Invasion History

First Non-native North American Tidal Record: 1999
First Non-native West Coast Tidal Record: 1999
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

Redeye Bass (Micropterus coosae) are native to a limited range in the Coosa River basin, in the Appalachians and Piedmont in Alabama, Georgia, and Tennessee (Baker et al. 2013). They inhabit rocky runs and pools of streams and small rivers (Page and Burr 1991). They have been introduced to the San Francisco Bay watershed, to scattered drainages in California, to scattered Southeastern drainages outside the native range, and Puerto Rico (USGS Nonindigenous Aquatic Species Program 2022).

North American Invasion History:

Invasion History on the West Coast:

Redeye Bass, from the Sheeds Creek, tributary to the Conasauga River (a Coosa River tributary), were introduced to Alder Creek, a Sacramento River tributary in 1963, as well as other California streams (Dill and Cordone 1997; USGS Nonindigenous Aquatic Species Program 2018). Redeye Bass were chosen for stocking in small, warm, swift flowing rivers, because of their high temperature tolerance and habitat preferences. Introductions were made in many Sacramento-San Joaquin tributaries, in the Santa Margarita River, San Diego County, and in the Sisquoc River, Santa Barbara County (Dill and Cordone 1997; USGS Nonindigenous Aquatic Species Program 2018). By 1999, this species was found in the Delta. In the Cosumnes River, it was found from tributaries at 561m elevation down to the tidal floodplain, and was the most abundant of the four Black Bass species in the river system (Moyle et al. 2002). In 2010, in the North Fork Mokelumne River in the Delta, M. coosae was the second most abundant of the four species of 'Black Bass' (Carvallo et al. 2014). At present, Redeye Bass appear to be confined to the inland freshwater edges of the Delta.

Invasion History Elsewhere in the World:

Redeye Bass were brought to a hatchery in Puerto Rico in 1958–1959, and released in rivers and reservoirs, starting in 1964. Populations are established in several rivers and reservoirs in Puerto Rico (Lever 1996; USGS Nonindigenous Aquatic Species Program 2018).


The Redeye Bass (Micropterus coosae) is a large predatory freshwater fish. Fishes of the family Centrarchidae (Sunfishes and Black Basses) have a 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. Black Basses (Micropterus spp.) are large (over 360 mm), moderately laterally compressed, with an elongated body and a large mouth, extending under or past the eye. The base of the anal fin is less than half the length of the dorsal fin. The tail fin is shallowly forked. There is a black spot at the rear angle of the gill cover but no gill flap. There are dark brown lines radiating from the snout and back of the eye to the rear edge of the gill-cover (Page and Burr 1991).

Moyle (2002) described the Redeye Bass as 'brightly colored'. Specific characters of the Redeye Bass include a large mouth, with the upper jaw extending under the rear half of the eye, 64–73 lateral line scales, 9–11 dorsal spines, 12 dorsal rays, 3 anal spines, and 9–11 anal rays (Page and Burr 1991; Moyle 2002). The fish can grow to 390–470 mm. The body is bronze-olive above, with dark olive mottling, and yellowish white to bluish-white below. There are usually dark bars on the upper side, and lateral rows of dark spots. The bars become diamond-shaped sport towards the base of the caudal peduncle. The fins and eye are brick-red, while the upper and lower margins of the tail fin are white (Page and Burr 1991; Moyle 2002). It is frequently confused with the Smallmouth Bass (M. dolomieu), but is smaller, and more brightly colored, reaching 410 mm in reservoirs, but more usually 200 to 350 mm (Moyle 2002)

The former 'Redeye Bass' (Micropterus 'coosae') has been divided into a complex of 6 species: M. coosae, M. cahabae, M. tallapoosae, M. warriorensis, and M. chattahoochae, named according to their different river systems (Baker et al. 2013; Kim et al. 2022). A sixth species, undescribed, M sp. cf. coosae (Bartram's Bass) is native to the upper Savannah River (Bangs et al. 2018). The fish introduced to California came from the Sheeds Creek, a tributary to the Conasauga River which is a tributary of the Coosa River (Dill and Cordone 1997), and so are likely to be M. coosae (Moyle 2002).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Chordata
Subphylum:   Vertebrata
Superclass:   Osteichthyes
Class:   Actinopterygii
Subclass:   Neopterygii
Infraclass:   Teleostei
Superorder:   Acanthopterygii
Order:   Perciformes
Suborder:   Percoidei
Family:   Centrarchidae
Genus:   Micropterus
Species:   coosae


