Taxonomic name: Morone americana (Gmelin, 1789)
Synonyms: Morone americanus (Gmelin, 1789) , Morone pallida Mitchill, 1814 , Morone rufa Mitchill, 1814, Perca americana Gmelin, 1789 , Perca immaculata Walbaum, 1792 , Roccus americanus (Gmelin, 1789)
Common names: Amerikanbassi (Finland), Amerikansk bars (Denmark), bar blanc d'Amerique (France), baret can (France), bars (Denmark), cernier atlantique (France), havabbor (Norway), hvit havabbor (Norway), morona (Russian), narrow-mouthed bass, perche blanche (France), robalo do norte (Portugal), robalo-do-norte (Portugal), rokiel srebrzysty (Poland), sea perch, seebarsch (Germany), silver perch (English), spigola americana (Italy), vitabborre (Sweden), White perch (English), wreckfish (English)
Organism type: fish
Morone americana is a semi-anadromous fish native the Atlantic Coast, that has made its way into the Great Lakes through the Erie and Welland canals. Dense Morone americana populations compete for food and feed on the eggs of native species. Hybridisation with other perch species is another threat that may cause dilution to local species gene pools.
Morone americana is a semi-anadromous fish that in its native range migrates from the saltier areas of bays and coastland into tidal-fresh portions of streams and rivers to spawn in spring. M. americana usually reach a length of 127-178mm and can weight from 250g on average to a record of 650g. The colouring of this species is variable from dark grayish-green, dark silvery green, or dark brown to almost black on back; pale olive or silvery green on sides; silvery white on belly. Other identifying characteristics include: The body is deepest just ahead of, or at the beginning of, the dorsal fin; There are no lines or stripes on the back or sides; When the spiny dorsal fin is pulled erect, the soft dorsal fin also becomes erect; The second and third bony anal spines are almost exactly the same length; and The anal fin usually has 8 or 9 soft rays behind the 3 bony spines (Chesapeake Bay Program, 2006; National Sea Grant, 1998; and Wisconsin Sea Grant, 2002).
coastland, lakes, marine habitats, water courses
Their native range is the Atlantic Slope drainages from St. Lawrence-Lake Ontario drainage in Quebec south to the Peedee River of South Carolina. They have now become very common in shallow portions of inland lakes and rivers (Minnesota Sea Grant 2001; and Wisconsin Sea Grant, 2002).
Morone americana compete for food with native fish species and also eat the eggs of walleye (Stizostedion vitreum), white bass (Morone chrysops), other M. americana and possibly other species as well. They are also believed to be a potential cause of decline in S. vitreum populations. Another concern is that M. americana have hybridized with native Morone chrysops in western Lake Erie. Hybrids are capable of backcrossing with parent species as well as crossing among themselves and could dilute the gene pool of both parent species (Fuller et al. 2006).
Fish eggs are an important diet component in the spring. Depending on which fish is spawning, the eggs of either walleye or white bass comprise 100% of M. americana's diet. Collapse in certain fisheries have coincided with increases in M. americana populations and are believed to be a result of egg predation and resulting lack of recruitment (Fuller et al. 2006).
An excellent panfish highly regarded as a food fish in the Eastern United States, it is not often exploited as a game fish and generally is regarded as undesirable, especially when over-population in fresh waters causes the species to become stunted (Wisconsin Sea Grant, 2002).
In the Chesapeake Bay, there is increasing concern about toxic materials, like Polychlorinated Biphenyls (PCBs). Scientists assess PCB concentrations in local M. americana. This species is a good indicator of toxic contaminant concentrations in the Bay's waters because they are a resident species in the Bay. Data gathered from Maryland and Virginia suggests that PCB concentrations are higher among M. americanain the upper Bay than they are in the lower Bay. Similarly, there is a trend in fish tissue where fish on the eastern shore have lower concentrations of PCBs than their counterparts on the western shore. A common characteristic among the areas of the Bay where M. americana have higher PCB concentrations is related to land development; the western shore of the Bay is more developed than the eastern shore of the Bay, and M. americana from the Bay's western shore have higher PCB concentrations than their counterparts on the eastern shore (Chesapeake Bay Program, 2006).
Native range: North America’s Atlantic Slope drainages from St. Lawrence-Lake Ontario drainage, Quebec, south to Pee Dee River, South Carolina (Fuller et al. 2006).
Known introduced range: USA (Colorado, Illinois, Indiana, Iowa, Kansas, Maine, Massachusetts, Michigan, Minnesota, Missouri, Nebraska, New Hampshire, New York, Ohio, Oklahoma, Pennsylvania, Vermont, Virginia, West Virginia, Wisconsin) (Fuller et al. 2006).
Fish eggs are an important component of the diet of Morone americana especially in the spring months and this species will even cannibalize its own eggs. Walleye or white bass eggs can make up 100% of M. americana diet depending on which fish is spawning. M. americana also feed heavily on minnows of Notropis spp. and zooplankton (Fuller, 2005).
Males may spawn for the first time at age 2, females usually by age 3. These fish usually spawn in late spring in brackish to nearly fresh water rivers over sandy bottoms. When spawning females release between 50,000 and 150,000 eggs over a period of 10 to 21 days; several males may hover around a single female as she spawns to fertilize her eggs; and hatching takes place between 1 and 6 days following fertilization. Young M. americana use near shore areas downstream from their hatching areas to feed on the larvae of insects and crustaceans during their first summer and fall seasons. Mature M. americana may remain in quiet tributaries throughout spring and summer, or venture into open waters; in winter; however, adults swim downstream to the deeper channels. M. americana may live up to around 10 years, feeding on small fish and shellfish, and other bottom-dwelling aquatic species (Chesapeake Bay Program, 2006).
Reviewed by: Pam Fuller USGS/BRD Nonindigenous Aquatic Species Program Florida Integrated Science Center Gainesville, Florida USA
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Friday, 27 October 2006