It scared you stiff, now the great white faces its own crisis

Sharks are history's survivors - they have been around far longer than dinosaurs, mammals, fish, reptiles or birds. Palaeontologists recently unearthed the jaws of a primitive shark that dated back 400 million years. But the silent cruising beasts could be on the way to oblivion, thanks to overfishing.

The great white shark. Its population has plummeted by 79 per cent.
© Keith Maywald/
WWF
Writing in the US journal Science, a team of scientists led by Julia Baum, of Dalhousie University in Halifax, Nova Scotia, reveal the results of an analysis of the logbooks of American long-line fleets that hunt tuna and swordfish in the Caribbean, the Gulf of Mexico, the Florida coast, the Sargasso sea and the north central Atlantic. Long lines carry up to 550 hooks apiece and logbooks should record sharks that are also caught.

"We estimate that all recorded shark species, with the exception of makos, have declined by more than 50 per cent in the last eight to 15 years," the scientists report. They warn that existing measures to save species, including planned marine reserves, will not be enough to halt the decline of the threatened species. The existing protection for other large marine predators, such as sea turtles and tuna, should be extended to sharks as well.

Their research confirms a growing overall picture, on both sides of the Atlantic, of mounting problems for marine predators. The Atlantic halibut has all but disappeared in many areas, while pelagic fish in some waters have been reduced to 15 per cent of what were healthy populations. Just as big cat numbers provide a clue to the diversity of life in the forests and savannahs, shark numbers provide a snapshot of life in the deep.

"Sharks are one of the best natural barometers to indicate the health of our seas and oceans. If sharks do not exist it spells bad news," said Ian Fergusson, of the International Union for the Conservation of Nature.

Sharks, skates and rays are all elasmobranchs, as distinct from bony fishes. They take a long time to mature, and produce few young. Once a population starts to decline, it becomes vulnerable to extinction because adults disappear before they can replace themselves.

But the catch, for researchers, is that the Atlantic is huge, deep and opaque. They must use indirect ways to monitor shark populations. The fishing fleets' logbooks provided the only consistent data of shark numbers year by year. These logbooks told an alarming story, revealing that the most pronounced decline was in the ham merhead population, which had dropped by 89 per cent since 1986.

White sharks - the great white shark was the villain of Steven Spielberg's thriller Jaws, and is one of the few species known to attack humans - showed an estimated 79 per cent decline. In some areas, no white sharks had been reported for a decade. Tiger shark catch rates fell by an estimated 65 per cent, and thresher sharks by 80 per cent. Blue shark populations had fallen by 60 per cent, and the oceanic whitetip shark by an estimated 70 per cent.

This is part of a much larger picture of accelerating extinction rates. A quarter of all mammals and at least one bird species in eight are threatened with extinction because of human activity. Up to 30 per cent of terrestrial plants are also at risk.

• Meanwhile The Observer reports (19 January 2003) that dolphins off the South West coast of England are in danger of being wiped out. So far this year 54 dolphins have been found on the shores of Devon and Cornwall. Laila Sadler of the Royal Society for the Protection of Animals warns that the death toll could be as high as 10,000 a year. Increasing numbers are being killed after getting caught in huge fishing nets used by trawlers. Once ensared, these graceful creatures don't stand a chance. Often their beaks will be broken and their flippers torn off as they attempt to break through the industrial strength plastic mesh.
  

Tim Radford is Science Editor for The Guardian.

This is a shortened version of an article which first appeared in The Guardian, (Friday January 17 2003). All rights reserved. Reproduced with kind permission.

Related articles and links:

Sharks in the soup

Dirty driftnet fishing continues in European waters

The dolphins are dying

Shark Trust

Science magazine

Whale and Dolphin Conservation Society

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