Lepomis cyanellus (green sunfish)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Biology and Ecology
- Natural Food Sources
- Water Tolerances
- Natural enemies
- Means of Movement and Dispersal
- Pathway Causes
- Pathway Vectors
- Impact Summary
- Economic Impact
- Environmental Impact
- Threatened Species
- Social Impact
- Risk and Impact Factors
- Uses List
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Gaps in Knowledge/Research Needs
- Links to Websites
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Lepomis cyanellus Rafinesque, 1819
Preferred Common Name
- green sunfish
Other Scientific Names
- Apomotis cyanellus Rafinesque, 1819
- Chaenobryttus cyanellus Rafinesque, 1819
- Icthelus cyanella Rafinesque, 1819
- Lepidomus cyanellus Rafinesque, 1819
- Lepomis cyanella Rafinesque, 1819
- Lepomus cyanellus Rafinesque, 1819
- Telipomis cyanelus Rafinesque, 1819
International Common Names
- English: black perch; blue spotted sunfish; creek perch; goggle eye; green perch; mud bass; perch; pond perch; rice slick; ricefield slick; rubbertail; sand bass; shade perch; sunfish
Local Common Names
- China: Lan tai yang yu
- Denmark: gron solaborre
- Finland: viheraurinkoahven
- France: crapet vert
- Germany: grasbarsch; gruner sonnenbarsch; sonnenbarsch
- Netherlands: groene zonnebaars
- Norway: gron solabbor
- Spain: pez sol
- Sweden: gron solabborre
Summary of InvasivenessTop of page
Lepomis cyanellus is a perciform fish that is native to the central plains of North America, but has been introduced to most of the rest of the USA, and some other countries. Introduced L. cyanellus compete with and prey on native fish species, reducing their populations, altering their population structure, relative dominance and distribution patterns. Their aggressive nature allows them to compete with larger fish for prey, and prey on eggs and young of other fish species. L. cyanellus are remarkably tolerant of crowding under which conditions they are often stunted in size, creating management problems in small lakes. Large populations often compete with the young of other species for food, or prey upon them causing negative impacts to both game fish and native species. In streams where L. cyanellus have been introduced in California, it is believed to have helped deplete the California roach, Hesperoleucus symmetricus. L. cyanellus along with other predatory fish species is also thought to be responsible for the decline of native frogs and salamanders in the USA. L. cyanellus is listed as a major invasive species in parts of Arizona (USDA, 2012) and California (Dill and Cordone, 1997). New Jersey state authorities list it as a potentially dangerous species due to its ability to outcompete native fish species; it is listed as an invasive species of concern in Georgia and Florida. Marsh (2010), in a discussion on the advantages of genetic biocontrol in the Colorado River basin system, referred to the species as “one of the most invasive, pervasive, and destructive species in the basin, not even recognized as an invasive species by some states”. Olden and Poff (2005), in a study of long-term trends (> 160 years) of fish species distributions in the Lower Colorado River Basin, to identify those native species exhibiting the greatest rates of decline and those non-native species exhibiting the highest rates of spread, found that L. cyanellus was amongst the fastest expanding invaders in the basin and the most invasive in terms of negative impacts on native fish communities. As far as is known, L. cyanellus is not listed as a threatened species in any part of its native range.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Chordata
- Subphylum: Vertebrata
- Class: Actinopterygii
- Order: Perciformes
- Suborder: Percoidei
- Family: Centrarchidae
- Genus: Lepomis
- Species: Lepomis cyanellus
Notes on Taxonomy and NomenclatureTop of page
Lepomis cyanellus, or the green sunfish as it is commonly known, is a member of the Centrarchidae, the sunfish family. This family includes some of the more attractive and brightly coloured of the freshwater fishes of North America. The scientific name for the green sunfish is derived from the Latin Lepomis meaning “scaled operculum cover“, and cyanellus meaning “blue”.
DescriptionTop of page
Becker (1983) and Etnier and Starnes (2001) provide detailed descriptions of the anatomical features unique to L. cyanellus. It has an elongate laterally compressed body with a large mouth which extends beyond the broad anterior edge of the eye. The dorsal surface is brown to olive, with small scattered black flecks; the sides are of a lighter coloration, with females having 7-12 vertical bars (Etnier and Starnes, 2001). The two broad dorsal fins are joined, appearing as one; the first dorsal fin has 9-11 spines while the second has 10-12 soft rays. The pectoral fins are short and rounded. The anal fin has 3 spines and 9-10 soft rays, and the pelvic fin a single spine and 5 soft rays. The dorsal, anal and caudal fin margins of males are often bright yellow or orange. A dark spot is present at the rear of the dorsal and anal fins.
