Managing fisheries to maximize profits got a bad name in the 1970s after an economist concluded that overexploitation, even to the point of causing a stock to go extinct, is a definite possibility when fishers are pitted against each other and are attempting to maximize profits.

The seminal 1973 article in Science was not a study of how fishers actually behave but was a mathematical exercise weighing the profit advantages and disadvantages of overexploitation.

A new way of looking at maximizing fishery profits, published this week in Science, comes to a different conclusion -- one that could lead fishers to buy into the idea of catching fewer fish than they are allowed under commonly used management guidelines.

That's because when fish are abundant enough, the cost to catch each one -- in terms of such things as fuel, vessel time and labor -- goes down, according to Ray Hilborn, University of Washington professor of aquatic and fishery sciences and a co-author on the paper.

In the four fisheries examined for the paper the researchers found that once the fish reached their target abundance it took 20 to 30 percent less "fishing effort" to harvest the same -- or slightly less -- catch than previously.

Lower costs mean higher profits.

To lower the costs one needs to have more fish -- or biomass -- than are available under, say, the traditional management goal of "maximum sustainable yield." Maximum sustainable yield aims for fishers to catch the maximum amount of biomass that is sustainable. It's widely used by many countries and management agencies, including the United States' National Oceanic and Atmospheric Administration.

Knowing higher profits await them could help fishers suffer through the pain of not fishing as much for a while to let stocks grow to levels above those of maximum sustainable yield, Hilborn says. Just how much a stock would need to regrow and how fast that could happen varies between fisheries, taking longer for instance for fish that reproduce slowly.

In practice, maximizing profits is only going to work where systems are in place that allocate catch to individuals or groups of fishers rather than where there is a race to fish in which one can increase one's total catch by fishing more or buying a bigger boat, Hilborn says.

"Appropriate incentives in the form of individual or community harvesting rights can provide security to current fishers that they will benefit from stock rebuilding," the authors write. Other authors on the paper are research director Quentin Grafton and Tom Kompas of the Crawford School of Economics and Government at the Australian National University.

The findings are contrary to the 1973 Science piece "The economics of over-exploitation," written by Colin Clark of the University of British Columbia. Clark wrote, ". . . in concentrating their attention on the problems of competitive overexploitation of fisheries, economists appear to have largely overlooked the fact that a corporate owner of property rights in a biological resource might actually prefer extermination to conservation, on the basis of maximization of profits. In this article I argue that overexploitation, perhaps even to the point of actual extinction, is a definite possibility under private management of renewable resources."

The new work makes better calculations of fishing effort and shows it would never be profitable to fish a stock to extinction. As fish become more scarce, "fishing profits become negative long before biomass is fully depleted," the new paper says. The four populations analyzed were the big-eye and yellow-eye tuna of western and central Pacific, and the northern tiger prawn and orange roughy of Australia.

The authors call this new approach a win-win for groups wanting to see depleted fish stocks rebuilt and fishers wanting to stay in business because conservation promotes both large fish stocks and higher profits.

"Revisiting the economics of overexploitation provides both a target and a framework to help overcome a key cause of overharvesting: fisher opposition to lower catches associated with stock rebuilding," the authors write.