OVERFISHING is sending cod stocks in the North Sea the way of the
Canadian Grand Banks fishery, which collapsed four years ago and as yet shows
little sign of recovery.
鈥淎t present exploitation rates, only four per cent of fish aged one will
survive to the age of four鈥�, the age at which they mature, warns a team led by
Robin Cook of the Scottish Office鈥檚 Marine Laboratory in Aberdeen in a paper in
this week鈥檚 Nature. A detailed modelling exercise by Cook and
colleagues from Canada and Iceland predicts that 鈥渨ithout a substantial
reduction in the rate of fishing, the North Sea cod stock may well
肠辞濒濒补辫蝉别鈥�.
The scientists believe that the European Union鈥檚 attempts under the Common
Fisheries Policy to reduce the total allowable catch (TAC) for 1997 will not
work. 鈥淔ishermen find a way round these rules,鈥� says one of the authors.
鈥淲hatever the limits, our experience is that they always seem to take about 60
per cent of the cod in any one year. That needs to come down to a maximum of 40
per cent.鈥�
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The International Council for the Exploration of the Seas, a group of
fisheries scientists whose data was used by Cook, says that restricting the
number of days fishing boats can put to sea would reduce catches more
effectively than TACs.
Cook used a model that calculates the sustainable yield of a fishery by
plotting the natural relationship between birth and death rates among the fish
against different fishing rates. The model itself is not new, but it produced
alarming predictions when Cook applied it to the latest data on the North Sea
cod stock.
In December the European Commission backed away from imposing severe cuts in
fishing quotas, accepting that stocks had recovered in some areas because of
good weather. But Cook says that this 鈥渄oesn鈥檛 change the overall picture
of over-exploitation鈥�. And he warns that, given the the model鈥檚 inbuilt
uncertainties, even fishing at close to the theoretical maximum sustainable
yield could be dangerous. Even a small increase in catch above the maximum yield
causes the fish stock in the model to spiral into catastrophic decline.
The scientists鈥� comparison to the Canadian Grand Banks cod fishery will alarm
conservationists and the fishing industry. Cod stocks there collapsed, and the
fishery has been totally shut down since 1993, with the loss of 40 000 jobs.
鈥淪igns of recovery of the stock are still very small, and in fact some stocks
still seem to be in decline,鈥� says Cook鈥檚 coauthor, Alan Sinclair of the
Canadian government鈥檚 fisheries department.
This public warning from government fisheries scientists follows stinging
criticism from the House of Lords science and technology committee a year ago
(This Week, 10 February 1996, p4). The committee called for biologists to give
firm advice 鈥渋n a form which the political managers could not ignore鈥�. Singling
out the risks to North Sea cod, committee chairman Lord Selborne said that
caution about the accuracy of their models was 鈥減roviding an excuse for
political compromise鈥�.