Sunday, June 22, 2008


Rome: A new scientific study funded in part by the Lenfest Ocean Program has concluded that all shark species assessed in the Mediterranean Sea have declined by more than 97 percent in abundance and “catch weight” over the last 200 years.
The findings of the study, Loss of large predatory sharks from the Mediterranean Sea, published in the journal Conservation Biology, suggest several Mediterranean shark species are at risk of extinction, especially if current levels of fishing pressure continue. There used to be 47 species of Shark in the Mediterranean, of which 20 were considered "top predators". Now, some of the big Sharks are virtually extinct.

Hammerhead Sharks have declined the fastest, with no recorded sightings in the Mediterranean since 1995. Hammerheads are estimated to have declined by 99.99%
Blue Sharks have declined by 96.53% in abundance and by by 99.83% in biomass in the last 50 years, with the steepest decline in the waters around Spain
The two Mackerel Sharks (Porbeagle and Shortfin Mako) have declined by more than 99.99% in both abundance and biomass over the last 100 years.
Thresher Sharks are the only species detected in coastal waters in recent times. Threshers have nonetheless declined by more than 99.99% over the last 100 years.
"Usually at the apex of trophic chains, large sharks are expected to play an important role in the structure and functioning of marine ecosystems .
Thus, the decline of large sharks may have marked ecological consequences. In the Gulf of Mexico predator and competitor release effects have been evident after the depletion of large sharks . In the northwestern Atlantic the decline of great sharks from coastal ecosystems has triggered a trophic cascade that collapsed a century-old fishery for bay scallops. Moreover, food-web models from the Caribbean suggest that large predatory sharks are among the most strongly interacting species, and that their overfishing may have caused trophic cascades that contributed to the degradation of Caribbean ecosystems ."

"Our analysis, combined with previously published information, indicates that the Mediterranean Sea is losing a wide range of its predator species. In addition to large predatory sharks, cetaceans, pinnipeds, turtles, and large bony fishes have declined similarly.
The wider ecosystem consequences remain to be investigated. Nevertheless, in various other systems, it has been demonstrated that predators can play an important role in structuring communities by controlling prey populations and preventing ecological dominance. Losing top predators can induce strong increases in midlevel consumers, shifts in species interactions, and trophic cascades."

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