Build up fish stocks now for big money later: study

By Deborah Zabarenko, Environment Correspondent

WASHINGTON (Reuters) - Commercial fishers should cut back on their catch and allow fish stocks to grow above the levels most governments currently advise if they want to boost long-term profits, economists reported on Thursday.

Such a strategy would sustain fish populations and save fuel while opening the way to big profits in the future, the researchers reported in the journal Science.

And the more depleted a fishery has become, the better the results when stocks are built up to what the researchers call the biomass maximum economic yield. That might be 10 to 20 percent over what fisheries managers now aim for, which is the level at which fish populations can be sustained.

Co-author Quentin Grafton of the Australian National University condensed the results to five words: bigger stocks mean bigger bucks.

At the same time, the authors suggest that when profits from fishing are maximized, it's more likely that fish populations will be maintained, and fishers will use less fuel seeking out fish, since they won't be that scarce.

"In many fisheries of the world, profitability is close to zero and in some cases it's even negative," said Quentin Grafton of the Australian National University in a telephone interview. "So what we're suggesting here is we can ... turn around the current state of affairs to make them profitable and also increase the number of fish in the sea."

To illustrate how this could work, Grafton gave an extreme example:

Imagine there is only one tuna left in the entire Pacific Ocean, a body of water that covers about one-third of the Earth's surface. The cost of catching that tuna would be hundreds of millions of dollars, because finding it would be nearly impossible.

But if there were hundreds of millions of tuna in the Pacific, the cost of catching them would be much lower, because fishers wouldn't have to travel as far or look as hard. With this lower cost, profits would rise.

This system would counter a persistent cause of over-fishing: industry's opposition to lower catches.

Grafton and his co-authors tested their idea by looking at revenue and profit curves for four different fish: big eye tuna and yellow fin tuna in the western and central Pacific, and northern tiger prawn and orange roughy in Australia.

In all four cases, they found the "stock effect" -- that is, when fish are more plentiful, they're cheaper to harvest. This effect had not been taken into account in previous calculations of the best levels for fish stocks.

To build up the fish populations to the higher level, governments would have to persuade fishers to limit but not eliminate their catch, Grafton said. This could be done by subsidizing fishers during the lean period and taxing them after fish stocks are rebuilt.

To keep fish stocks profitably high, enforceable catch limits would be essential, he said.