Fishers can heave a sigh of relief after a study found that ocean warming has no major impact on the number of fish.

The findings of the multinational study recently published in the journal Nature was based on the thousands of deeper fishery samples taken from 1993 to 2019.

Alexa Fredston, assistant professor in the department of ocean sciences at the University of California, Santa Cruz, and lead author of the study, said she was surprised by the findings.

The study found that heatwaves did not generally cause cold-water species to decline rapidly or     warm-water species to teem.

"We know that fish communities have responded to long-term warming of the oceans by moving toward the poles… so I anticipated similar findings — such as the fish community having more warm-affiliated species and fewer cold-affiliated species than usual — following marine heatwaves," Fredston said.

"Against the highly variable backdrop of ocean ecosystems, marine heatwaves have not driven biomass change or community turnover in fish communities that support many of the world's largest and most productive fisheries," she added.

The researchers analyzed data on 1,769 species in 82,000 catches by scientific trawlers in the north Atlantic and northeast Pacific, and on 248 deep-sea heatwaves "five days or more of extreme
higher-than-average warmth — recorded in the same period.

They noted a 22-percent loss of fish in the Gulf of Alaska after a marine heatwave in 2014 to 2016, and a gain of 70 percent in the northeastern United States after another heatwave in 2012.

Such cases, however, "were the exception, not the rule," the study said.

WITH AFP