough near Portland in small numbers (Farr and Ward 1992; Van Dyke et al. 2009).

Invasion History on the East Coast:

Warmouth were collected in the James River near Richmond, Virginia in 1867 (Cope 1869). This fish was probably native in this river, but is introduced in Chesapeake tributaries further north (Jenkins and Burkhead 1993). Warmouth were stocked in Shenandoah River, 1893 (Worth 1895), and was first caught in the Washington DC area in Little River, a Potomac tributary, in 1897. By 1898 it was 'apparently becoming common in a few places' (Smith and Bean 1898). It was collected at Chain Bridge, at the head of tide on the Potomac in 1910 (U.S. National Museum of Natural History 2001). Other tributaries were colonized later, probably by informal stocking. The first verified record of Warmouth in the Rappahannock River was in 1938 (Jenkins and Burkhead 1993), but it was not reported from the tidal river by 1951 (Massman et al. 1952), but was later found there by Maurakis et al. (1987). Warmouth was reported as apparently introduced to the Susquehanna River (Fowler 1919), but was not listed for the river by Denoncourt and Cooper (1975) or Denoncourt et al. (1975b), or for the river below Conowingo Dam by McKeown (1984). However, Aa specimen was caught in Broad Creek, a South River tributary near Annapolis in October 2008 (Rob Aguilar, personal communication).

In the Delaware River, Warmouth was reportedly introduced in the Delaware River (Fowler 1948). Specimens were caught at a power plant in Chester, Pennsylvania River, in 1977 (Horwitz 1986), and in Newcastle County, Delaware County, Augustine Creek (Raasch 1997). In the Hudson River estuary, Warmouth were first collected in 1936, and collected again in the 1970s near Annandale, New York (~River km 160), and near Newburgh (~92 River km) (Smith and Lake 1990), in the tidal freshwater region of the estuary. Daniels et al. (2005) listed the species as 'rare but increasing'. Warmouth may have been introduced as a contaminant with a stocking of Green Sunfish (Greeley 1937, cited by Mills et al. 1997).
 

Invasion History Elsewhere in the World:

Warmouth were introduced to reservoirs in Puerto Rico in 1916, apparently as a contaminant in a stocking of Largemouth Bass (Micropterus salmoides) and Rock Bass (Ambloplites rupestris). The Rock Bass introduction failed, but in 1971, a Warmouth was caught in Carite Reservoir (Lever 1996; USGS Nonindigenous Aquatic Species Program 2018). They also may have been introduced into reservoirs in the Rio Grande basin in northern Mexico, probably south of their native range (Edwards and Contreras 1991; Lever 1996).

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Description

The Warmouth (Lepomis gulosus) is a medium-sized freshwater fish. Fishes of the family 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 stiff rear edge. Warmouth have a compressed, somewhat rectangular 'bass-like' body, a large mouth (with the upper jaw extending beyond the midpoint of the eye), and short, rounded pectoral fins, which do not extend past the eye when bent forward. The dorsal fin has 9–11 spines and 9–11 rays, while the anal fin has 3 spines and 9–10 rays. There are 36–44 lateral line scales. The maximum length is 310 mm, but a more usual length is 100–180 mm. The back and sides are olive-brown, often with a purple sheen and dark-brown mottling, and dark-brown chainlike bars on the sides, with a white-to-yellow belly. The ear-flap is black, with a yellow edge, marked with a small red spot. Dark Brown lines radiate across the head from the bright red eyes (Hardy 1978; Page and Burr 1991; Jenkins and Burkhead 1993; Moyle 2002).

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Taxonomy

Ecology

General:

The Warmouth (Lepomis gulosus) is a freshwater fish characteristic of lakes, ponds, backwaters, swamps, and slow-moving rivers (Page and Burr 1991; Moyle 2002). Spawning males are bright yellow, with iridescent blue streaks on the gill cover (Hardy 1978). The fish mature at ages of 1–2 years, at 75–100 mm (Hardy 1978; Jenkins and Burkhead 1993). Spawning takes place at ~21 °C (Hardy 1978). Males excavate and guard a nesting site, in sand, rubble, or detritus or leaf mold, often near tree roots, stumps, sticks, etc. Males are territorial and aggressive when defending nesting areas. Nesting males tend to be solitary. Females can carry 4500–63,200 eggs (Hardy 1978; Jenkins and Burkhead 1994). Eggs hatch in 25–45 hours at 25–28 °C. Early maturation and stunting is common in crowded populations, resulting in fish that stop growing at 100–120 mm (Moyle 2002).

Warmouth inhabit a wide range of freshwater habitats, mostly in static and slow-moving waters at low elevation and can tolerate a wide range of temperatures, 4–34 °C (Hardy 1978; Page and Burr 1991; Moyle 2002). It has been collected at salinities as high as 17 PSU, but is rare at salinities above 1.5 PSU (Hardy 1978; Peterson 1988; Jenkins and Burkhead 1993). In estuaries, it seems to be found mostly in sloughs on the edges of estuaries, with few records from brackish waters (Wang 1986; Peterson 1988; Van Dyke et al. 2009). As a relatively small fish with a big mouth, Warmouth are opportunistic feeders, feeding small aquatic insects and crustaceans as juveniles, and incorporating larger adult insects, crayfishes, and small fishes as it grows (Jenkins and Burkhead 1994; Moyle 2002). Predators of Warmouth include larger fishes, such as Largemouth Bass, birds, and humans. However, frequent stunting makes this fish a less desirable catch (Moyle 2002).

Food:

insects, snails, crayfish, fishes

Consumers:

fishes, birds, humans

Competitors:

other sunfish species

Trophic Status:

Carnivore

Carn

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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)	4	Based on geography, range includes areas with winter ice cover.
Maximum Temperature (ºC)	34	Hardy 1978
Minimum Salinity (‰)	0	This is a freshwater species.
Maximum Salinity (‰)	17.4	Warmouth are usually found at salinities under 1.5 PSU (Hardy 1978)
Minimum Reproductive Temperature	21.1	Hardy 1978
Minimum Reproductive Salinity	0	This is a freshwater species.
Minimum Length (mm)	75	Minimum for reproduction (Hardy 1978)
Maximum Length (mm)	284	Hardy 1978

General Impacts

The Warmouth Lepomis gulosus) is a popular pan-fish in its native range, but is prone to stunting (Moyle 2002). In introduced estuarine populations on the West and East Coast, it is relatively rare and has few ecological or economic impacts (Cohen and Carlton 1995; Far and Ward 1992; Van Dyke et al. 2009). Hybrids have been noted with Green Sunfish, Bluegills, and Pumpkinseeds (Hubbs 1955; Jenkins and Burkhead 1993; Moyle 2002).

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References

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