DistributionTop of page
L. cyanellus has a wide distribution range and is native to the central plains of North America between the Appalachian and Rocky Mountains, from Ontario (Canada) and New York state in the north to the Gulf Coast and northern Mexico in the south. It has been so widely introduced in the USA that it is now present in almost every state, including Atlantic and Pacific slope drainages and Hawaii, except for parts of the north-east of the country (Page and Burr, 1991). Populations are stronger within the native range.
According to Ma et al. (2003), L. cyanellus was introduced to China in 1999 for use as food; as far as is known, there have been no further reports on its status there. There is also little information on its presence in the Philippines, where it was introduced from the United States in 1950 for aquaculture purposes, apart from its being listed as present there by Halos et al. (2004). Although there are reports of an established population in Japan (Welcomme, 1988; Froese and Pauly, 2013), a survey by Mito and Uesugi (2004) on alien species recognised as established or present in the wild (as of 27 October 2004) does not mention L. cyanellus -- L. gibbosus is the only Lepomis species recorded.
There is some confusion as to whether L. cyanellus is present in Germany today. Maitland (1977) (cited in Soes et al., 2011) reported that its introduction by aquarists to the Frankfurt area led to established populations; this appears to contradict an earlier observation in 1959 by Sterba (as cited in Soes et al., 2011), that the species had disappeared from Europe. Lelek (as cited in Arnold, 1990) said there was no evidence for the presence of L. cyanellus in Germany. Elvira (2001), in a report identifying the non-native freshwater fishes established in Europe, lists L. cyanellus not only as an exotic freshwater species introduced to European waters but also as being present and established in Germany. The NOBANIS (European Network of Invasive Alien Species) website lists it as being established in Germany, and first recorded in 1965 (NOBANIS (2005), citing Geiter et al. (2002) (which Nehring (2005) also cites)). An ornamental fish stockist based in Germany lists the green sunfish on its website (www.aquarium_glaser.de) as being suitable for large cold water aquaria and garden ponds, adding that the specimens are German pond-bred and only occasionally found in the trade (Aquarium Glaser, 2013).
Attempts to introduce L. cyanellus in tropical Africa have been largely unsuccessful; where it has established itself, occupying smallish, well-vegetated dams and becoming over-populated, it is regarded a pest, according to Jackson (1976).
Lever (1996) reported the presence of naturalized populations of L. cyanellus in Germany (one population), Asia (2), Africa (4), Brazil (1), and Oceania (1).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
History of Introduction and SpreadTop of page
Expansion of the range of L. cyanellus in the United States has occurred mainly as a result of accidental stocking. It has been accidentally stocked as bluegill L. macrochirus, with other intended species as a stock contaminant (Dill and Cordone, 1997; USGS, 2013), as forage fish for smallmouth bass (Micropterus dolomieu) in fish farms, and as a sport or game fish. It has also escaped from holding ponds and spread of its own accord through stream channels and over flooded areas (Dill and Cordone, 1997) or via drainage ditches and irrigation waterways connecting river systems.
It has been introduced to other countries primarily as forage for black bass (Micropterus spp.) or for the purpose of aquaculture or sport fishing (Welcomme, 1988). Attempts to introduce it in tropical Africa have been largely unsuccessful; where it has established itself, occupying smallish, well-vegetated dams and becoming over-populated, it is regarded a pest, according to Jackson (1976).
According to Ma et al. (2003), L. cyanellus was introduced to China in 1999 for use as food; as far as is known, there have been no further reports on its status there. It was introduced to the Philippines from the USA in 1950 for aquaculture (Wellcome, 1988).
Maitland (1977) (cited in Soes et al., 2011) reported that the introduction of L. cyanellus by aquarists to the Frankfurt area in Germany led to established populations (Sterba (as cited in Soes et al., 2011) reported that the species had disappeared from Europe, but other sources indicate that it is still present there).
IntroductionsTop of page
Risk of IntroductionTop of page
The aggressive and predatory behaviour of L. cyanellus, and its ability to survive in a range of habitats and environmental extremes (low dissolved oxygen, high turbidity, alkalinity and siltation) indicate a high risk of spread and the potential to have a negative impact on native species. New connections such as drainage networks between lakes, rivers, ponds and streams, and flooding, enable its dispersal into water bodies well beyond its native range. Its use as a live bait fish also presents a risk of accidental introduction and subsequent establishment as in the case of the Great Lakes Basin (Mills et al., 1993; Litvak and Mandak, 1999).
