The condition of fish populations in the world’s oceans is more dire than previously understood. Although overfishing has traditionally been attributed to fisheries policies that impose catch limits exceeding scientific guidelines, new research indicates that those scientific guidelines were often overly optimistic. Consequently, a significantly larger number of global fish stocks are either overexploited or have experienced collapse than previously recognized.
The health of fish populations in the oceans is worse than we had thought. Overfishing has often been blamed on policies within fisheries that set catch limits above what science recommends. A recent investigation by four Australian research institutions suggests that even these scientific guidelines were too optimistic. The outcome? There are many more global fish stocks that are either overfished or have entirely collapsed than we realized. Dr. Rainer Froese from the GEOMAR Helmholtz Centre for Ocean Research Kiel and Dr. Daniel Pauly from the University of British Columbia have shared their evaluations regarding the study. Their Perspective Paper, published today in the journal Science alongside the study, urges for simpler yet more precise models and advises a more cautious approach to stock evaluations when uncertainty arises.
A significant number of fish stocks globally face threats from overfishing or have already reached a state of collapse. A primary factor behind this alarming trend is that decision-makers have frequently disregarded catch limits set by scientists, which were meant to serve as strict protective measures for these populations. It has now become apparent that even the scientific recommendations were often too generous.
In the European Union (EU), fisheries management largely relies on permissible catch limits called quotas, determined by the European Council of Agriculture Ministers based on scientific advice and recommendations from the European Commission. A new study conducted by Australian researchers (Edgar et al.) indicates that the scientific advice has been suggesting catch limits that are excessively high.
The journal Science, which published the study today, consulted two of the leading fisheries experts globally, Dr. Rainer Froese from the GEOMAR Helmholtz Centre for Ocean Research Kiel and Dr. Daniel Pauly from the University of British Columbia, to interpret the results. In their Perspective Paper, they advocate for the development of simpler and more realistic models grounded in ecological principles, along with a demand for more cautious assessments and management strategies when uncertainties are present.
For their research, Edgar et al. looked at data from 230 fish stocks worldwide, concluding that stock evaluations have frequently been too optimistic. They inflated estimates of fish populations and the rates at which those stocks could recover. This issue is particularly severe for populations that have already dwindled due to overfishing. The inflated estimates resulted in “phantom recoveries,” where stocks were claimed to have recovered while they were actually still declining. “This led to insufficient reductions in catch limits during critical times,” explains Dr. Rainer Froese. “Regrettably, this issue persists as known overestimates of stock sizes in recent years continue to be overlooked in current assessments.”
The findings from Edgar et al. highlight that nearly one-third of stocks labeled by the Food and Agriculture Organization (FAO) as “maximally sustainably fished” have actually crossed into the “overfished” category. Additionally, the number of collapsing stocks (those with less than ten percent of their initial biomass) within the overfished category could be 85 percent more than previously estimated.
So, what leads to these inaccuracies in stock assessments? Standard evaluation methods can incorporate over 40 different parameters, such as fish life cycles, catch statistics, and fishing effort. The complexity arising from this multitude of parameters can make assessments cumbersome, as noted by Froese and Pauly. The results are only reproducible by a select group of experts who have access to the original models, data, and configurations. Many inputs also remain unknown or are challenging to estimate, prompting modelers to apply less reliable values that have worked in the past. Froese points out, “These practices can distort results to align with the modelers’ expectations.”
Therefore, the authors call for a reassessment of current stock assessment models. They advocate for the creation of simplified, more realistic models grounded in ecological principles. They also emphasize the importance of applying the precautionary principle: when uncertainty exists, conservative estimates should be favored to safeguard fish stocks. “Ultimately, sustainable fishing is straightforward,” states Dr. Rainer Froese. “You should remove less fish biomass than what is regenerated.” Fish populations need to be allowed to reproduce before they are harvested, environmentally sustainable fishing gear should be utilized, and protected areas must be established. It’s crucial to maintain essential food chain functions by decreasing catches of forage fish like anchovies, sardines, krill, and herring—these are the foundations of ecosystem-based sustainable fishing. Froese concludes, “Out of these five essential principles, four can be applied even without knowing the precise sizes of the stocks.”
