August 23, 2024 — Counting the number of fish in the ocean may well be one of science’s toughest jobs. It also produces a crucial tool governments use to protect marine ecosystems that feed millions of people across the world.

Fish stock assessments work a lot like climate models. Scientists gather a wide range of data from fish catches, like age and weight, and track environmental conditions, like the temperature of the sea, and use mathematical models to estimate the health of fish populations. The analysis is then used to make recommendations to governments.

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“A lot of the things they say you need to do are already in place,” said Ray Hilborn, a professor of fishery science at the University of Washington. Many fishery managers, he explained, already look back at historical trends to correct for a possible tendency to over or undercount fish populations.

Steven Cadrin, a marine scientist at the University of Massachusetts Dartmouth, who has worked on fish stock assessments for decades, said the study’s findings are “invalid,” partly because the researchers used the most recent stock assessments as a benchmark for accuracy. More recent tallies of fish populations may be just as prone to error, he said.

The fisheries included in the study have some limitations. The study’s researchers examined fish assessments with ample data, which are largely done by some of the wealthiest countries in the world, such as the United States, Canada and Australia.

Still, some of the most troubled fisheries, in countries like India and Indonesia, don’t do thorough fish stock assessments, Dr. Hilborn said.

“The global fisheries problem,” he said, “is that about half of the world’s fish stocks are simply not assessed.”

Read the full article at The New York Times