Fish Stocks Fall Due To Oceans Warming

Fish catches have declined markedly and are likely to fall further, a study has found, with warming oceans to blame. Around the world, fish populations have fallen over the past 80 years, although some species have shown greater resilience than others. Overall, catches of commercially important fish have fallen by just over 4%, but in some regions catches have plunged by about a third since early in the last century. The findings come from a study that has used “hindcasting” methods to reconstruct the effects of global warming, overfishing and other impacts on fisheries over the 80-year period from 1930 to 2010.

The researchers, whose work is published in the journal Science, examined fish populations in 38 regions, studying 235 fish populations made up of 124 species, which represented about a third of the global fishing catch over the period studied. Changes in temperature were found to have an important effect, along with other problems such as overfishing and ocean acidification. They used data on catch sizes, fish populations and temperatures to build a picture of how fishing, sea temperature increases and other factors had an effect on fish populations over the period studied.

Christopher Free, of the University of California, Santa Barbara, who led the research, said the overall picture was one of losses to fish populations, even though some species, such as black sea bass in the Atlantic, showed gains as sea temperatures rose. Olaf Jensen, associate professor at Rutgers University in New Jersey and a co-author, warned that species that had benefited from warming were “likely to start declining as temperatures continue to rise.” The greatest losses found in the study were of fish in the North Sea near the UK, the sea of Japan, around the Iberian coast and the Celtic-Biscay shelf. There were gains among fish populations in the Labrador-Newfoundland region, the Baltic Sea, the Indian Ocean and the north-east US shelf. Historical data on many tropical regions is limited, leaving the researchers unable to form a clear picture in such areas.

Credit: Fiona Harvey for The Guardian, 28 February 2019.