A recently published study has reiterated the long-discussed issue of climate change causing changes in distribution of marine species – which is putting strain on managing shared fishing stocks.
The study, published in Science Advances, examined 347 different “straddling” fish stocks across 67 species that are present in multiple exclusive economic zones (EEZs) and the high seas. Those stocks are often managed via cooperation between multiple coastal states or between multiple regional fishery management organizations (RFMOs).
“Previous studies have identified thousands of transboundary stocks with an estimated total catch of 48 million metric tons valued at [USD] 77 billion [EUR 66.1 billion] in 2014,” the study states.
According to the findings, regardless of the climate change scenario model the study applied to the stocks, at least 37 percent are projected to shift between EEZs and the high seas by 2030, and 54 percent will shift by 2050. Those stocks will shift in multiple ways, including from EEZs to the high seas and in the high seas across multiple RFMOs.
“Climate change is adding another layer of complexity to the study, governance, and management of straddling stocks,” the study states. “Climate change is driving shifts in marine species distributions, with many moving toward higher latitudes, deeper waters, or along local environmental gradients, such as localized currents and upwelling systems. These distribution shifts alter the sharing of fish stocks across jurisdictional and management boundaries.”
The shifts in distribution were not necessarily all the same, but the study found that stocks from “nearly all commercial groups” are projected to experience significant shifts by 2050. Those shifts differ, with some moving toward EEZs, while others will shift away from EEZs and toward the high seas.
“Notably, only the salmon, smelts, and similar species group are projected to show no significant shift in distribution,” the study said.
The study added that those shifts in stocks will cause more challenges for fisheries managers trying to maintain sustainable fishing, which will compound on existing issues for shared stocks.
“The management of shared stocks is more challenging than that of species restricted to a single EEZ. It depends on the proper identification of the distribution boundary, the importance of the stocks to resource users, and collaboration among resource users and managers,” the study said. “Thus, fish stocks are more likely to be overexploited when they are shared than when confined to a single EEZ.”
Issues with shared stocks are apparent in the management issues already facing commercially important fish stocks. One example is the ongoing management crisis facing the Northeast Atlantic pelagic fisheries.
Multiple species in the Northeast Atlantic – including mackerel, spring spawning herring, and blue whiting – have lost certifications and had their sustainability metrics downgraded as coastal states in the region fail to agree on a way to end overfishing of the stock.
According to the new study, climate change will add another level of complication to the challenge of quota negotiations, too, as fishing stocks move across management boundaries, leaving countries that depended on the stock with fewer fish to catch.
“By 2050, a substantially larger number of stocks are projected to shift, with the magnitude of change being particularly pronounced under a high-emission scenario,” the study said. “As a result, coastal nations and RFMOs urgently need to adapt their management and governance structures to account for and accommodate these shifts and their associated impacts to ensure sustainable and equitable resource management, incorporating dynamic stock assessments, adaptive management strategies, and enhanced international cooperation.”
