Micropterus dolomieu

Invasion History

First Non-native North American Tidal Record: 1855
First Non-native West Coast Tidal Record: 1874
First Non-native East/Gulf Coast Tidal Record: 1855

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General Invasion History:

Smallmouth Bass (Micropterus dolomieu) is native to the Great Lakes, Hudson Bay, and upper Mississippi basins, from south Quebec to North Dakota and south to north Alabama and eastern Oklahoma (Page and Burr 1991). It was widely introduced by United States Fish Commission (USFC) and state fish commissions. In 1893 the United States Fish Commission shipped mixed batches of Smallmouth Bass and Largemouth Bass to 29 states as 'Black Bass' (Worth 1895). Smallmouth Bass was introduced to California in 1874 (Carlander 1977). Shipments and stocking by United States Fish Commission continued into the 1920s. After 1905, Smallmouth Bass and Largemouth Bass were listed separately in United States Fish Commission records. Stocking was continued by many state agencies to the present day. Micropterus dolomieu now have been introduced to river systems in 43 states, including Hawaii (Fuller et al. 1999). They have been introduced to the Columbia River and San Francisco estuaries, Atlantic estuaries from Virginia to New Brunswick, and many interior basins outside their native range (Fuller et al. 1999; USGS Nonindigenous Aquatic Species Program 2018). In addition, they have been introduced to countries in Europe, Asia, Africa, and South America (Food and Agriculture Organization 2018; Lever 1996). The range of the Smallmouth Bass is limited by a preference for cooler flowing or well-oxygenated waters (Page and Burr 1991).

North American Invasion History:

Invasion History on the West Coast:

Smallmouth Bass were first introduced to California and the San Francisco Bay watershed by Livingstone Stone, California Fisheries Commissioner, in 1874, with 73 adult fish from Lake Champlain, Vermont released into Napa Creek, and 12 small fish from Michigan stocked in Alameda Creek. The Napa Creek population was quickly fished out, but the Alameda Creek population became established. Additional stocking occurred in lakes and reservoirs around the Bay, and in river systems throughout California (Smith 1895; Dill and Cordone 1997). In the San Francisco estuary, Smallmouth Bass are largely confined to dead-end sloughs and the freshwater edges of the Delta (Wang 1986). Leidy (2007) reported records from San Lorenzo, Alameda, and Coyote Creeks, and the Guadalupe and Napa Rivers. In surveys of the freshwater Delta, Smallmouth Bass were a small fraction (0.2-0.3 %) of the total catch (Feyrer and Healy 2003; Brown and Michniuk 2007).

Smallmouth Bass were first introduced to the Columbia River system by an Oregon game warden who planted 425 fish, from Wisconsin, in Oswego Lake, Portland, adjacent to the Willamette River in 1924. In 1925, another stocking of Smallmouth Bass was made in the upper Willamette. By 1946, Smallmouth Bass were established in the backwaters of the lower Columbia River (Chapman 1942), the Yakima River, Washington, and the upper and lower Willamette (Lampman 1946). Smallmouth Bass were common in the lower Willamette River in 1987–1990 (Farr and Ward 1994). Two specimens were caught in a survey of Columbia Slough, Portland (2008–2009, Van Dyke et al. 2008).

Smallmouth Bass have been introduced to lakes in the interior Fraser River Basin, British Columbia, and are regarded as a threat to native fish populations, especially salmonids (McPhail 2008; Department of Fisheries and Oceans 2011). Modeling studies indicate a high potential for establishment in the lower Fraser River Basin, the Thompson River Basin, and streams of southern Vancouver Island (Sharma et al. 2009).

