Marine Environment: The Underestimated Overfishing | nd-aktuell.de

For hundreds of millions of people, fishing in the oceans is an indispensable source of food or livelihood. To ensure this in the long term, sustainable fishing is needed. However, according to the UN Food and Agriculture Organization (FAO), 37.7 percent of the stocks are overfished: more fish are caught than can grow back through natural reproduction. The industry itself repeatedly says that this trend is declining thanks to the catch quotas.

Australian scientists expressed doubts about this representation in a study published in the journal “Science”. The team, led by Graham J. Edgar from the University of Tasmania, examined the stock biomass estimates and trends used to set catch quotas. Result: Especially in overfished stocks, the quantities are in many cases overestimated and a “phantom recovery” is assumed, even though the stock continues to shrink. “Taking into account the distortions subsequently discovered, 85 percent more populations than currently recognized probably collapsed below 10 percent of the maximum historical biomass,” the researchers write.

The authors of the study compared the reported stock sizes with estimates from updated “hindcast” models with almost 1,000 stock surveys for the same year, which are currently considered the best database. Accordingly, the population sizes are often set too high, which means that the degree of decimation has been underestimated. This bias was most pronounced near the so-called critical depletion thresholds – which is when the pressure to fish less is strongest. “The results underscore how systematic biases can lead to management recommendations that are not conservative enough to maintain productive fish populations,” write marine biologists Rainer Froese and Daniel Pauly in an assessment.

Froese, who works at the Helmholtz Center for Ocean Research Kiel, also attributes this to the fact that it corresponds to the short-term wishes of those involved and the managers. »The problem here is the developed countries with institutes for fisheries science. They have given politicians wrong advice for years and again and again and thus bear part of the responsibility for the numerous overfished and collapsed stocks, including in Europe.

Boris Worm also attributes the fact that the populations of many species are in a much worse condition than stated, especially in overfished stocks, to economic interests: “These systematic overestimates do not occur in sustainably fished stocks – probably because fishing is going well and there is no reason There is a tendency to gloss over the results,” says the professor of marine biology from Dalhousie University in Canada. Overfishing is particularly a problem in the Mediterranean, where conflicts between riparian states prevent good fisheries management, as well as in West Africa and South Asia. However, particularly in regions where fishing is important for primary food supply and where the population density is not too high, simple but effective measures are often taken to protect stocks. Worm sees the study as a warning: “Many stocks that are still considered well managed – for example in Europe – could actually be worse off than expected.”

A warning can also be found in the study’s conclusion: “If we consider only the economic value, the inability to reverse the decline in fish stocks will ultimately have far-reaching negative effects on fisheries workers, ecosystems and their stability, and the capacity of the world to provide protein to a growing population.«