Fish provide a vital source of protein for over half the world’s population, with over 56 million people employed by or subsisting on fisheries. But climate change is beginning to disrupt the complex, interconnected systems that underpin this major source of food. A team of scientists at UC Santa Barbara’s Bren School of Environmental Science & Management has published an investigation of how warming waters may affect the productivity of fisheries. The results appear in the journal Science.
The study looked at historical abundance data for 124 species in 38 regions, which represents roughly one-third of the reported global catch. The researchers compared this data to records of ocean temperature and found that 8 percent of populations were significantly negatively impacted by warming, while 4 percent saw positive impacts. Overall, though, the losses outweigh the gains. They were surprised how strongly fish populations around the world have already been affected by warming,” and that, among the populations, the climate ‘losers’ outweigh the climate ‘winners.’ The region had the greatest influence on how fish responded to rising temperatures, according to the study
. Species in the same region tended to respond in similar ways. Fishes in the same families also showed similarities in how they responded to changes. The researchers reasoned that related species would have similar traits and lifecycles, giving them similar strengths and vulnerabilities. When examining how the availability of fish for food has changed from 1930 to 2010, the researchers saw the greatest losses in productivity in the Sea of Japan, North Sea, Iberian Coastal, Kuroshio Current and Celtic-Biscay Shelf ecoregions. On the other hand, the greatest gains occurred in the Labrador-Newfoundland region, Baltic Sea, Indian Ocean, and the Northeastern United States.
Although the changes in fisheries productivity have so far been small, there are vast regional discrepancies. For instance, East Asia has seen some of the largest warming-driven declines, with 15 to 35 percent reductions in fisheries productivity. Preventing overfishing will be a critical part of addressing the threat that climate change poses to the world’s fisheries. Ocean warming is just one of many processes affecting marine life and the industries that rely on it. Ocean acidification, falling oxygen levels, and habitat loss will also impact marine life. More research is necessary to fully understand how climate change will affect fish populations and the livelihoods of people that depend on them.