Invasion History on the East Coast:

Smallmouth Bass were introduced separately to many Atlantic river basins from the Savannah River (Georgia-South Carolina) to New Brunswick. South of the Potomac River, they are largely confined to Piedmont and Mountain rivers and reservoirs (Jenkins and Burkhead 1993; Rodhe et al. 1994). Further north, they are generally found in the nontidal sections of rivers, and close to the head of tide in estuaries, favoring cooler water, rock and gravel substrate, and stronger currents (Hildebrand and Schroeder 1928; Pavol and Davis 1982). The Smallmouth Bass was an early introduction to East Coast river systems. It may have been introduced to the Hudson River through the Erie Canal as early as the 1830s, though the Smallmouth and Largemouth Basses were not clearly distinguished in records until 1903 (Mills et al. 1997; Daniels et al. 2005). Other early watershed records were the Potomac (1854), the Susquehanna (1869), the Delaware (1873), the Connecticut (1855), the Kennebec & Penobscot (after 1869).

The Smallmouth Bass was introduced to the Potomac River in 1854 by railroad workers who put 20 adult fish from the Youghiogheny River (Ohio drainage) into a locomotive water-tank and released in the Chesapeake & Ohio Canal, on the Potomac River, near Cumberland (Smith 1907). Additional stocking in Potomac drainage occurred from the 1860s onward. By 1876, the first Maryland fish survey reported that this fish 'abounds' in the Potomac in Montgomery, Frederick, and Washington Counties (Uhler and Lugger 1876). 'Inside of ten years, the fish literally swarmed in all the tributaries from Mount Vernon to the Headwaters. At the present time the species offers much sport from Washington to Harpers Ferry and beyond, but is not common below the capital' (Smith 1907). Smallmouth Bass were stocked in the Susquehanna sometime around 1869 (Pennsylvania Department of Fisheries 1904; cited by Bielo 1963), and were abundant in the tidal river near Havre de Grace by 1883 (Bean 1893). A resident population below Conowingo Dam moves from non-tidal waters in winter and spring to tidal fresh waters as oxygen concentrations in the nontidal river drop in summer (Pavol and Davis 1982). Smallmouth Bass were collected in the Bohemia River (Fowler 1912; Radcliffe and Welsh 1917) and at Love Point (Hildebrand and Schroeder 1928) in upper Chesapeake Bay. One specimen was caught in the Rhode River at SERC in 1983 (Rob Aguilar, personal communication), but this species is rarely collected in brackish bay waters (Murdy et al. 1997).

Smallmouth Bass were present in the Delaware estuary at Trenton, New Jersey, by 1873 (Abbot 1877), probably introduced by private stockings, or perhaps through canals from the Hudson River. There were also numerous stockings, including one in the Delaware River, PA (405 fish; Bean 1893), and in Brandywine Creek, Delaware, in 1888 and 1903 (Raasch and Altemus 1991). These bass are now resident in the Delaware estuary (Horwitz 1986; Raasch and Altemus 1991). Weisberg et al. (1996) collected them only in the upper estuary, from Philadelphia to Trenton.

De Kay (1842) described the 'Black Huron' ('Huro nigricans'), a bass from the Great Lakes, but did not report it from the Hudson River. Both Largemouth and Smallmouth were present in the tidal Hudson River by 1903, but probably entered the river after the completion of the Erie Canal in 1827. It is currently present through the Mohawk and Hudson Rivers (Mills et al. 1997; Daniels et al. 2005).

The Smallmouth Bass was introduced to Connecticut in the 1850s (Whitworth 1996), and is well-established in the tidal Connecticut River from Hartford to East Haddam (Whitworth 1968; Marcy 1976; Connecticut Department of Environmental Protection 1998); and in the Thames River estuary (1973, Jacobson 1980).

Smallmouth Bass were introduced to Maine in 1868–1881 in lakes in many river drainages across Maine, including the Saco, Androscoggin, Kennebec, Penobscot and Saint Croix (Everhart 1966; Warner 2005). These bass have been found in Merrymeeting Bay, the Kennebec-Androscoggin estuary (Kennebec Fisheries Council 1999) and the Penobscot estuary (O'Malley et al. 2010), and likely occur in tidal fresh waters of other Maine rivers. Smallmouth Bass from Maine were officially stocked into New Brunswick and Nova Scotia rivers flowing into the Bay of Fundy from 1905 to 1953, and further spread by informal stocking. Since 1998, Smallmouth have been stocked into rivers flowing into the Gulf of St. Lawrence in New Brunswick and Nova Scotia. In 2008, it was discovered at the head Miramichi River drainage, New Brunswick, far inland, but of great concern because of its status as a major Atlantic Salmon river (LeBlanc et al. 2021).