HabitatTop of page
Tolerant of a wide range of habitats, L. cyanellus can be found in small muddy creeks, pools, streams, weedy backwaters with temporary flow to overflow ponds, shallow lakes, impoundments, ponds, springs, areas of rivers with little flow and sometimes the margins of large rivers of low gradient; it is highly adaptable, tending to become abundant in rocky areas of lakes or streams. It is commonly found near the shore and around cover such as stems of vegetation, rocks, or woody debris. Population abundance is positively correlated with percentage vegetative cover (Moyle and Nichols, 1973). It can tolerate turbidity, siltation, intermittent flow, high temperatures, high salt content and low dissolved oxygen. It tolerates crowding, often becoming stunted in size (Wellcome, 1988; Carlander, 1977), resulting in management problems in small lakes. Its aggressive nature allows it to quickly dominate wherever it is introduced, taking over in a very short period, and becoming the only species in a particular area, thus posing a major threat to native species (Etnier and Starnes, 2001). As a pioneering species, it is also the first species to find its way to newly created farm ponds and the first to repopulate streams following periods of drought (Tomelleri and Eberle, 1990; Pflieger, 1975, 1997). In northwestern Ontario it is found in habitats ranging from the shallow regions of moderately-sized lakes to small streams where it can be found in dense growths of vegetation (Crossman, 1976).
Although tolerant of poor conditions, it may prefer cleaner, larger, water bodies, with a moderate flow as growth has been observed to be greater in these areas than in more turbid waters or smaller streams and ponds (Carlander, 1977).
Habitat ListTop of page
|Lagoons||Principal habitat||Harmful (pest or invasive)|
|Irrigation channels||Principal habitat||Harmful (pest or invasive)|
|Irrigation channels||Principal habitat||Natural|
|Lakes||Principal habitat||Harmful (pest or invasive)|
|Ponds||Principal habitat||Harmful (pest or invasive)|
|Reservoirs||Principal habitat||Harmful (pest or invasive)|
|Rivers / streams||Principal habitat||Harmful (pest or invasive)|
|Rivers / streams||Principal habitat||Natural|
Biology and EcologyTop of page
L. cyanellus hybridizes with longear (L. megalotis), orange-spotted (L. humilis) and redbreast (L. auritus) sunfishes, bluegill (L. macrochirus), and pumpkinseed (L. gibbosus) (Scott and Crossman, 1973). Population genetic studies have been carried out on this species along with four other stream fishes (Husemann et al., 2012).
Age at maturation of L. cyanellus appears to vary depending on location; it has been reported at age one in Missouri, Illinois and Iowa, but not until age three in Michigan (Hubbs and Cooper, 1935; Sprugel, 1955). In Texas, sexual maturity is reached in less than 6 months (White, 1971). Males grow faster than females and appear to live longer (Carlander, 1977), with males and females maturing at minimum lengths of 45 and 66 mm, respectively. In Ontario, L. cyanellus live for 7 to 9 years and may grow to a length of 203 mm (Scott and Crossman, 1973). In Ohio, they may grow to 274 mm and weigh 400 g (Trautman, 1957). A Kansas specimen was recorded at 305 mm, weighing 964 g (Scott and Crossman, 1973). Carlander (1977) reported maximum age, length and weight of green sunfish of about 10 years, 276 mm and 408 g, respectively. In crowded conditions, the fish do not grow as well and stunting may occur (Carlander, 1977; Wellcome, 1988).
In the United States L. cyanellus spawn from late spring to early summer or April to August, when water temperatures range from 15 to 31°C. Spawning occurs from mid-May to early August in Wisconsin (Hunter, 1963) and from June to August in Illinois, Maryland, Michigan and Iowa (Carlander, 1977). There is no information on spawning in the Canadian part of the range, but on the basis of data from the USA, it is believed that it would probably occur in late spring to early summer in Canada as well. Peak spawning activity occurs at 20 to 28° C, and multiple spawnings occur every eight or nine days throughout the season (Hunter, 1963). Temperatures above 24°C for extended periods not only reduce nesting activity but may also stop spawning, and cause gonads to regress (Kaya, 1973).
The males are highly territorial and construct nests in colonies, in sunlit waters of 15 to 25 cm in depth, and sheltered by rocks, logs, clumps of vegetation and trunks (Carlander, 1977). They court females by rushing towards them and returning quickly to the nest. Hunter (1963) has described courtship and parental care in green sunfish in some detail. Females will lay from 2000 to 50 000 eggs (Carlander, 1977). Eggs are yellowish, adhesive, and 1.9 to 1.4 mm in diameter. Once eggs have been laid, the male guards and fans the eggs which hatch in 3 to 5 days (Scott and Crossman, 1973). The larvae are free swimming at 4.2 to 4.7 mm, within two days of hatching, and reach an average size of 23.7 mm by 57 days. Meyer (1970), Taubert (1977) and Auer (1982) have studied the eggs and larval development of green sunfish.
