A new paper in the Proceedings of the National Academy of Science shows that there is a triple bottom line, that abundance, catch and profit can all be increased by reforming fisheries management in places where it has not been reformed. It provides the most comprehensive estimates of the status of global fisheries and shows that the large fish stocks of the world that provide 95% of global catch on average are at about the abundance that would produce long term maximum yield, and fishing pressure, on average is below traditional targets. Less than 20% of fish stocks appear to be overfished by U.S. standards.

Comment by Ray Hilborn, University of Washington, @hilbornr

The paper by Costello and others (including myself) Global fishery prospects under contrasting management regimes that appeared March 28 in PNAS, provides the most comprehensive assessment of the status and potential of global fisheries. Its key finding is that when stocks are overfished, most can recover within 10 years if the appropriate management measures are taken. This means that globally we could have more catch, more fish in the ocean and more profit. Most of the potential for this “triple bottom line” comes from Asia where fisheries are both large, and at present, mostly unmanaged. We must distinguish between fisheries that are reformed and those that are poorly regulated and remain in a race to fish.

Diving deeper into the estimated current status of fish stocks, we find it depends greatly on the size of the stock. Although the paper examined the status of 4,324 individual stocks, just 719 of them provide 96% of the catch. From the perspective of catch, profitability, and fish in the ocean, it is the 719 that are critical and feed us.

We find a very close relationship between the status of fish stocks and their size. One measure of stock status is their average size relative to their abundance that would produce long term maximum yield. Small stocks with potential yield of less than 1,000 T are at 76% of the level that would produce long term yield. The largest stocks (> 500,000 T potential yield) on the other hand, are at 1.34 times this target level. Essentially, small stocks are fished harder than large stocks.

Status of Global Fisheries

The large stocks with potential catch > 10,000 MT are, on average, above the biomass target and below the fishing mortality rate target – meaning they are generally in good shape. However, within each group there are stocks that are overfished (15-19%) and many that are fished harder than good management would dictate.

Why are big stocks in better shape than small stocks? One major reason is that governments, industry and NGOs devote more management effort to large stocks. A second possible reason is that the data available on small stocks are less reliable than for large stocks. We used the catch data provided to the Food and Agriculture organization of the United Nations by individual countries. FAO staff recommended not using stocks with less than 3,000 MT catch, which would eliminate a little over 3000 of the stocks in the analysis.

If we look at only U.S. fish stocks, the status is even better. Again large stocks are generally in better shape than small stocks, but abundance is higher, fishing pressure is lower, and the percent overfished lower. Again stocks with a potential yield of more than 10,000 tons constitute 96% of potential yield.

Of particular importance is the low fishing pressure for the larger stocks, so low that the U.S. as a country is giving up considerable potential yield by fishing so conservatively. This analysis suggests we could almost double U.S. harvest by fishing at a rate that would maximize long-term yield.

Status of U.S. Stocks

A significant limitation in the analysis is that we assume that all stocks are independent and each could be managed to produce its maximum benefits. Many of the problems with U.S. fisheries, and indeed fisheries around the world, occur in mixed stock fisheries. Most U.S. mixed stock fisheries are limited by weak stocks. For example, catch of haddock and redfish in New England is limited by cod and yellowtail flounder; the catch of many species on the West Coast is limited by yelloweye rockfish; catch of pollock and groundfish in Alaska is limited by bycatch of halibut and salmon. So long as the U.S. insists on trying to minimize the number of overfished stocks, we will have to keep exploitation rates on many species low.

Ray Hilborn is a Professor in the School of Aquatic and Fishery Sciences at the University of Washington. Find him on twitter here: @hilbornr