Many fish migrate or die when the water gets too hot, but millions could be saved if the world meets the global warming targets in the 2015 Paris accord, a recent study said.
Fish are an important part of the food chain and a global industry worth $148 billion in exports each year worldwide.
Findings in the US journal Science on Thursday compare the scenarios of 1.5 Celsius of warming (2.7 F) above the pre-industrial days, as set forth in the Paris deal, to 3.5 C by century's end, or the path the planet is currently on.
If global warming continues unchecked, and the 3.5 C scenario comes to pass, the depletion of fish populations would deprive the industry of six million tons of catch each year, the study found.
Since fisheries near the equator would be most negatively affected if the Paris targets are not met, the people who rely on fish for their livelihoods there are also more likely to suffer than their counterparts further north.
The maximum catch potential could drop 47 percent in the Indo-Pacific region, which includes the Bay of Bengal, Gulf of Thailand, South China Sea, and Sulu-Celebes Sea, the study said.
"The benefits for vulnerable tropical areas is a strong reason why 1.5 C is an important target to meet," said lead author William Cheung, associate professor at the University of British Columbia's Institute for the Oceans and Fisheries.
"The seafood supply chain is now highly globalized. Everyone would benefit from meeting the Paris Agreement."
The study analyzed data from 19 Earth system models, comparing outcomes for nearly 900 marine fish under a scenario of continued high greenhouse gas emissions to stronger fossil fuel cutbacks. Under either scenario, the amount of fish will decline.
A warming increase of 3.5 C "will decrease the maximum catch potential on a global level by eight percent," the study said. Temperature increases of 1.5 C "will decrease maximum catch potential by 2.5 percent."
Researchers said the findings should convince countries - including the United States under President-elect Donald Trump, who has threatened to abandon the deal - of the importance of increasing their commitment to reducing greenhouse gas emissions.