Trautman (1957) observed that growth of fry was rapid and young-of-the-year fish in Ohio reached lengths of 20 to 64 mm by October, and weights of 1.3 to 25 g. Increase in length of approximately 20 mm per year was achieved; no weight data were provided but in Wisconsin increases in weight varied from 10 to 42 g per year, with large increases in the fourth, fifth and sixth years (Carlander, 1977).
Physiology and Phenology
Of the centrarchids found in California, only juvenile L. cyanellus possess a chemical alarm signal similar to those found in cyprinids. When alarm pheromones, released due to mechanical damage to skin, are detected, they remain still with dorsal fins erect (Brown and Brennan, 2000).
In Ontario, L. cyanellus have been reported to live for 7 to 9 years (Scott and Crossman, 1973). Applegate et al. (1967) observed that in Bull Shoals reservoir in Arkansas and Missouri, they did not live beyond 6 years of age. In captivity, they lived to 7.5 years (Carlander, 1977). Wang (1986) reported them living 7 to 9 years in California, age at maturity being 1-2 years. Moyle (2002) reported a life span of 10 years with maturity at the beginning of the third year in Californian L. cyanellus.
Population Size and Density
L. cyanellus are remarkably tolerant of crowding, under which conditions they are often stunted, creating management problems in small lakes (Carlander, 1977; Wellcome, 1988).
L. cyanellus is highly predaceous, large populations competing with the young of other species for food or preying directly upon them (Minckley, 1973). Young feed on zooplankton (Carlander, 1977); fry subsequently eat aquatic insects and fish eggs while adults feed on fish eggs, snails, frogs, molluscs, insects and their young, crayfish, small fish and sometimes plant material (Struber et al., 1982). Adults have a larger mouth than most other sunfishes, and thus are able to swallow fish almost half the size of their own body; the adult diet consists of other small fishes and molluscs (Scott and Crossman, 1973). In Ontario, L. cyanellus is usually found in association with carp, Cyprinus carpio, and the smallmouth bass Micropterus dolomieu (Hallam, 1959), falling prey to both species as well as preying on their young. L. cyanellus have also been observed to feed on bryozoans (Fredericella sultana) (Applegate, 1966).
L. cyanellus is often found in association with other centrarchids, particularly the pumpkinseed (Lepomis gibbosus) and Longear Sunfish (L. megalotis) with which it is known to hybridize (Carlander, 1977). Hallam (1959), describing typical southwestern Ontario habitats for L. cyanellus in Canada, found that it inhabited areas frequented by rock bass (Ambloplites rupestris) and smallmouth bass (Micropterus dolomieu).
L. cyanellus is tolerant of a wide range of conditions. It is able to survive in both clear and turbid waters, although high species abundance is positively correlated with moderate (25-100 JTU) turbidities (Trautman, 1957). It is able to tolerate conditions of high turbidity <3500 JTU). Optimal dissolved oxygen requirements have been reported to be more than 5 mg/l (Petit, 1973), with lethal levels being less than or equal to 1.5 mg/l (Moore, 1942). Optimal pH range is believed to be from 6.5 to 8.5 (Stroud, 1967), with mortality occurring at pH £ 4.0 or ³ 10.35 (Ultsch, 1978). Green sunfish in Canada are reported to prefer a pH range of 6.0 to 9.6 and oxygen concentrations of 4 to 8 ppm (Meredith and Houston, 1988). Green sunfish will not tolerate salinities greater than 5.6 ppt (Kilby, 1955), optimal salinities being less than 3.6 ppt (Tebo and McCoy, 1964). Adults prefer 28.2°C, and when possible avoid temperatures above 31°C or below 26°C (Beitinger et al., 1975). There are reports of green sunfish in the field surviving in water temperatures as high as 36°C (Proffitt and Benda, 1971). Laboratory trials suggest that L. cyanellus, when properly acclimated, survives well at water temperatures near 1°C (Cortemeglia and Beitinger, 2008).
According to Childers (1967), optimal temperatures for spawning and successful development range from 20° to 27°C. Spawning will not occur below 19°C or above 31°C (Hunter, 1963). Optimal temperatures for fry range from 18° to 26°C (Coutant, 1977; T. Hardin and K. Bovee, US Fish and Wildlife Service, Instream Flow Group, Fort Collins, Colorado, USA, unpublished data, 1978, cited in Stuber et al., 1982); the range of temperature tolerance is reported to be 10-36°C.
Adults are found in low current velocity areas (Moyle and Nichols, 1973); preferred current velocities are below 10 cm/sec, while velocities of up to 25 cm/sec are tolerated (T. Hardin and K. Bovee, US Fish and Wildlife Service, Instream Flow Group, Fort Collins, Colorado, USA, unpublished data, 1978, cited in Stuber et al., 1982). Though tolerant of high turbidity, L. cyanellus is susceptible to heavy metals and nitrogen pollution, both common conditions in southwestern Ontario (Meredith and Houston, 1988). According to Meredith and Houston (1988), acid rain may have some influence on limiting populations in Ontario. Nests have been reported in polluted and channelized rivers and creeks, where dissolved oxygen levels were as low as 4 ppm (Wang, 1986; Wang and Reyes, 2008).
