The predators of the oceans have become preys themselves. Sharks head the chains of the oceanic food web, there depletion has led to the destruction of the bay scallop fishery along parts of the Eastern seaboard and other species including shrimp and crabs are also threatened.
The study, by Ransom A. Myers of Dalhousie University in Halifax, Nova Scotia, and colleagues, is among the few to document the cascading effects that the loss of a top predator can have on a marine ecosystem. In the absence of large sharks, the researchers say, the smaller sharks, skates and rays that they feed upon have thrived.
In turn, the study shows that as one of these middle links in the food chain, the cownose ray, has become more abundant, it has wiped out scallop beds in North Carolina. Bull, dusky and hammerhead sharks have declined by more than 99 percent between 1970 and 2005.Shark fins currently sell for about $22 a pound. They are in great demand for medicinal purposes.
Now that the ravenous rays and skates have feasted on bay scallops, they are likely to look for food in protected areas along the coast where other fish and shellfish shelter in their early months of life. Overfishing of any species is a bane on the marine ecosystem.