Netting better data on global fish stocks

Jop de Vrieze in Science Now: Overfishing is a major global concern—but that concern tends to focus on just a few well-studied fish, such as salmon and herring. Current assessments cover only 20% of the world's fish stocks, so the true state of most of the world's fish populations is still murky. Now, a new method based on catch data and fish characteristics suggests that those unstudied stocks are declining—but also that better management of global fisheries could boost the status of many of those stocks and could also increase the global sustainable fish harvest by as much as 40%.

When fisheries are managed well, they can be a source of large amounts of food and economic value without irreversibly disrupting ecosystems and depleting fish numbers. But industry lobbying, corruption, fears that reducing fishing capacity will lead to unemployment, and other economic and political obstacles have made sustainable fisheries management difficult in practice.

Meanwhile, even as they discuss measures for sustainable management, conservation scientists and fisheries scientists are locked in a disagreement about whether global fish stocks are in crisis. In 2006, marine ecologist Boris Worm of Dalhousie University in Halifax, Canada, and colleagues published a paper in Science that projected that if current practices remain unchanged, all fish stocks would collapse by 2048. This projection received heavy criticism from fisheries scientists, who said that the number of recovering stocks actually shows an overall improvement.

Fish like salmon and herring are, in general, strictly managed. Their condition is assessed through sampling to determine stock size, as well as through catch data and population models that examine factors such as the fish's growth, how often they reach maturity, and how quickly they reproduce.

But no such assessment takes place for 80% of current fish stocks, which include more than 7000 populations. This neglect applies to many uncommon fish species, as well as to some stocks of well-known species such as cod and tuna....

Konstantine Volanakis, "The Fishnet"