Fishing takes big bite out of shark population

Fishing takes big bite out of shark population
5:00AM Friday June 13, 2008

The number of sharks in the Mediterranean has fallen by 97 per cent in the past 200 years, putting the sea's ecological balance at risk, a report says.

The Washington-based Lenfest Ocean Programme report used records such as fishermen's logs, shark landings, museum specimens and visual sightings to estimate the number and size of the Mediterranean sharks during the past two centuries.

Of the 20 big shark species in the Mediterranean, there was only enough data to research five - the hammerhead, thresher, blue and two species of mackerel shark - which averaged a decline of 97 per cent.

"It will have a major impact on the ecosystem because large predatory sharks are at the top of the food chain," said Francesco Ferretti, the report's lead author.

Without the top of the food chain, smaller fish can thrive and consume more of their prey, upsetting the ecological balance.

"If we lose these sharks we are going to lose this important portion of the ecosystem functioning," said Ferretti.

A report last month by the International Union for Conservation of Nature found 11 kinds of shark faced extinction due to over-fishing, partly caused by booming demand for shark fin soup in Asia.

Fishermen from all over the world trade sharks for their fins, often discarding their carcasses, the report says, noting Indonesia and Spain are among the top culprits.

Ferretti said this practice was thought to be uncommon in the Mediterranean due to the small numbers of sharks. More of a problem was "by-catch" - sharks caught in long-line fishing meant to snag tuna and swordfish.

"The Mediterranean has been fished since Roman times, it's a historical thing," said Ferretti. "But now [modern] fishing has a big impact on the shark population."

UNDER THREAT
* There are 47 species of shark found regularly in the Mediterranean. Twenty of them are top predators.
* For five of the 20 top predators, records during the past 200 years were good enough to indicate their numbers have declined, on average, by 97 per cent.
* The hammerhead and thresher populations are believed to have fallen by more than 99.99 per cent.