Although in recent years more distinctions have been drawn between aquaculture and capture fisheries, these sectors are still inextricably linked in many ways, both biologically and economically. According to the FAO, over the past century aquaculture has grown to provide 57 percent of our planet’s aquatic animal production destined for human consumption. In contrast, the portion of marine fisheries stocks within biologically sustainable levels was 62.3 percent in 2021, down 2.3 percent from 2019. Clearly, there are innumerable species and markets for which aquaculture production is not a practical option, and the FAO emphasizes that urgent action is needed to accelerate conservation and rebuilding of fisheries stocks. However, as we all know, you can’t manage what you don’t (or can’t) count.
A recent research article in the journal science indicates that the stock assessment data available to fisheries managers are not necessarily accurate, and often unrealistically optimistic. Edgar et al. (2024) examined stock assessments for 230 fisheries across the globe. The stocks in question represented a best case scenario, if you will, since they were comparatively well-documented and managed. Most stock assessments allow the use of current information to estimate biomass in previous years (“hindcasting”), and the study compared original stock biomass estimates with those for the same point in time generated from subsequent, updated assessments done several or many years later. The authors attempted to identify systematic bias over time and how such bias might vary with the status of any given stock.
A total of 756 biomass values from older stock assessments were compared with estimates for the same year (“hindcast values”) derived from the most recent assessments for the same stocks. The further back in time, the more the older assessments overestimated biomass at that given point in time. Stocks considered as overfished generally exhibited large downward revisions in later assessments, with a consistent tendency of perceived recoveries that only dissipated over time. One important finding was that inaccurate historical data can often result in the perception that overfished stocks are in recovery and require less stringent regulatory control, which tends to perpetuate overfishing.
Edgar et al. identified sea surface temperature as one of seven potential contributors to bias in biomass estimates over time, as a result of unpredictable interactions and ecosystem alterations. Recent events have served to emphasize the potential for climate change impacts to render stock assessments virtually useless. Consider the human-induced collapse of the Bering Sea snow crab fishery. Although the consensus in 2018 recognized a sustained period of stock increases, catches decreased significantly for four years straight. Following a catastrophic stock assessment in 2021 the fishery was closed the following year. Litzow et al. (2024) developed an index to quantify the shift from arctic to boreal conditions in traditional snow crab fishing grounds over the time period in question. They tracked trends in ice cover, bottom temperature, primary production and the composition of phytoplankton, zooplankton and groundfish communities. Changes in prey availability, suitable habitat, predation pressure and disease prevalence were all demonstrated to track with the boreal index.
Illegal, unreported and unregulated (IUU) fishing also complicates efforts to assess and manage fish, crustacean and mollusk stocks through the globe. In a study published in 2020, Sumaila et al. used ecological and economic data to estimate the scope of illicit trade in marine fishes. They concluded that this trade involves between 8 and 14 million metric tons of unreported catches on an annual basis. Apart from detrimental impacts on fisheries stocks and ecosystems, the authors projected resulting annual losses of $26 to $50 billion to the world’s traditional, legitimate trade in marine finfish. The authors also emphasized the fact that IUU fishing is undermining the ability of many coastal countries to achieve United Nations’ Sustainable Development Goals.
What impacts wild fisheries often impacts aquaculture, and sometimes in unanticipated ways. We would be wise to stay abreast of the sector’s realities, uncertainties and challenges going forward, to identify both opportunities and threats.
— C. Greg Lutz, Editor-in-Chief