Invasion History in Hawaii:

An early attempt to introduce Smallmouth Bass to the island of Hawaii in 1897 was unsuccessful. In 1953–58, Smallmouth Bass were introduced to streams and reservoirs on Oahu, Hawaii, and Kauai (Brock 1960; Lever 1996; USGS Nonindigenous Aquatic Species Program 2018).

Invasion History Elsewhere in the World:

Smallmouth Bass have been widely introduced in the interior of North America to 29 US states, 7 Canadian provinces, and northern Mexico (Lever 1996; Brown et al. 2009). In eastern Canada, its range is shifting northward, due to a combination of natural dispersal, climate change, and human introductions (Loppnow et al. 2013).

Smallmouth Bass have been introduced to 20 countries, but most of these introductions have been unsuccessful (Froese and Pauly 2018). In 1938, this fish was introduced to South Africa, and is established in Cape and Natal provinces, mostly in upland streams and reservoirs (Lever 1996). In the 1990s, Smallmouth Bass were introduced to Lake Aoki, central Honshu, Japan (Iguchi and Yodo 2004). Its range is limited to central Honshu, but modeling suggest that it could occupy regions on all of the islands of Japan (Iguchi et al. 2004).

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Description

The Smallmouth Bass (Micropterus dolomieu) 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 that extends 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 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).

The Smallmouth Bass is somewhat streamlined, with the dorsal profile of the head slightly convex. The mouth is smaller than that of the Largemouth Bass, with the upper jaw not extending past the rear half of the eye. There are 69–73 lateral line scales, 9–11 dorsal spines, 12–15 dorsal rays, 3 anal spines, and 9–12 anal rays The fish can grow to 690 mm, but a more usual large size is 400 mm. The body is olive-brown to green-brown above with dark mottling on the back and sides, and yellowish white below. The mottling on the sides is often condensed into dark bars (Page and Burr 1991; Moyle 2002).

In the 19th century, 'Black Basses' (Smallmouth and Largemouth) were frequently confused, especially when transported for stocking (Smith 1895), or in distributional records. The many Southeastern bass species (Spotted Bass—M. punctulatus; Redeye Bass—M. coosae; Shoal Bass—M. cataractae; Suwanee Bass—M. notius; Guadalupe Bass—M. treculi) were historically confused with Smallmouth Bass (Jenkins and Burkhead 1993).

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Taxonomy

Ecology

General:

The Smallmouth Bass (Micropterus dolomieu) is a freshwater predatory fish. Adults can mature at 2 years, or as late as 9 years, but more usually at age 3–4. Virginia and California populations at age 3 to 4 range from 190 to 410 mm at these ages (Jenkins and Burkhead 1994; Moyle 2002). Spawning takes place at 16–27 C, in freshwater, often moving upstream in tributaries. Adult male fish move into shallow water, ~1 m deep, near shore, and excavate a nest in sand, gravel, or rock (Hardy 1978; Wang 1986; Jenkins and Burkhead 1993; Moyle 2002). Males guard a nesting site against other males, and court females. Females may spawn with more than one male, and males may spawn with more than female. Females can carry ~2,000–21,000 eggs. Males vigorously guard the eggs through hatching and until the larvae reach 20–30 mm. Eggs take 2.5–9 days to develop at 15–26 C (Hardy 1978; Jenkins and Burkhead 1994; Moyle 2002).

