(This article was originally published on OceanLines on August 15, 2008.)
The shark species in the Mediterranean Sea have continued to decline severely over the last two centuries. Over that period some species have declined by over 99%, according to historical records. The decline is due mostly to fishing. Data has been gathered from old fishermen’s notes and archive records in order to prove the decline and plot the trends for the five top predators.
“Sharks have never been managed – they slipped under the radar” says Rebecca Greenberg, a marine scientist from Oceana. Sharks, and their cousins, the rays, are very vulnerable to over-fishing because they mature slowly and don’t reproduce until much later in life.
According to records, fishermen consider sharks to be pests. And who cares if pests are killed? “They were caught as bycatch by boats chasing important species such as tuna – so they were declining without anyone noticing” says Francesco Ferretti who has been working with the Lenfest Ocean Program in the Mediterranean from Dalhousie University in Halifax, Canada.
In the Mediterranean there are 47 shark species that can be found there regularly, 20 of which are top predators. For 5 of these top predators records, from commercial boats and tuna traps, were substantial enough to conclude that catches were responsible for the decline in the population.
The hammerhead shark population has declined by more than 99.99% over the last two centuries. In the last century, or so, they have virtually disappeared from coastal waters and recently, within the last 20 years, have seemed to disappear in pelagic zones as well. Two species of mackerel sharks and the blue shark have also seemed to vanish from coastal areas, and while the thresher is still occasionally caught in tuna traps, their numbers have also declined by 99.99%. As for the other 15 top predators, records were not sufficient enough to plot data, although declines are obvious.
Ferretti hopes that this study will “contribute to a greater threat status for hammerheads and blue sharks, and other assessments in the Mediterranean.” Conservation groups feel that a strict set of measurements to protect sharks worldwide is not only necessary, but long overdue. The protection would include setting global catch limits, banning finning, and implementing measures to reduce bycatch.
Copyright © 2008 by OceanLines