Species Depletion Essay

Species Depletion Essay





An exotic species is a species with the ability of propagating that species in the habitat that is not native. Introduction of an invasive species in an ecosystem where it is not native leads to either economic or environmental harm. This invasion involves environmental boundaries. Since 1800 more than 25 exotic species of fish have entered the popular great lakes. These nonnative breeds of fish have a momentous impact on the food web in the great lakes. This is because they compete for habitat and food with others CITATION Joh93 l 1033 (Hartig & Commission, 1993). They are also responsible for degradation of wetlands in the coast leading to plant cover loss. It also leads to changing the natural habitat which the native species depend on.

Overfishing and introduction of exotic fish species for biological control and sport is evident. The zebra mussel for instance filters algae which provide the native fish with very valuable nutrients when it is in the water. These nutrients end up at the lake bed leading to an environment favorable for aquatic plants CITATION Bio01 l 1033 (Program, 2001). This compromises the prized walleye fish because they prefer cloudy water for both their defense and hunting.

The alewife invasion for instance Michigan and Huron lakes have suffered a lot of depletion of the native ciscoes. This has resulted in the species’ diversity in those lakes which are now dominated by alewife, bloaters and sculpins CITATION Joh93 l 1033 (Hartig & Commission, 1993). Lake Walleye, lake trout and sturgeon have are all victims of displacement. One of the lakes called trout was extinct.

Presence of sea lamprey has been noted in Lake Ontario since 1835. It entered through Wellend canal then penetrated to Lake Erie way back in 1921. It was discovered in Lake Michigan a decade later then it spread to Lake Huron. The sea lamprey had made its way in all great lakes, killing the thriving fish industry. Full restoration of the great Lakes into the original conditions is not possible considering the mass biotic changes resulting from exotic species invasion. Controlling its spreading to the neighboring waters is not practical CITATION Joh93 l 1033 (Hartig & Commission, 1993).

The ecological management objectives of these lakes should be preventing introduction of new exotic in the Great Lakes. One defense mechanism against fish species that invade is building of electric gates in the canals that feed the great Lakes CITATION Bio01 l 1033 (Program, 2001). They should also seek to understand the natural ecosystem and closely monitor all vessels to curb the invasion in the future. However, some of the exotic species can be eradicated by the rapid response action possible when the species is detected early enough. Management and control of such a species follows if the species cannot be completely eradicated. This should be done using an environmentally friendly method.

Conservation of fish in the United States is done by the “fish and wildlife service” which has the responsibility of conserving not just fish but also plants and another aquatic life. It has a very crucial role because the invasive species cause a lot of degradation of the natural habitat as well as competing with the native fish and other aquatic animals for shelter, food and space.

If the aquatic species are not given special attention, they are at a risk of becoming extinct. A report by Nature Conservancy shows that almost forty percent of fresh water fish are at a risk of becoming extinct. Also, more than fifty percent of crayfish in the United States have been jeopardized.


BIBLIOGRAPHY l 1033 Hartig, J. H., & Commission, G. L. (1993). A survey of fish-community and habitat goals/objectives/targets and status in Great Lakes areas of concern. New York: Great Lakes Fishery Commission.

Program, B. S. (2001). Biodiversity Support Program : a consortium of World Wildlife Fund, the Nature Conservancy, and World Resources Institute funded by the US Agency for International Development. Washington D.C: World Wildlife Fund.

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