Smallmouth Bass inhabit clear gravel-bottom runs and flowing pools of small to large rivers, and the rocky shoals of lakes (Hardy 1978; Page and Burr 1991; Wang 1986). In the Chesapeake Bay region, it is common in the Piedmont and Fall Line, the bottoms are rocky, and currents are strong, but this fish is rare in the Coastal Plain region, where currents are slower, temperatures are higher, and oxygen is lower (Jenkins and Burkhead 1993; Murdy et al. 1997). Preferred temperatures are 20–28 C, but Smallmouth Bass have been collected at 4 °C and have an experimental upper lethal temperature of 35 °C (Hardy 1978). They are rare in brackish water, but have been collected at 7.4 PSU (Hildebrand and Schroeder 1928). Smallmouth Bass tolerates dissolved oxygen of 0.9-1.0 ppm at 21 °C, but is usually associated with well-oxygenated waters (Carlander 1977). Juveniles feed on microcrustaceans and insects, and switch to fish and crayfish as they grow. Other prey include amphibians, insects, and other Smallmouth Bass (Jenkins and Burkhead 1993; Moyle 2002). The Largemouth (M. salmoides) and Spotted Bass (M. punctulatus) are potential competitors. Humans are the primary predators of adult fish as the Smallmouth is an esteemed gamefish.

Food:

insects; amphipods. crayfish; fishes

Consumers:

fishes, mammals, birds, humans

Competitors:

Micropterus spp.

Trophic Status:

Carnivore

Carn

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Habitats

General Habitat	Nontidal Freshwater	None
General Habitat	Fresh (nontidal) Marsh	None
General Habitat	Tidal Fresh Marsh	None
General Habitat	Coarse Woody Debris	None
General Habitat	Rocky	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)	4.4	Experimental (Hardy 1978)
Maximum Temperature (ºC)	35	Experimental (Hardy 1978; Brown et al. 2009)
Minimum Salinity (‰)	0	This is a freshwater fish.
Maximum Salinity (‰)	7.4	Field (Hardy 1978)
Minimum pH	4.1	Carlander 1977
Maximum pH	9.3	Carlander 1977
Minimum Reproductive Temperature	18.3	Hardy 1978
Maximum Reproductive Temperature	26.7	Hardy 1978
Minimum Reproductive Salinity	0	None
Minimum Length (mm)	195	Minimum adult size, Hardy 1978
Maximum Length (mm)	686	Hardy 1978

General Impacts

The Smallmouth Bass (Micropterus dolomieu) is an apex predator in river systems and a popular gamefish, widely introduced for food and sport. Where it has been introduced it is popular for its fighting qualities, but also raises concern as a predator on native fishes, especially anadromous salmonids and American Shad (Alosa sapidissima) in North America and native fishes in South Africa (Johnson and Dropkin 1992; Loppnow et al. 2011; LeBlanc et al. 2021).

Economic Impacts-

Fisheries- Smallmouth Bass were initially stocked and promoted as a food-fish, it is now mostly prized as a gamefish because of its size and fighting qualities (Brown et al. 2009). Its impact in fishing within the tidal limits of estuaries is small because of its preference for cool, clear, flowing waters, but it is important in the upland portions of watersheds, and can influence estuarine fisheries indirectly, through competition and predation with anadromous fishes, such as American Shad (Alosa sapidissima, Atlantic Salmon (Salmo salar, Chinook Salmon (Oncorynchus tshawytscha, or Steelhead (O. mykiss). Because of widespread disturbance to rivers through dams, pollution, and overfishing, the historical effects of Smallmouth Bass introductions are difficult to determine. However, predation by Smallmouth Bass and other introduced species has complicated restoration programs (Johnson and Dropkin 1992; U.S. Fish and Wildlife Service 1999; LeBlanc et al. 2021).

Smallmouth Bass were a major sport fisheries introduction to South Africa, intended to fill the gap between the upland trout populations, and the sluggish lowland Largemouth Bass waters. They have provided a sport fishery, but reduced or eliminated some native fish populations (Lever. 1996).

