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 led by Christopher Free, a postdoctoral scholar 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.

“We were surprised how strongly fish populations around the world have already been affected by warming,” said Free, “and that, among the populations we studied, the climate ‘losers’ outweigh the climate ‘winners.'”

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.

Source: Warm seas scatter fish