Investigation Reveals Global Fisheries Are Worse Off — and Many Have Already Collapsed

When fish are taken from our oceans faster than they can reproduce, their population numbers decline. This over-fishing upsets marine ecosystems. It’s also bad for human populations that rely on fish for protein in their diets.

Our investigation tested how accurate estimates of fish stocks actually are. It involved examining data from 230 of the world’s largest fisheries, spanning 128 fish species.

To manage fishing areas sustainably, we need accurate data on how many fish exist and how abundant they will be in future. Fisheries scientists use complex mathematical models to determine this.

But an investigation by my colleagues and I, published today in the journal Science, casts serious doubt on the accuracy of these models.

We studied 230 fisheries around the world. We found populations of many overfished species are in far worse condition than has been reported, and the sustainability of fisheries was overstated. Urgent action is needed to ensure our oceans are not fished below their capacity to recover.

A sustainable fishing operation would ensure the numbers of fish caught does not outstrip the capacity of a fish population to reproduce. In cases where an area has been overfished, stocks should be given time to rebuild…

Among over-fished stocks, we estimated the number of collapsed stocks was likely 85% larger than currently recognized.

So what did we find? The earlier stock assessments were often too optimistic about the number of fish in the ocean.

For sustainably fished stocks, the earlier estimates were generally accurate. But for stocks that were overfished, most earlier data turned out to be substantially overestimated. In many cases, fish stocks were regarded at the time to be recovering when they were in fact declining.

Among over-fished stocks, we estimated the number of collapsed stocks was likely 85% larger than currently recognized.

Our research shows the global problem of overfishing is far worse than currently recognized. So what should be done?

Clearly, scientists should try to improve the accuracy of models used to assess fish stocks. And management of fisheries should be far more cautious, to protect fish stocks around the world. This is vital for sustainable fisheries, healthy oceans, and our own food security