Ecological Impacts-

Predation- Smallmouth Bass (Micropterus dolomieu) has been introduced to many watersheds in North America, and some in South Africa and Japan, where there were few or no native, relatively large, spiny-rayed fishes. Soon after its introduction in the Potomac River, Smallmouth Bass were blamed by fishermen for the decrease of American Shad and "chubs, minnows, and suckers" in the upper Potomac (Ferguson 1877), although overfishing, dams, and pollution were also affecting the fisheries. In lakes and rivers of the Pacific Northwest, Smallmouth Bass predation on native trout, salmon, and minnows is significant. Bass predation on anadromous Pacific salmon (Oncorhynchus spp.) is especially problematic, because the salmon are protected by the Endangered Species Act (Carey et al. 2011). Similarly, Smallmouth Bass in the Atlantic are considered to be a moderate threat to Atlantic Salmon populations (Salmo salar) in the Maritime Provinces and Maine (U.S. Fish and Wildlife Service 1999; https://waves-vagues.dfo-mpo.gc.ca/Library/40989276.pdf). In South Africa, predation by Smallmouth Bass led to the decline and local extinction of some local cyprinid species (Barbus spp.) (Lever 1996).

Competition-Juvenile Smallmouth Bass which feed on zooplankton, insects, and small crustaceans, are competitors with juvenile salmonids and minnows for food, while adults can compete with native predators, such as the Pikeminnows Ptychocheilus. spp. of Pacific Slope rivers (Harvey and Kareiva 2005).

