Researchers have shown that embryos and reproductive adults are more susceptible to ocean warming, so fish would be at much higher risk from climate change than previously thought.
In the worst case (5 ° C global warming), up to 60 percent of the world’s fish species would not be able to cope with temperatures in their geographic range by 2100 . Even if humanity meets the difficult goal of the Paris agreement to keep warming at 1.5 ° C, it would be too much for 10 percent of the fish.
The researchers analyzed the existing scientific literature on the heat tolerance of 694 species of freshwater and marine fish species .
Broodlings and embryos were found to face a much smaller gap between minimum and maximum temperatures, on average 7.2 ° C and 8.4 ° C respectively, than the 27.5 ° C range for adults.
The main reason why embryos and broodstock are less tolerant of ocean warming is due to their higher oxygen needs. Oxygen is more soluble in colder waters and less soluble in warmer waters .
Fish are important for human nutrition, so this study makes a strong case for protecting our ecosystems and natural environments, argues Hans-Otto Pörtner of the Alfred Wegener Institute in Bremerhaven, Germany, who is part of the team behind the investigation.
Unfortunately, the seas are expected to warm too fast for evolutionary adaptation. While fish can move to colder regions, suitable new spawning sites are not always available. "It is worth making an effort to achieve as little climate change as possible," says Pörtner .