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Big fish of the seas face extinction
By Roger Highfield, Science Editor
(Filed: 15/05/2003)

The world's fisheries are in a far worse state than anyone realised: 90 per cent of large fish have disappeared in the past half century, according to research that suggests that the bigger fish - large tuna, sharks, swordfish and even cod - may soon be merely memories.

Industrial fishing methods can take as little as a decade to grind any new fish community they encounter to one tenth of what it was before, according to a 10-year study of the archives that provides the first insight into the devastation caused by 50 years of over-fishing.

The average size of top ocean predators - such as the blue marlin - is only a fifth to one half of what it used to be, says the study, published in Nature.

The Canadian scientists say that if the world's oceans are to recover, fishing mortality should be cut by up to half by reducing quotas, overall fishing effort, subsidies, bycatch and by creating networks of marine reserves. These measures will cause fishermen short term pain - but will ensure long term gain.

The researchers show that, compared with 1950, we now have only 10 per cent of all large fish - both open ocean species including tuna, swordfish, marlin and the large groundfish such as cod, halibut, skate and flounder - left in the sea.

"Since 1950, with the onset of industrialised fisheries, we have rapidly reduced the resource base to less than 10 per cent - not just in some areas, not just for some stocks, but for entire communities of these large fish species from the tropics to the poles," said the lead author Prof Ransom Myers of Dalhousie University in Canada.

Most surprising is the decline in open ocean where people have presumed that there are still untapped reservoirs of big fish.

To measure this decline, the researchers used data from Japanese longline fleets, which catch a wide range of species in a consistent way over vast areas. "Whereas longlines used to catch 10 fish per 100 hooks, now they are lucky to catch one," said Prof Myers.


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