Research reveals: Fishing activities are excessively high
Many fish populations globally are under threat or have declined significantly. Researchers from a team led by Graham Edgar from the University of Tasmania (Australia) have found that this is not just due to overfishing beyond scientific limits, but also because the original catch limits were too high in the first place. A study published in the journal "Science" suggests that these recommendations were overly optimistic, leading to unemployment levels that were not low enough to allow for population recovery.
Fishing models are used as a basis for regulating global and regional fisheries and are regarded as a key tool against overfishing. Until now, it was believed that the primary cause of overfishing was the setting of catch limits higher than those recommended by the models.
Excessive Overestimations
The team analyzed data from 230 fish stocks worldwide and compared it with those from regulatory models. The findings revealed significant overestimations of the number of fish in a particular species and the speed at which a population could recover. This was more pronounced in overfished populations.
According to the analysis, even populations considered to be recovered continued to shrink in reality, resulting in catch levels that were not reduced enough despite the urgent need for it.
Overfished Instead of Sustainably Fished
The study found that almost a third of the stocks classified by the FAO as "maximally sustainably fished" are actually overfished. Fishing is deemed sustainable if no more fish are caught than can replenish.
Moreover, more populations have collapsed than previously thought: 85% more populations have collapsed, shrinking to less than 10% of their historical maximum.
According to Froese and Pauly, the models use up to 40 parameters, including characteristics of the species' life history, catch details, and the required fishing effort. This complexity makes the estimates unnecessarily complex and sometimes relies on questionable values for some parameters, the authors argue.
Simpler Models Needed
"Why the sometimes bogus predictions of the official models were accepted and continue to be accepted is the big question," said Froese. He noted that fisheries science have been misguiding policy for years and bears some responsibility for the overfished and collapsed stocks, even in Europe.
Overfishing is particularly a problem in the Mediterranean, West Africa, and Southeast Asia, explained Boris Worm from Dalhousie University (Canada), who was not involved in the study. He warned that "several stocks still considered well-managed, such as in Europe, might actually be in worse shape than thought."
Baltic Sea Example: Cod
The phenomenon can be seen with the cod in the western Baltic Sea, explained Christian Möllmann from the University of Hamburg. "The often overly optimistic estimates of biomass have, in my opinion, also contributed to the overfishing of this stock."
An update of the assessment methods is needed - towards simpler, more realistic models, conclude Froese and Pauly. Moreover, the precautionary principle should be applied more strongly - conservative estimates should be used in case of uncertainties.
Möllmann, however, saw the quality of the models as less important. "More important, in my opinion, is the willingness of the fishing industry not to exploit every fish from the sea." The willingness and understanding to fish sustainably and responsibly is often lacking.
This is evident in the Baltic Sea, where all once important cod and herring stocks, despite years of warnings from scientists and environmental organizations, have been overfished to the point that recovery is largely uncertain or even unlikely.
The findings from the study suggest that overfishing is not solely due to catch limits exceeding model recommendations, but also because the initial catch limits were overly optimistic, leading to insufficient population recovery. Despite some populations being classified as maximally sustainably fished, the analysis reveals that almost a third of these stocks are actually overfished.