According to Cortemeglia and Beitinger (2008), the success of L. cyanellus in Great Plains streams and its widespread dispersion throughout North America may have been aided by its temperature tolerance ability.
Natural Food SourcesTop of page
|Food Source||Life Stage||Contribution to Total Food Intake (%)||Details|
ClimateTop of page
|Am - Tropical monsoon climate||Preferred||Tropical monsoon climate ( < 60mm precipitation driest month but > (100 - [total annual precipitation(mm}/25]))|
|B - Dry (arid and semi-arid)||Preferred||< 860mm precipitation annually|
|BW - Desert climate||Preferred||< 430mm annual precipitation|
|Cf - Warm temperate climate, wet all year||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year|
|Cs - Warm temperate climate with dry summer||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers|
|Cw - Warm temperate climate with dry winter||Preferred||Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)|
Water TolerancesTop of page
|Parameter||Minimum Value||Maximum Value||Typical Value||Status||Life Stage||Notes|
|Dissolved oxygen (mg/l)||5||Optimum||All Stages||Lethal levels less than or equal to 1.5 mg/l|
|Hardness (mg/l of Calcium Carbonate)||900||2000||Optimum||Adult|
|Salinity (part per thousand)||3.6||Optimum||All Stages||Up to 5.6 tolerated|
|Spawning temperature (ºC temperature)||19||31||Optimum||Broodstock|
|Turbidity (JTU turbidity)||25||100||Optimum||All Stages|
|Velocity (cm/h)||36000||Optimum||Adult||Up to 90 000 cm/h tolerated|
|Water pH (pH)||6.5||8.5||Optimum||Adult||Mortality may occur at pH less than or equal to 4.0 or pH greater than or equal to 10.35|
|Water temperature (ºC temperature)||28.2||Optimum||Adult||Where possible, avoids temperatures >31°C and below 26°C; reported to survive temperatures as high as 36°C and 38°C; spawning requires 19-31°C; tolerances for juveniles may vary|
|Water temperature (ºC temperature)||15||30||Optimum||Broodstock|
Natural enemiesTop of page
|Natural enemy||Type||Life stages||Specificity||References||Biological control in||Biological control on|
|Ameiurus||Predator||All Stages||not specific|
|Ictalurus punctatus||Predator||All Stages||not specific|
|Micropterus salmoides||Predator||All Stages||not specific||Morris and Mischke, 2000|
|Pylodictis olivaris||Predator||All Stages||not specific|
Means of Movement and DispersalTop of page
Accidental introductions of L. cyanellus can occur through the transportation and release of live bait by fishermen and anglers; increases in distribution of the green sunfish in the Great Lakes basin have been attributed to baitfish release (Mills et al., 1993; Litvak and Mandrak, 1999). Many unauthorized introductions of green sunfish across the United States were the result of authorized introductions of bluegill sunfish (L. macrochirus) or largemouth bass (Micropterus salmoides) using stocks which were contaminated with green sunfish (Benson, 1999).
In California, at the beginning of the 20th century, green sunfish were stocked in large numbers through the combined efforts of the California Division of Fish and Game and some sport fish clubs. Some of these green sunfish were raised in rearing ponds, and some were the result of fish rescue from overflow areas (Dill and Cordone, 1997). In 1944, the green sunfish was classified by the California Division of Fish and Game as an undesirable fish (compared with the bluegill) for stocking, although it retained its status as a "gamefish". Since that time it has been exterminated intentionally by the State in some trout waters. According to Dill and Cordone (1997), the introduction of the green sunfish to California was probably a mistake and that the waters of California would be better off without this species.
L. cyanellus were moved to Germany for the aquarium trade and to a number of other countries for aquaculture or as forage for other fish. Introduction to Korea is reported to have been ‘to fill a vacant niche’ (Welcomme, 1988).
Green sunfish have also expanded their distribution outside their native range via the waterways (stream channels, irrigation drainage systems, flooded areas) of the United States.
