The message from researchers about the state of European fish stocks is consistent, but its delivery could be improved.
It is the same procedure every year: based on the advice of fisheries biologists across Europe, the International Council for the Exploration of the Sea (ICES) has again recommended a ban on cod fishing in the North Sea, the Irish Sea and west of Scotland.
As usual, the advice is likely to fuel a public outcry in the regions where fishermen live. And the European Union (EU), which sets annual catch quotas for fish, must walk a fine line between conserving the short-term future of the fisheries industry and the long-term survival of fish stocks. This annual event has already driven a wedge between scientists and fishing communities, a bad starting point for addressing the problem of fisheries conservation. Not only do fishing communities tend to dig in their heels, but conservationists sometimes exaggerate the need for draconian reductions in quotas.
Marine biologists often disagree over the best ways to conserve declining fish stocks worldwide (see Nature 419, 662–665; 2002). And it isn't certain that fishing for threatened species — such as European cod — has to stop entirely, if stocks are to recover. This year, for example, cod stocks in the North Sea appear to have bounced back up by almost one-third, albeit from a worryingly low estimate of 35,000 tonnes, despite the fact that some fishing is permitted. ICES thinks that no fishing should be allowed until stocks reach 150,000 tonnes.
But fish population dynamics is an uncertain business. Biologists' models don't work well if the stock in question is small, as is the case with European cod. Fish populations can fluctuate enormously from one generation to the next, depending on environmental conditions such as the weather, ocean turbulence and plankton availability. If the hydrographical conditions are favourable next season, cod stocks may recover further — but they could just as easily collapse. So from a precautionary point of view, it is understandable that scientists recommend fishing bans, even though they don't know for sure that continued fishing will wipe out European cod.
Such uncertainty does not release the EU from its obligation to optimize fisheries management. It can't do much about sea temperatures and ocean currents, but it can set sensible quotas on catches.
It probably makes sense that these quotas allow some cod fishing to continue, while reducing national fishing fleets and restricting the number of days that vessels are allowed at sea. Scientists can contribute to this process by acknowledging the uncertainties in their work. But it falls to fisheries managers and political leaders to persuade fishermen that quotas are fair and necessary.
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Fishing for excuses. Nature 431, 1023 (2004). https://doi.org/10.1038/4311023b