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Friday, July 03, 2020 1:00 am

Warming water threat to future of fish species

Associated Press

Global warming looks like it will be a bigger problem for the world's fish species than scientists first thought: A new study shows that when fish are spawning or are embryos, they are more vulnerable to hotter water.

Based on end-of-century projections for human-caused climate change, the world's oceans, rivers and lakes will be too hot for about 40% of the world's fish species in the spawning or embryonic life stages, according to a study in Thursday's journal Science. That means they could go extinct or be forced to change how and where they live and reproduce.

Until now, biologists had studied only adult fish. For adult fish, around 2% to 3% of the species would be in the too-hot zone in the year 2100 with similar projected warming. So using this new approach reveals a previously unknown problem for the future of fish, scientists said. In a worst-case climate change scenario, which some scientists said is increasingly unlikely, the figure for species in trouble jumps to 60%.

These vulnerable times in the life of a fish make this a “bottleneck” in the future health of species, said study co-author Hans-Otto Portner, a marine biologist at the Alfred Wegener Institute in Germany.

A marine heatwave last year, known as a blob, caused large numbers of migrating salmon to die throughout Alaska's rivers. It also killed off cod eggs, showing what a warmer future might be like, said study lead author Flemming Dahlke, a marine biologist at the institute.

In studying 694 species, Dahlke and Portner found that some of the fish likely to be hardest hit by this phenomenon include Alaska pollock – the biggest U.S. fishery and the source of fast food fillets – and well-known species such as sockeye salmon, brown trout, bonito, barracuda and swordfish.

Also

Wolverine's status to be decided

BILLINGS, Mont. – U.S. wildlife officials have agreed to make a determination by the end of August whether climate change and other threats are pushing the rare wolverine closer to extinction in the mountains of the West.

Government attorneys and conservation groups that had sued to force a decision filed court documents Thursday settling the lawsuit and agreeing to the deadline. That came more than four years after a federal judge chastised government officials for rejecting the views of many of its own scientists when it decided against protecting wolverines in 2014.


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