Pathway CausesTop of page
|Aquaculture||Introduced to the Congo, Zambia, Japan and the Philippines for aquaculture||Yes||Welcomme, 1988|
|Flooding and other natural disasters||Expanded its range to several US states||Yes||Yes||USGS, 2013|
|Forage||To Madagascar (1954), South Africa and Swaziland (1939), Zimbabwe (1940), and Brazil (1930s)||Yes||Welcomme, 1988|
|Hunting, angling, sport or racing||Introduced to Mauritius (1950) for sport||Yes||Welcomme, 1988|
|Intentional release||Release as live baitfish probably increased distribution in N. American Great Lakes basin||Yes||Yes||Litvak and Mandrak, 1999; Mills et al., 1993|
|Interbasin transfers||Expanded its range to several US states||Yes||Yes||USGS, 2013|
|Interconnected waterways||Expanded its range to several US states||Yes||Yes||USGS, 2013|
|Pet trade||Introduced to Germany by aquarists||Yes||Soes et al., 2011|
|Stocking||Expanded its eastward and westward range in the USA mainly due to accidental stocking||Yes||USGS, 2013|
Pathway VectorsTop of page
Impact SummaryTop of page
|Economic/livelihood||Positive and negative|
|Environment (generally)||Positive and negative|
|Fisheries / aquaculture||Positive|
Economic ImpactTop of page
L. cyanellus is problematic for fish management because it often outcompetes native fish.
This species has become an issue in bass-bluegill (Micropterus salmoides-Lepomis macrochirus) population management in the USA. Once introduced into a pond either by natural means (i.e. flooding) or by accident, green sunfish compete with small bass and bluegill; once established they have a tendency to overpopulate and limit food among the other game species present, especially if bass populations decline. They will feed on the eggs and young of bass, reducing bass numbers, and increasing their own numbers and thus the competition (Etnier and Starnes, 2001).
Although L. cyanellus is sometimes deliberately stocked for sport fishing, its high reproductive potential and tolerance for crowding lead to stunted populations which are unattractive to anglers. Precautions should be taken to prevent the introduction of green sunfish into ponds due to their ability to compete with other game fish, small size, and tendency to overpopulate (Etnier and Starnes, 2001).
Experiments on the use of the piscicide antimycin A to remove L. cyanellus from channel catfish (Ictalurus punctatus) production ponds showed that untreated ponds yielded 27.4% fewer catfish than treated ones, and three times as many catfish that were too small for table use (Burress and Luhning, 1969a).
Environmental ImpactTop of page
Impact on Biodiversity
Introduced L. cyanellus compete with and prey on native fish species, reducing their populations, altering their population structure, relative dominance and distribution patterns. Their aggressive nature allows them to compete with larger fish for prey, and prey on eggs and young of other fish species. Olden and Poff (2005), in a study of long-term trends (> 160 years) of fish species distributions in the Lower Colorado River Basin, to identify those native species exhibiting the greatest rates of decline and those non-native species exhibiting the highest rates of spread, found that the green sunfish was amongst the fastest expanding invaders in the basin and the most invasive in terms of negative impacts on native fish communities.
According to Moyle and Nichols (1973, 1974), L. cyanellus was responsible for the local extinction of the California roach (Hesperoleucus symmetricus) in California’s San Joaquin Valley as a result of heavy predation on its young. Lemly (1985) noted that the removal of green sunfish from streams resulted in an increase in the biomass and numbers of most native species. In a study of the North Carolina Piedmont streams, he found that green sunfish preyed on minnows and may have been responsible for the elimination of two cyprinid species in the study area.
Lohr and Fausch (1996) observed that L. cyanellus can reduce or eliminate plains killifish (Fundulus zebrinus) in isolated pools which may explain why both species rarely co-occur in isolated pools. Dudley and Matter (2000) found that young life phases of the Gila chubb (Gila intermedia) do not occur in downstream sections of the Sabino Creek in Arizona inhabited by green sunfish; abundant numbers of the young chubb were reported in upstream sections of the creek devoid of green sunfish. As the green sunfish feeds on all life stages of the Virgin River chubb, Gila seminuda, it is considered a threat to its existence (USFWS, 2013). According to Karp and Tyus (1990), the green sunfish may compete with and adversely affect the endangered young Colorado pikeminnow Ptychocheilus lucius.
In 2002, non-native L. cyanellus were documented for the first time in O’Donnell Creek, a tributary of the Babocomari River in southern Arizona; as a result, numbers of Sonora sucker (Catastomus insignis) and Gila chubb (Gila intermedia) decreased and longfin dace (Agosia chrysogaster) were extirpated. (Treatment with Antimycin A successfully removed all green sunfish). (Blasius, 2002; Clarkson and Marsh, 2010).
L. cyanellus and other introduced predatory centrarchids are also believed to have played a part in the decline of the California tiger salamander Ambystoma californiense in California (Hayes and Jennings, 1986; Dill and Cordone, 1997) and the Chiricahua leopard frog Rana chiricahuensis [Lithobates chiricahuensis] populations in southeastern Arizona (Rosen et al., 1995).