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Regional Impacts

M130	Chesapeake Bay		Ecological Impact	Predation
Impacts of Smallmouth Bass (Micropterus dolomieu) in the tidal waters of the Bay are probably limited by the low abundance of this primarily freshwater river species, but it is an important predator above the Fall-Line (Jenkins and Burkhead 1993) and in the Susquehanna River below Conowingo Dam (Pavol and Davis 1982. Predation - Smallmouth Bass is one of the major piscivorous species in nontidal Chesapeake tributaries and in the tidal Susquehanna. Soon after its introduction, it was blamed by fishermen for the decrease of shad and "chubs, minnows, and suckers" in the upper Potomac (Ferguson 1876). Ferguson considered that while "Black Bass" were responsible for significant predation, dams, and other obstructions of fish movement were the major factor in decline of these fishes and of bass populations themselves in the upper river. In the tidal Susquehanna, major native prey species included Tesselated Darter (Etheostoma olmstedi), White Perch (Morone americana), and Gizzard Shad (Dorosoma cepedianum) (Pavol and Davis 1982). Jenkins and Burkhead (1993) and others have suggested the introduction of large predatory fishes (primarily Smallmouth Bass, Largemouth Bass (M. salmoides), and (Channel Catfish Ictalurus punctatus)) may have been responsible for the extinction of two small benthic fishes, Percina caprodes (Logperch) in the Potomac, and Percopsis oniscomaycus (Troutperch), in the entire Chesapeake drainage. Predation on juveniles of many other species is likely. Smallmouth Bass fed heavily on larval shad (Alosa sapidissima) newly released in the Susquehanna River in Pennsylvania, within 30–60 minutes after stocking (Johnson and Dropkin 1992). The extent of predation on natural larval populations of shad and other anadromous fishes in the Chesapeake Basin is not known. Smallmouth Bass are also important as a predator of crayfishes (Rabeni et al. 1992) and probably other large benthic invertebrates in streams. For Smallmouth Bass in the tidal Susquehanna River, insects and crustaceans together comprised 29% of food items by number, but only 1.6% of volume, suggesting that crayfishes were not important as prey in those waters (Pavol and Davis 1982).
M130	Chesapeake Bay		Economic Impact	Fisheries
Fisheries - Smallmouth Bass (Micropterus dolomieu) is a major sportfish in nontidal rivers entering Chesapeake Bay and a minor sportfish in the upper Bay (e.g. lower Susquehanna; Susquehanna flats, Northeast River MD, (Elser 1960; Mansueti 1964; Plosila 1961). It is also a predator on larval shad in nontidal waters (Johnson and Dropkin 1992) and probably on other juvenile sport and game fish.
N090	Kennebec/Androscoggin River		Ecological Impact	Predation
Predation - Smallmouth Bass (Micropterus dolomieu) is one of the major piscivorous species in nontidal tributaries and in upper reaches of major East Coast estuaries, including the Connecticut River. In New England rivers, it is considered a major predator of Atlantic Salmon juveniles (Salmo salar) (US Fish and Wildlife Service 1999).
M040	Long Island Sound		Ecological Impact	Predation
Predation - Micropterus dolomieu (Smallmouth Bass) is one of the major piscivorous species in nontidal tributaries and in upper reaches of major East Coast estuaries, including the Connecticut River. In New England rivers, it is considered a major predator of Atlantic Salmon juveniles (Salmo salar) (US Fish and Wildlife Service 1999).
N050	Penobscot Bay		Ecological Impact	Predation
Predation- Smallmouth Bass (Micropterus dolomieu) is one of the major piscivorous species in nontidal tributaries and in upper reaches of major East Coast estuaries In New England rivers, it is considered a major predator of Atlantic Salmon juveniles (Salmo salar) (US Fish and Wildlife Service 1999).
M060	Hudson River/Raritan Bay		Ecological Impact	Predation
Impacts of Smallmouth Bass (Micropterus dolomieu) in East Coast estuaries are probably limited by the low abundance of this primarily freshwater river species, especially in the Mid-Atlantic states, but it is an important predator in upland rivers (Jenkins and Burkhead 1993) and can affect anadromous fish populations. Smallmouth Bass is considered a major predator in the Hudson River (Mills et al. 1997).
N090	Kennebec/Androscoggin River		Economic Impact	Fisheries
Smallmouth Bass (Micropterus salmoides ) is a highly prized sport fish in Gulf of Maine rivers, including the Merrimack, Kennebec, Penobscot, and others (Everhart 1966; Hartel et al. 1996). Its negative fisheries impacts on Atlantic drainage fish communities and fisheries have not been well studied. Effects on freshwater fishes are probably small, because most of the native freshwater species coincide with Micropterus dolomieu in other parts of their range. However, interactions with anadromous fishes such as American Shad (Alosa sapidissima, Alewives (A. pseudoharengus) and Atlantic Salmon (em>Salmo salar). Smallmouth Bass is considered to be a major predator on Atlantic Salmon (US Fish and Wildlife Service 1999).
N050	Penobscot Bay		Economic Impact	Fisheries
Smallmouth Bass (Micropterus dolomieu) is a highly prized sport fish in Gulf of Maine rivers, including the Merrimack, Kennebec, Penobscot, and others (Everhart 1966; Hartel et al. 1996). Its negative fisheries impacts on Atlantic drainage fish communities and fisheries have not been well studied. Smallmouth Bass is considered to be a major predator on Atlantic Salmon (Salmo slar (US Fish and Wildlife Service 1999).
