Counting all the fish in the sea may be even trickier than scientists thought
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On average, the fish stocks across the world that the study examined were at healthy levels.
PHOTO ILLUSTRATION: UNSPLASH
NEW YORK - 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, including 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.
But as fishery scientists often say, counting fish is a lot like counting trees, except that they move and you can’t see them.
In fact, many assessments of the health global fisheries may be too optimistic, according to a new study published Aug 22 in the journal Science.
The researchers analysed data from 230 of the most important fisheries in the world from 1980 to 2018.
On average, the study found, assessments overestimated fish stocks by 11.5 per cent. The findings, the researchers said, highlight that governments need to take more precautions to protect fish populations.
On average, the fish stocks across the world that the study examined were at healthy levels, though some overfished populations, like the blue king crab, are still struggling to recover.
Optimism about the state of fisheries was most pronounced in ecosystems that the study’s researchers considered overfished.
According to the study, assessments of these struggling fisheries tended to project recoveries of fish populations that never fully materialised.
“We’ve worked across all of these stocks and see this signal that tells us we’re basically overestimating, on average, how much is out there,” said Dr Amanda Bates, a marine ecology professor at the University of Victoria, in British Columbia, and one of the authors of the study. “And we’re making management decisions based on that.”
The study’s findings divided scientists. Underlying the disagreement was a recognition that estimating the number of fish in the ocean is incredibly hard.
The pressure to get it right comes from many directions.
“Fishery management is always a balance between conservation, food security, fishing jobs and economics,” Dr Steven Cadrin, a marine scientist at the University of Massachusetts Dartmouth, said. NYTIMES
