Large Fish in the Ocean

Large fish in the ocean like tunas and billfishes are highly sought-after and compose some of the most valuable fisheries in the world. The Pacific bluefin tuna population has famously been overfished to less than 10% of its original population, but rumors of other large fish declines in the ocean have been greatly exaggerated.

In 2003, a paper used catch-per-hook data from Japanese longline fisheries to claim that, by 1980, 90% of large fish in the ocean had disappeared. This was a ridiculous assertion for two main reasons:

First, catch-per-hook data can be a proxy for abundance in some situations, but if other, better data exist that gives a more accurate estimate, that is always preferred. Better data exists to estimate abundance, so catch-per-hook was a poor, inaccurate choice. The best available science shows that most tuna stocks remain above the target levels that will produce maximum sustainable yield.

Second, the catch of tuna and billfish increased 2.5 fold from 1980 to 2006. So how could the stocks have been depleted by 1980 and the catch still managed to increase so much?

The figure below from a 2006 paper in Science shows the history of catches of major tuna stocks.

Further, a 2011 paper used stock assessment data to estimate that tuna stocks around the world were at about 50% of the abundance they had been before industrial fishing began.

By 1980, the tuna stocks were at 80% of their abundance before industrial fishing, not the 10% argued in the 2003 paper.

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Learn more about sustainable seafood below.