P090	San Francisco Bay		Economic Impact	Fisheries
Smallmouth Bass have minor, localized importance as a sport fish in California (Dill and Cordone 2007)
P260	Columbia River		Economic Impact	Fisheries
Smallmouth Bass are a highly valued sportfish in Pacific Northwest fishes and lakes, with an estimated 140,000 bass anglers in Washington, Oregon, and Idaho, spending ~$66 million (2006 estimates). Smallmouth Bass have proliferated in the Columbia River system reservoirs. The population has been favored by rising temperatures. Smallmouth Bass overlap with migrating juvenile Chinook Salmon (Oncorhynchus tshawytscha) and Steelhead (O. mykiss) in part of the year, and at times salmon form a significant part of the basses' diet. Young Smallmouth Bass also compete with juvenile salmon for zooplankton, insects, and crayfish. Salmon and Steelhead fisheries are of equal or greater economic value to the bass fishery, so the challenge for fisheries management is to find strategies that preserve native fish populations and support sport fisheries Chinook Salmon populations are protected by the Endangered Species Act (Carey et al. 2011).
P260	Columbia River		Ecological Impact	Predation
Smallmouth Bass have become an important predator in Columbia River system reservoirs. The population has been favored by rising temperatures. Smallmouth Bass overlap with migrating juvenile Chinook Salmon (Oncorhynchus tshawytscha) and Steelhead (O. mykiss) in part of the year, and at times salmon and steelhead form a significant part of the basses' diet (Harvey and Kareiva 2005; Sanderson et al. 2009; Carey et al. 2011). The Smallmouth Bass's impact on salmonids is large because its large gape permits it to start predation at a smaller size, 150-200 mm and earlier age than the native Northern Pikeminnow (Ptychocheilus oregonensis), increasing the predation risk (Fritts and Pearson 2006). Smallmouth Bass in the Columbia River basin consume and estimated 18,000 to 2,000,000 juvenile salmonids per year at various locations (Sanderson 2009).
P260	Columbia River		Ecological Impact	Competition
Young Smallmouth Bass also compete with juvenile salmon for zooplankton, insects, and crayfish. Adult Smallmouth Bass compete with native predators, mostly Northern Pikeminnow (Ptychocheilus oregonensis) (Harvey and Kareiva 2005; Carey et al. 2005).
N050	Penobscot Bay		Ecological Impact	Competition
In an experimental stream, juvenile Smallmouth Bass and Atlantic Salmon showed little habitat overlap, with Salmon preferring riffles, and Bass preferring pools (Wathen et al. 2012). However, with a wider range of age-classes and habits, competition and predation interactions could be more apparent.
P090	San Francisco Bay		Ecological Impact	Predation
In California, predation by Smallmouth Bassu was correlated with a decline in the native cyprinid Mylodon conocephalus (Hardhead), and may have had adverse effects on other native species (Dill and Cordone 1997).
CA	California		Ecological Impact	Predation
In California, predation by Smallmouth Bassu was correlated with a decline in the native cyprinid Mylodon conocephalus (Hardhead), and may have had adverse effects on other native species (Dill and Cordone 1997).
CA	California		Economic Impact	Fisheries
Smallmouth Bass have minor, localized importance as a sport fish in California (Dill and Cordone 2007)
ME	Maine		Ecological Impact	Competition
In an experimental stream, juvenile Smallmouth Bass and Atlantic Salmon showed little habitat overlap, with Salmon preferring riffles, and Bass preferring pools (Wathen et al. 2012). However, with a wider range of age-classes and habits, competition and predation interactions could be more apparent.
ME	Maine		Ecological Impact	Predation
Predation- Smallmouth Bass (Micropterus dolomieu) is one of the major piscivorous species in nontidal tributaries and in upper reaches of major East Coast estuaries In New England rivers, it is considered a major predator of Atlantic Salmon juveniles (Salmo salar) (US Fish and Wildlife Service 1999)., Predation - Smallmouth Bass (Micropterus dolomieu) is one of the major piscivorous species in nontidal tributaries and in upper reaches of major East Coast estuaries, including the Connecticut River. In New England rivers, it is considered a major predator of Atlantic Salmon juveniles (Salmo salar) (US Fish and Wildlife Service 1999).
ME	Maine		Economic Impact	Fisheries
Smallmouth Bass (Micropterus dolomieu) is a highly prized sport fish in Gulf of Maine rivers, including the Merrimack, Kennebec, Penobscot, and others (Everhart 1966; Hartel et al. 1996). Its negative fisheries impacts on Atlantic drainage fish communities and fisheries have not been well studied. Smallmouth Bass is considered to be a major predator on Atlantic Salmon (Salmo slar (US Fish and Wildlife Service 1999)., Smallmouth Bass (Micropterus salmoides ) is a highly prized sport fish in Gulf of Maine rivers, including the Merrimack, Kennebec, Penobscot, and others (Everhart 1966; Hartel et al. 1996). Its negative fisheries impacts on Atlantic drainage fish communities and fisheries have not been well studied. Effects on freshwater fishes are probably small, because most of the native freshwater species coincide with Micropterus dolomieu in other parts of their range. However, interactions with anadromous fishes such as American Shad (Alosa sapidissima, Alewives (A. pseudoharengus) and Atlantic Salmon (em>Salmo salar). Smallmouth Bass is considered to be a major predator on Atlantic Salmon (US Fish and Wildlife Service 1999).

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