In the waters of Peru, the anchovy could give way by the end of the century to much smaller species, according to an international study published Thursday.
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Peruvian anchovy is the heavyweight of global marine fishing. In the waters of Peru, this fish dominates the marine ecosystem. But by the end of the century, because of global warming, this species could give way to others, much smaller, according to a study published in The science journal , Thursday, January 6th.
Global warming has two major consequences on marine ecosystems. On the one hand, heat results in a decrease in oxygen present in water. On the other hand, it boosts fish metabolism, which then need more oxygen. But more the fish are fat, the more they have trouble oxygenating the cells located at the heart of their organism. In warmer oceans, so the size of the fish tends to decrease.
In the face of this observation, a scientific team composed of German, Canadian, American, Spanish and French researchers proposed two hypotheses: either facing global warming, individuals of the same species would see their size decrease; Either a change of community would be observed for the benefit of smaller species. “So far, it was impossible to determine which of these two hypotheses was valid, explains Arnaud Bertrand, researcher at the Research Institute for Development (IRD) and Coauthor of the Study, because the pressure of the fishery also causes These two phenomena. Difficult, therefore, to share things between climate and fishing. ”
Proliferation of small fish
To try to validate one of the two hypotheses, the researchers compared the size of the fish and the communities present on two distinct periods, using as a model ecosystem the current of Humboldt in Peru. This current is currently the most productive in the world and represents about 15% of the world’s global annual catch.
Thanks to the fossil fish bones found in marine sediments, the researchers first studied the species present during the last interglacial period, there is 130 000 to 116,000 years. At that time, temperatures and oxygen contents in Peru were similar to those predicted for the end of the century. Then they analyzed the ecosystems of Holocene, that is to say the last 1100 years. “Balance sheet: In the last interglacial period, individuals of the same species were not smaller, explains Arnaud Bertrand. For example, anchovies had the same size as during the Holocene, from 12 to 19 centimeters.”
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