Threatened SpeciesTop of page
|Threatened Species||Conservation Status||Where Threatened||Mechanism||References||Notes|
|Ambystoma californiense (California tiger salamander)||VU (IUCN red list: Vulnerable) VU (IUCN red list: Vulnerable); USA ESA listing as endangered species USA ESA listing as endangered species||Arizona||Competition - monopolizing resources; Predation; Rapid growth||Dill and Cordone, 1997; Hayes and Jennings, 1986|
|Gila intermedia (Gila chub)||EN (IUCN red list: Endangered) EN (IUCN red list: Endangered); USA ESA listing as endangered species USA ESA listing as endangered species||Arizona||Competition - monopolizing resources; Predation; Rapid growth||Blasius, 2002; Dudley and Matter, 2000; USFWS, 2013|
|Gila seminuda (Virgin River chub)||EN (IUCN red list: Endangered) EN (IUCN red list: Endangered); National list(s) National list(s); USA ESA listing as endangered species USA ESA listing as endangered species||Arizona; Nevada; Utah||Predation; Rapid growth||USFWS, 2013|
|Hesperoleucus symmetricus||National list(s) National list(s)||California||Competition - monopolizing resources; Predation; Rapid growth||Moyle and Nichols, 1973; Moyle and Nichols, 1974; USFWS, 2013|
|Ptychocheilus lucius (Colorado pikeminnow)||No Details||Competition - monopolizing resources; Predation; Rapid growth||Karp and Tyus, 1990; USFWS, 2013|
|Rana chiricahuensis (Chiricahua leopard frog)||VU (IUCN red list: Vulnerable) VU (IUCN red list: Vulnerable)||California||Competition - monopolizing resources; Predation; Rapid growth||Rosen et al., 1995|
|Xyrauchen texanus (razorback sucker)||CR (IUCN red list: Critically endangered) CR (IUCN red list: Critically endangered); USA ESA listing as endangered species USA ESA listing as endangered species||Colorado||Competition - monopolizing resources; Predation; Rapid growth||Dudley and Matter, 2000; Marsh and Langhorst, 1988; USFWS, 2013|
Social ImpactTop of page
Although sometimes deliberately introduced for sport fishing, L. cyanellus often has a detrimental impact on populations of other more desirable species (Etnier and Starnes, 2001).
Risk and Impact FactorsTop of page Invasiveness
- Invasive in its native range
- Proved invasive outside its native range
- Has a broad native range
- Abundant in its native range
- Highly adaptable to different environments
- Is a habitat generalist
- Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
- Pioneering in disturbed areas
- Tolerant of shade
- Capable of securing and ingesting a wide range of food
- Highly mobile locally
- Long lived
- Fast growing
- Has high reproductive potential
- Altered trophic level
- Ecosystem change/ habitat alteration
- Negatively impacts aquaculture/fisheries
- Reduced native biodiversity
- Threat to/ loss of endangered species
- Threat to/ loss of native species
- Negatively impacts trade/international relations
- Competition - monopolizing resources
- Rapid growth
- Highly likely to be transported internationally accidentally
- Highly likely to be transported internationally deliberately
- Highly likely to be transported internationally illegally
- Difficult to identify/detect as a commodity contaminant
- Difficult to identify/detect in the field
UsesTop of page
Although L. cyanellus is barely suitable as a "pan-fish", and often thought not to be large enough to interest anglers, it can be exciting to catch; it is sought by recreational anglers in some US states (Wang, 1986; USFWS, 2002; Wang and Reyes, 2008). The fish have a tendency to attack almost any bait and provide a tough fight for anglers, given their size (Etnier and Starnes, 2001).
According to White (1971), the golden colour of Texas golden green sunfish (a colour mutation of L. cyanellus) could make it susceptible to predation and therefore a good forage fish. Biggins (1968) reported that the green sunfish was a major food source of largemouth bass, Micropterus salmoides, grown in a desert impoundment; Turner and Summerfelt (1971) also noted that it was a suitable food source for flathead catfish Pylodictis olivaris culture.
It is easily handled, making it a good bioassay specimen (Carlander, 1977).
Green sunfish are kept as aquarium fish by hobbyists in the USA, and possibly Germany and the Netherlands (Soes et al., 2011).
