Many developing nations with coastlines depend on their exclusive fishing grounds for food security. They are also in an increasingly difficult situation: warming oceans are sending many of their fish to cooler latitudes. Some researchers believe that smart management of the high seas may be instrumental in mitigating the effects of rising ocean temperatures and increasing food security in the tropics.

In a recent study, a group of researchers from the University of British Columbia has found that closing the high seas to fishing would increase fish stocks by as much as 10 percent by 2050 in the oceans’ so-called Exclusive Economic Zones, which are fishing grounds near a nation’s coast that are theirs—and only theirs—to fish.

Because 42 percent of fish stocks straddle the high seas and EEZs, a reduction of takes from the high seas is projected to increase the amount of fish available closer to shore. Now researchers have calculated by just how much.

In a paper published recently in the journal Fish and Fisheries, researchers looked at 30 fish stocks that straddle the high seas and EEZs, which includes the waters within no more than 200 nautical miles of a nation’s coastline. They used computer models to calculate where these fish would be found under different combinations of two climate change scenarios (high and intermediate emissions) and three high seas management scenarios: status quo, high seas closure, and cooperative management of the high seas. They calculated the differences in catches and species abundance from the baseline year of 2000 to 2050.

They found that under the cooperative management regime, in which the high seas were well governed, fish stocks in the EEZs would increase by 4.7 or 6.3 percent by 2050 as compared to 2000, depending on the climate scenario. The high seas catches would increase by 163 or 171 percent. If the high seas were closed altogether, catches in the EEZs would increase by 8.5 to 10.3 percent, while high seas catches would decrease to zero.

While the good governance scenario increases overall global catches by approximately 26 to 29 percent, the high seas closure decreases them by 3.4 to 5.6 percent, depending on the climate scenario. Doing nothing would decrease catches in both ocean zones.

When it comes to the abundance of species, however, the high seas closure greatly outperforms the cooperative management approach. In a high emissions scenario, high seas closure produces a 27 percent increase in species abundance in the EEZs as compared to around 10 percent increase under cooperative management.

According to the lead author William Cheung, a total closure might be logistically easier to enforce than good management. But good management might be easier to achieve politically.

“I think what it should come down to is a portfolio of management options, because there are pros and cons to each approach,” he says.

He says either of these options would provide for a more equitable distribution of the seas’ resources, considering that relatively few nations fish the high seas, and that only ten of these took 62 percent of all high seas landings in 2010. But whether developing nations would actually benefit from changes on the high seas depends on how well they manage their own fishing grounds and the new influx of straddling stocks that would come migrating their way. —Catherine Elton | 16 September 2016

Source: Cheung, W. et al, Transform high seas management to build climate resilience in marine seafood supply. Fish and Fisheries. 2016.

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