Review of the Article on Cascading Effects of the Loss of Apex Predatory Sharks from a Coastal Ocean

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Jennifer Lin
BIEB 132 paper 2
11/6/2008

Article: Cascading Effects of the Loss of Apex Predatory Sharks from a Coastal Ocean By Ranson A. Myers et. al

Apex predators are the organisms on the top of the trophic level in the ecosystem. It often plays a crucial role in the balance of the overall trophic relationship between species because the relationship of one species feeding on the other or is consumed by another species closely associate each other. The removal of one species in the particular food chain can be devastating to all the species involved in the food chain. In this paper, the great shark is an example of a type of apex predator because it is the species that plays a role as feeding other species that exist lower in this food chain. The functional groups are the species associate in the food chain and all of their existence are crucial to the food web. The main species that play a part in the food chain are the great sharks (apex predator), elasmobranchs (these are the mesopredators; for example the rays and specifically the cownose ray in this article, skates, and small sharks) and the bay scallop. The cascading top-down effect in marine ecosystem illustrates the effect of the change in the apex predator will eventually affect the other species that are lower in the food chain. In the article, the removal of great sharks due to the high demand of shark fins and meat in the food chain causes increase in the population of the elasmobranchs. The specific example of the elasmobranchs, the cownose rays which are feed on the bay scallop causes the shutdown of scallop fisheries due to the over abundance in cownose rays. This effect is exhibit when the top-down control becomes weakened.

In the western Atlantic, the great sharks which are the apex predators have highly decreased in number in recent years due to overexploitation of the high demand in shark fins and meat causing mesopredaotors to increase abundantly and forced the scallop...
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