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Description

Salmo trutta is called the Brown trout because of its brown to gold-brown colorations. The sides of the fish are yellow or silvery and the bellies can be white to yellow. Red spots with blue outer-circles and plain black spots are apparent in the stream-dwelling brown trout; but faint on the ones found in lakes. There are two dorsal fins, with the rear one being a reddish, fat-filled fin. The anal fin has 9-10 rays and the tail is square. Adults in the United Kingdom can be 13-16 inches long and weigh up to 10 pounds.

Ecological Threat

Brown trout may compete with other native trout and salmon species for food. They grow larger and faster than native species and have been reported to reduce trout populations by predation. As aggressive defenders of territories, they can displace native fishes from prime habitat. They have been implicated in population reductions of the brook trout (Salvelinus fontinalis) and Modo sucker (Catostomus microps) which is an endangered fish in California. Also, even though it is rare, the brown trout can hybridize with native trout species and can then reduce native trout populations. Brown trout has been nominated as one of the “100 of the ‘World’s Worst’ invasive alien species” by the IUCN and Global Invasive Species Programme.

Biology

Brown trout spawn from October to December in shallow (1 ft. deep) headwater streams. The female hollows out a redd (nest), in which to release her eggs. As she does this, the male released his milt to fertilize them. The female covers the fertilized eggs with sand and fine gravel, and both adults leave. The larvae stay in the redd for 2-3 weeks until they are about .1 inch long. They them move downstream or into lakes for the first two years of their life. Brown trout establish their territories when they are juveniles and mature 3-4 years of age.

History

Salmo trutta eggs were first imported from German hatcheries into the United States in 1883 to Cold Spring Harbor, New York. The eggs were then distributed to the Norville Hatchery in Michigan. In 1886, Pennsylvania began stocking the fish in streams where native brook trout populations had been severely decreased by logging, farming and dam construction. Since then, brown trout have been stocked by local and state agencies across the country for sport fishing.

Native Origin

Native Origin: Seas of Eurasia; including Baltic, Caspian, Black and Atlantic Ocean

Current Location

U.S. Habitat: In the United States, brown trout are found in freshwater streams and lakes. They hide during the day in aquatic vegetation and prefer water temperatures ranging from 65^o-75^o and can tolerate warmer temperatures that the native brook trout.

U.S. Present: Introduced into all 50 states and Puerto Rico, but AK, LA and MS do not have established populations.

Management

Since this fish is regularly stocked by local and state agencies as a sport fish it is not able to be manage. Now sport fishing of these salmonids can help reduce the annually replenished populations. But until this fish is actually removed as a sport fish it will be nearly impossible to control. In New York, programs aimed at improving water quality for native brook trout are also now control methods for the brown trout. In California, attempts are being made to eliminate brown trout where they may compete with golden trout (Oncorhynchus mykiss aquabonita).

References

Text References

Diamond, S. E. 2012. Mechanisms and consequences of hybridisation between Atlantic salmon (Salmo salar) and brown trout (Salmo trutta).

Fausch, K. D., & White, R. J. 1981. Competition between brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta) for positions in a Michigan stream. Canadian Journal of Fisheries and Aquatic Sciences, 38(10):1220-1227.

Garman, G. C., & Nielsen, L. A. 1982. Piscivority by stocked brown trout (Salmo trutta) and its impact on the nongame fish community of Bottom Creek, Virginia. Canadian Journal of Fisheries and Aquatic Sciences, 39(6):862-869.

Simberloff, D. 2010. Box 7.1 Native invasives. Conservation Biology for All, 131.

Witmer, G. W., & Fuller, P. L. 2011. Vertebrate species introductions in the United States and its territories. Current Zoology, 57:559-567.

Woodward, Susan L., and Joyce Ann. Quinn. 2011. Brown Trout. Encyclopedia of Invasive Species: From Africanized Honey Bees to Zebra Mussels. Santa Barbara, CA: Greenwood, 166-67. Print.

Internet Sources

http://www.michigan.gov/dnr/0,4570,7-153-10364_18958-45650--,00.html

http://www.issg.org/database/species/ecology.asp?si=78

http://www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Salmo_trutta.htm

http://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=931