Potentially Misidentified Species

Micropterus dolomieu
Smallmouth Bass (Micropterus dolomieu) has clear fins, 8-16 dark bars on the side, and lacks rows of spots. It is native to the Great Lakes, upper Mississippi Basin, and is introduced to San Francisco and Columbia River estuaries, and Northeastern estuaries from Maine to Virginia. Smallmouth Bass are found in cool lakes and flowing waters (Page and Burr 1991).

Micropterus henshalli

Alabama Bass (Micropterus henshalli) was formerly regarded as a subpecies of M. punctulatus. It is native to central Alabama. It was stocked in Millerton Lake in the San Joaquin River in 1974. Both Spotted and Alabama Bass are established in the San Francisco etuary watershed (Dill and Cordone 1997).

Micropterus punctulatus
Spotted Bass (Micropterus punctulatus) have clear fins, and a row of large dark spots along the lateral line, with rows of dots below. Spotted Bass are native to the upper Mississippi-Gulf basins, and are associated with clear, flowing rivers (Page and Burr 1991). Spotted Bass have been introduced to the San Francisco estuary watershed, Virginia tributaries of Chesapeake Bay, and South Africa (Jenkins and Burkehad 1993; Lever 1996; Dill and Cordone 1997).

Micropterus salmoides
Largemouth Bass (Micropterus salmoides) has a large mouth, with the upper jaw extending past the eye. The front and rear dorsal are nearly separate. There is a broad, black band extending from the eye to the tail, sometimes broken up into blotches. Largemouth Bass are characteristic of lakes and large rivers, with clear water and dense vegetation. Largemouth Bass are native to the Great-Lakes-Mississippi Basin, and the Atlantic Slope from North Carlina to Florida. It is introduced to the Columbia River and San Francisco estuaries, and from Chesapeake Bay to Maine (Page and Burr 1991).



Redeye Bass (Micropterus coosae) are a large, predatory, freshwater fish. Information on their life history is limited, but is probably similar to that of the Spotted and Smallmouth Bass. They mature at 120–130 mm, at about 2–4 years of age. Females contain about 2000–2300 eggs. Adults move into pools of headwater streams at a temperature of 12–21 C. Males construct a nest by excavating a shallow pit in the substrate. After the female deposits the eggs, the male guard the nest until the eggs hatch (Rohde et al. 1994; Moyle 2002; California Fish Website 2014).

Redeye Bass have a limited native range in the Appalachian mountains and foothill streams in Georgia, Tennessee, and Alabama. Exact temperature tolerances are not published, but these fish tolerate cool winters and warm summers. They were selected for stocking in smaller California foothill streams because they tolerate higher temperatures than trout, and due to their smaller size are more capable of colonizing small streams (Dill and Cordone 1997). They have not been reported from brackish water. Habitats include 'rocky runs and pools of creeks and small to medium rivers' (Page and Burr 1998). In the Delta, they are known from locations where upland rivers such as the Mokelumne and Cosumnes flow into the Delta (Moyle et al. 2002; Cavallo et al. 2013). Redeye Bass feed like trout, relying heavily on terrestrial insects, but also aquatic insects, crayfish, and small fishes (Moyle 2010). They are competitors with Smallmouth Bass (M. dolomieu), Spotted Bass (M. punctulatus), and to a lesser extent Largemouth Bass (M. salmoides). Predators include other large fishes, especially other Black Basses, and humans. 


insects, crayfish, fishes


fishes, birds, mammals, humans


Micropterus spp.

