Official estimates substantially underestimate global fisheries catch, according to a new study published this week in Nature Communications.

Researchers have found that between 1950 and 2010, the “true” global fisheries catch — or the amount of fish taken from the world’s oceans — was likely more than 50 percent higher than what member countries voluntarily reported to the Food and Agriculture Organization (FAO) of the United Nations. Moreover, since mid-1990s, fisheries catch has been declining more sharply than what FAO’s data seems to suggest.

This decline is not due to countries fishing less, but because they are overfishing and exhausting fisheries stocks rapidly, researchers from the University of British Columbia in Canada found.

Currently, member countries mostly collect — and report – fisheries catch data of industrial or large-scale fisheries. A large part of fisheries catch data however, goes unreported, according to the study.

For example, estimates of catch from small-scale or artisanal, subsistence, and recreational fisheries, discarded bycatch, and illegally caught fish are generally not reported to the FAO, researchers say. Consequently, FAO’s official statistics underestimate the actual global fisheries catch. In fact, according to the study, FAO’s official data underestimates global fish catch by around 32 million metric tons every year.

“The FAO doesn’t have the mandate to correct the data that they get,” lead author Daniel Pauly said in a teleconference. “Countries have the bad habit of reporting only what they see.”

When countries report “no data” for certain fisheries, FAO records them as zero, Pauly said. And the result is a systematic underestimation of the fisheries catch, which can be very high, “up to 20 to 30 percent in developed countries, and 200 to 300 percent especially in small island states.”

To find out the magnitude of this underestimation, Pauly and Dirk Zeller of the University of British Columbia’s Sea Around Us research initiative, supported by The Pew Charitable Trusts, and Vulcan Inc., together with an international network of 400 colleagues, reconstructed and estimated historic catches of more than 200 countries between 1950 and 2010.

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They scanned through a broad range of direct and indirect sources including academic literature, industrial fishing statistics, local fisheries experts, fisheries law enforcement, human population, and other records such as documentation of fish catch by tourists, and compared their reconstructed estimates with those released by the FAO.

According to FAO data, starting in 1950, global fisheries catch increased steadily to 86 million metric tons in 1996, and then remained relatively stable or declined only slightly, by nearly 0.40 million metric tons per year. In 2010, fisheries catch fell to 77 million metric tons, according to the FAO.

In contrast, Pauly and Zeller’s independent estimates show that the catch peaked at 130 million metric tons in 1996, and then declined more strongly, by 1.2 million metric tons annually since then, to 109 million metric tons in 2010.

“These new estimates provide countries with more accurate assessments of catch levels than we have ever had, along with a far more nuanced portrait of the amount of fish that are being removed from the world’s oceans each year” Joshua S. Reichert, executive vice president and head of environment initiatives for Pew, said in a statement.

At the global scale, the researchers found that while industrial fisheries catch declined since mid-1990s, artisanal, subsistence and recreational catches have continued to increase.

However, some researchers, including the FAO, have questioned the study’s estimation methods. But Pauly said that his team is quite confident of the results. “This is not based on a few studies here and there and then extrapolation,” he said. “It is the result of 200 studies that were conducted over a decade by a network of 400 people in all countries of the world.”

Pauly and Zeller write that their reconstructed catch data could contribute to formulating better policies for governing the world’s marine fisheries. The first step in this would be to “recognize the likely magnitude of fisheries not properly captured in the official national collection systems.”

“This recognition will hopefully contribute to improvements in national data collection systems, an aspiration that we share with FAO,” they add. “It is hoped that this type of data [from recreational fisheries], and other missing data (for example, subsistence catches), will be included in future national data reports to FAO, as is the case for some other countries such as Finland.”

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Article published by Shreya Dasgupta. Source: Mongabay