Uses ListTop of page
Animal feed, fodder, forage
- Fodder/animal feed
- Live feed
- Biological control
- Laboratory use
- Pet/aquarium trade
- Sport (hunting, shooting, fishing, racing)
- Sport fish
Human food and beverage
- Cured meat
- Fresh meat
- Live product for human consumption
- Meat/fat/offal/blood/bone (whole, cut, fresh, frozen, canned, cured, processed or smoked)
Detection and InspectionTop of page
L. cyanellus is easily identified by its large mouth, white- to orange-margined fins, and large dark spot at the base of the second dorsal fin; it can be distinguished from the bluegill L. macrochirus by its large mouth with the jaw extending to the middle of its eye and the lack of vertical bars. There is also a dark "ear" flap on the gill plate in green sunfish. It can be distinguished from the rock bass Ambloplites rupestris by the presence of 3 instead of 5-8 anal spines; its lack of an orange spot on the gill cover distinguishes it from the pumpkinseed L. gibbosus. Pflieger (1975, 1997) has provided details of a key to the identification of L. gulosus, L. cyanellus, L. microlophus, L. gibbosus, L. megalotis, and L. macrochirus.
Similarities to Other Species/ConditionsTop of page
L. cyanellus is similar to the warmouth, L. gulosus, the longear sunfish L. megalotis, and the bluegill L. macrochirus. It can, however be distinguished from these species by its large mouth, short, rounded pectoral fins, the three spines on its anal fin and its teeth-free pterygoids (Sublette et al., 1990). Unlike in the warmouth, there are no teeth on the tongue of the green sunfish. It only has 3 anal spines while the rock bass Ambloplites rupestris has 5-8 anal spines.
Prevention and ControlTop of page
Where L. cyanellus has been introduced as a result of an unauthorized fish introduction, a long-term solution would be through education of the public about the negative consequences of transferring fish to new water bodies. In the short term, legislation that makes unauthorized stocking illegal and the imposition of fines can serve as a deterrent. Where green sunfish are deemed a threat to other species in a system, the authorities may have to resort to removal by chemical or mechanical means. Articles in the popular press and in fishing magazines should highlight examples of illegal fish introductions; education can be done at the local level through news releases emphasizing the problems caused by an unauthorized introduction, or by distributing informational literature. Fisheries biologists should be able to suggest ways to humanely dispose of unwanted pet fish or unused baitfish as an alternative to releasing them into local waters (suggestions can be found at the US Geological Survey’s nonindigenous aquatic species information website, http://nas.er.usgs.gov/taxgroup/fish/)
L. cyanellus is difficult to control once it has become established in ponds. The entire fish population must be eliminated with chemicals or the pond drained to eliminate these fish. Sometimes it is possible to control numbers by continuous trapping, or by destroying spawning areas. The removal of vegetation cover will also expose L. cyanellus to predator fish species.
The use of antimycin A to remove unwanted L. cyanellus from channel catfish production ponds is well-documented (Burress and Luhning, 1969a, b). Green sunfish were effectively and economically controlled in channel catfish (Ictalurus punctatus) ponds on a Mississippi fish farm with antimycin A treatments. A follow-up application at a higher dose further reduced the green sunfish numbers with no apparent effect on yearling catfish. Untreated ponds yielded 27.4% fewer channel catfish than treated ponds and three times as many catfish that were too small for table use. Precise dosing of Antimycin A has also been used to remove green sunfish from live-haul tanks containing channel catfish following transport and prior to stocking of the latter in production ponds (Lloyd, 1987). This is because LC50 values established for green sunfish show they are 45 times more sensitive to antimycin than catfish (Finlayson et al. 2002). Green sunfish treated for 15 min with a range of doses died at concentrations well below those causing mortality in catfish (Finlayson et al., 2002). According to Lloyd (1987), removing green sunfish before stocking in production ponds results in lower costs and obviates the need for treatment of the entire pond at a later date.
A successful example of removal of L. cyanellus from a natural habitat using Antimycin A occurred in 2002, when the species was documented for the first time in O’Donnell Creek, a tributary of the Babocomari River in southern Arizona. As a result of their illegal introduction, numbers of Sonora sucker (Catastomus insignis) and Gila chubb (Gila intermedia) decreased and longfin dace (Agosia chrysogaster) were extirpated. To prevent extirpation of the Sonora sucker and Gila chubb, the authorities chemically renovated O’Donnell Creek in 2002 with Antimycin A to remove L. cyanellus; this led to their successful 100% removal (Blasius, 2002; Clarkson and Marsh, 2010).
A renovation project carried out in 1999 to remove L. cyanellus from Sabino Canyon (Pima County, Arizona) in an attempt to restore populations of Gila chub (Gila intermedia) was considered a success when repeated monitoring showed no signs of L. cyanellus following fish toxin application (Matter et al., 2001).
Gaps in Knowledge/Research NeedsTop of page
A survey of the status of L. cyanellus outside its native range would help to clear the confusion regarding its status where it has been introduced. Further surveys on its distribution in both its native and introduced range and its impact on native species would also be useful.
ReferencesTop of page
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ContributorsTop of page
Uma Sabapathy Allen
Human Sciences, CAB International, Wallingford, Oxon, OX10 8DE, UK
Distribution MapsTop of page
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