Trophic Status:




General HabitatNontidal FreshwaterNone
General HabitatGrass BedNone
General HabitatCoarse Woody DebrisNone
General HabitatTidal Fresh MarshNone
General HabitatUnstructured BottomNone
General HabitatRockyNone
Salinity RangeLimnetic0-0.5 PSU
Tidal RangeSubtidalNone
Vertical HabitatNektonicNone

Life History

Tolerances and Life History Parameters

Minimum Salinity (‰)0This is a freshwater fish.
Minimum Reproductive Temperature17Moyle 2002
Minimum Length (mm)120Length at maturity, Moyle 2002
Maximum Length (mm)470Page and Burr 1991
Broad Temperature RangeNoneWarm-Temperate
Broad Salinity RangeNoneLimnetic-Oligohaline

General Impacts

Redeye Bass (Micropterus coosae) is established and apparently rare to common in some eastern foothill Delta tributaries. Moyle (2002) considered the introduction largely unsuccessful because of the small size of the fish and limited fishing interest. The high abundance in the Consumne and Stanisaus Rivers represents a threat to native fishes (Moyle 2002). Cavallo et al. (2014) found that removal of predators dominated by Redeye and Spotted Bass (M. punctulatus), enhanced the survival of tagged Chinook Salmon (Oncorhynchus tshawytscha) smolts. Web postings about this fish in California are mostly of the 'What is this strange-looking bass?' variety.

Regional Impacts

P090San Francisco BayEcological ImpactPredation
Removal of predators, dominated by Redeye Bass (Micropterus coosae) and Spotted Bass (M. punctulatus), by electrofishing, enhances the survival of tagged Chinook Salmon in migration through the North Fork of the North Fork Mokelumne River (Cavallo et al. 2013).
CACaliforniaEcological ImpactPredation
Removal of predators, dominated by Redeye Bass (Micropterus coosae) and Spotted Bass (M. punctulatus), by electrofishing, enhances the survival of tagged Chinook Salmon in migration through the North Fork of the North Fork Mokelumne River (Cavallo et al. 2013).

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
P090 San Francisco Bay 1999 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Kim, Daemin; Taylor, Andrew T.; Near, Thomas J. (2022) Phylogenomics and species delimitation of the economically important Black Basses (Micropterus), Scientific Reports 12(9112): Published online

Baker, Winston; Blanton, Rebecca E,; Johnstov, Carol E. (2013) Diversity within the Redeye Bass, Micropterus coosae (Perciformes: Centrarchidae) species group, with descriptions of four new species, Zootaxa 3635(4): 379-401

Bangs, Max R.; Oswald, Kenneth J.; Greig, Thomas W.; Leitner, Jean K.; Rankin, Daniel M.; Quattro, Joseph M. (2018) Introgressive hybridization and species turnover in reservoirs: a case study involving endemic and invasive basses (Centrarchidae: Micropterus) in southeastern North America, Conservation Genetics 19: 57-69
DOI 10.1007/s10592-017-1018-7

Cavallo, Bradley; Merz, Joseph; Setka, Jose (2013) Effects of predator and flow manipulation on Chinook salmon (Oncorhynchus tshawytscha) survival in an imperiled estuary, Environmental Biology of Fishes 393: 393-403

Jenkins, Robert E.; Burkhead, Noel M. (1993) Freshwater Fishes of Virginia, American Fisheries Society, Bethesda, MD. Pp. <missing location>

Kim, Daemin; Taylor, Andrew T.; Near, Thomas J. (2022) Phylogenomics and species delimitation of the economically important Black Basses (Micropterus), Scientific Reports 12(9113): Published online

Lever, Christopher (1996) Naturalized fishes of the world, Academic Press, London, England. Pp. <missing location>

Light, Theo; Grosholtz, Ted; Moyle, Peter (2005) Delta ecological survey (phase1): Nonindigenous aquatic species in the Sacramento-San Joaquin Delta, a literature review, In: None(Eds.) None. , Stockton, CA. Pp. <missing location>

Moyle, Peter B. (2002) Inland Fishes of California, revised and expanded, University of California Press, Berkeley CA. Pp. <missing location>

Page, Lawrence M.; Burr, Brooks M. (1991) Freshwater Fishes: North America North of Mexico, Houghton-Mifflin, Boston. Pp. <missing location>

Rohde, Fred C.; Arndt, Rudolf G.; Lindquist, David G.; Parnell, James F. (1994) Freshwater fishes of the Carolinas, Virginia, and Delaware, Universilty of North Carolina Press, Chapel Hill NC. Pp. <missing location>

Salmon, Terry and 21 authors 2014-2022 California Fish Website.

USGS Nonindigenous Aquatic Species Program 2003-2024 Nonindigenous Aquatic Species Database.