Fish face a new threat — ocean acidification caused by global warming. In a recent study published in Global Change Biology, researchers found that warming waters and acidification could adversely affect how fish interact in groups.
The project leader, Professor Ivan Nagelkerken from the University of Adelaide’s Environment Institute and Southern Seas Ecology Laboratories, says that tropical species are traveling toward Earth’s poles and finding new ways of interaction. “Fish show gregarious behaviour and cluster in shoals which helps them to acquire food and for protection against predators,” said Nagelkerken. “Many gregarious tropical species are shifting poleward under current ocean warming and interacting in new ways with fish in more temperate areas.”
Researchers reviewed how fish species interact and behave in changing environments. They aimed to determine how the rising concentration of carbon dioxide in the atmosphere affects fish behavior. With CO2 already driving global temperatures high, oceans and seas have also been warming up. When the oceans warm, they also get acidified, which affects the behavior of fish and other sea creatures.
“We found that tropical and temperate fish species tend to move to the right when coordinating together in a shoal especially when spooked by a predator, but this bias significantly diminished under ocean acidification,” said Angus Mitchell, a University of Adelaide Ph.D. student who was among the researchers.
The study found that mixed shoals of tropical and temperate species were less cohesive under warm ocean conditions. They also showed less interest in escape, raising concerns over the coexistence of predator and prey. Professor David Booth from the University of Technology, Sydney says that these responses from fish are a result of stress from interacting with new species and having to stay in new territories.
“Our findings highlight the direct effect of climate stressors on fish behaviour and the interplay with the indirect effects of new species interactions,” said Booth.
According to said Nagelkerken, the survival of certain fish species is threatened under these conditions. “Strong shoal cohesion and coordinated movement affect the survival of a species: whether to acquire food or evade predators,” said Nagelkerken. “If the ability for fish to work together is detrimentally affected it could determine the survival of particular species in the oceans of the future. Tropical species may initially fare poorly when moving into new temperate areas.”
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