Global warming looks set to be a bigger problem for the world’s fish than scientists initially thought: a new study shows that fish are more vulnerable to rising water temperatures when they are laying eggs or in the embryo stage.
Washington (AP) — The world’s oceans, rivers and lakes will be too hot for about 40 percent of the world’s fish that are spawning or in embryo by the end of the century, according to a study published Thursday in the journal Science. This means they may become extinct or be forced to change the way and place they live and breed.
Biologists had previously studied only adult fish. Under similar warming estimates, about 2 to 3 percent of adult fish will be in areas that are too warm by 2100. So the use of the new method reveals a previously unknown question about the future of fish, scientists say.
In the worst-case scenario, the proportion of fish in trouble would jump to 60%.
Hans-otto Portner, a Marine biologist at the Alfred Wegener Institute in Germany and co-author of the study, said these vulnerable periods in an ichthyoid’s life could be a “bottleneck” for the future health of the fish. Last year, an ocean heat wave known as the “warm Water Mass” killed large Numbers of migrating salmon in Alaskan rivers. The ocean heat wave also destroyed cod eggs, showing what a warming future might look like, said lead author Fleming Dalke, a Marine biologist at the Alfred Wegener Institute.
“Spawning fish and fish embryos are the most sensitive to rising water temperatures, which means fish populations will not be able to reproduce themselves,” said Marin Pinsky, an ecologist at Rutgers University. If the fish don’t breed and have no offspring, then we won’t have fish and fisheries and we won’t have fish on our plates.” Pinsky was not involved in the study but praised it.
In their study of 694 fish species, Dalke and Portner found that some of the fish likely to be most affected by rising water temperatures include Alaskan cod and well-known species such as red salmon, brown trout, skipjack, pike and swordfish.
“The more we let the temperature change… The more we lose the natural basis of human life, including food from the sea.”
When the water gets too warm for spawning, the fish can still move to cooler waters or choose another time to spawn, but that’s not easy, Dalke said.