By Richard Black
Environment correspondent, BBC News website
Fishermen would make even more money than previously thought if they let depleted stocks rebuild, according to research from Australia and the US.
Tuna fisheries would benefit in the long-run from catch restrictions
When fish are more plentiful it becomes easier and cheaper to catch them.
Now researchers have shown how bigger stocks would bring bigger profits for those in the industry.
Writing in the journal Science, they report that Australia is to start managing some of its fisheries this way from the beginning of next year.
The publication comes a couple of weeks before European fisheries ministers meet to decide 2008 quotas for many species, including the severely depleted cod.
"This is what some people may have suspected before, but we're the first to actually show the result," said research leader Quentin Grafton from the Australian National University (ANU) in Canberra.
"As soon as you start saying 'we're going to reduce the harvest', fishermen say 'you're going to make us worse off'; but we're saying 'if you reduce the harvest now, you'll actually be better off'."
Less is more
Traditional fisheries management centres around a concept known as Maximum Sustainable Yield (MSY) - the highest catches that can be taken year after year without running stocks down.
Many fisheries authorities that claim to aim for MSY are failing to achieve their target. The UN calculates that 75% of commercial fisheries globally are exploited either up to or beyond their sustainable limits.
While MSY management might yield the biggest catches, Professor Grafton's team calculated that fishermen would earn more if they kept stocks at a higher level, which they have named Maximum Economic Yield (MEY).
This is because as stocks fall, it becomes progressively more expensive to catch what is left. Keeping stocks higher and catching less might lower a fisherman's income, but it would lower costs even more.
The size of the extra profit, and the extra amount of stocks conserved, depends on the species, with the biggest effect noted in long-lived, slowly-reproducing organisms.
"So we looked at the orange roughy fishery off south-eastern Australia - that's a very long-lived species that can go up to 150 years," said Professor Grafton.
"We calculate that we should be conserving about 65% of the virgin biomass whereas at the moment we're down to about 30%.
"With a faster-growing species such as the [Australian] northern prawn fishery, you're at the other end of the spectrum."
With advice from scientists at ANU, the Australian federal government is to introduce MEY-based management for 26 species from the beginning of 2008, Professor Grafton said.
European fisheries managers theoretically aim for traditional measures of sustainability, though the quotas recommended annually by scientists are routinely inflated in the European Commission's proposals, and then inflated again when national ministers make the final decision just before Christmas.
A spokeswoman for Britain's environment ministry (Defra) said that although they acknowledged optimal stock sizes could be larger than indicated by MSY calculations, "The UK is committed to the Johannesburg agreement of bringing stocks to MSY levels by 2015, and this will still ensure a greater long-term security for stocks and their fisheries."
Martin Pastoors, chair of the Advisory Committee on Fishery Management within the International Council for the Exploration of the Sea (Ices), which provides the EU's scientific advice on fisheries, commented: "The simple logic of lower costs at bigger stock size seems plausible, and therefore higher profits at MEY above MSY.
But, he cautioned: "Low effort and high revenues mean that a small group of people could become very rich."
Overcapacity in the fishing industry, in Europe and elsewhere, means that many fishermen are competing harder for a smaller share of shrinking stocks; profit now, rather than when stocks have rebuilt later, is the imperative.
Quentin Grafton's team believes the new findings could enable fishermen, with support from their governments, to take out loans secured against future profits, enabling a temporary suspension of fishing on fragile stocks.
"Fishers individually wouldn't be able to borrow from banks, but with governmments they could - this could finance a transitional fund," he said.
This idea is being looked at in relation to tuna fisheries of the eastern Pacific, another area where high catches have brought some stocks to the brink of commercial extinction.