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As our world warms up due to climate change, changes in the ocean could have a devastating effect on the fish we eat, a study has found.
German researchers reconstructed an ancient warm period – the Eemian interglacial period of 125,000 years ago – using sediment samples from the Humboldt Current System off Peru.
This period was similar to what some climate predictions have suggested our world could be like by the end of this century – and the study's results show how climate could affect the fish we eat.
Scientists found that at warmer temperatures, smaller, goby-like fish species became dominant and pushed back important food fish such as the anchovy.
The researchers warned that warming, acidification or oxygen depletion may have significant consequences for the composition of fish stocks, including the displacement of individual species.
They said that the greater warming of the Humboldt Current System as a result of climate change has more far-reaching implications for the global fishing industry than previously thought.
Around 8% of the global catch of marine species comes from the areas off the coasts of Peru, where the near-surface Humboldt Current provides a high nutrient supply and thus sufficient food for commercially exploited fish species, such as the anchovy.
Catches of anchovy in the Humboldt upwelling system are currently declining. The causes of species shifts are mainly due to climate change, according to the results of the study.
In the period 125,000 years ago, conditions were similar to those predicted by climate projections – such as the IPCC report – for the end of the 21st century at the latest.
Lead author Dr Renato Salvatteci, of the Center for Ocean and Society of the Kiel Marine Science (KMS) in Germany, said: "The conditions of this past warm period that we were able to reconstruct from our samples can definitely be compared to the current development and put in context with future scenarios.
"According to this, there is a clear regime shift towards smaller fish that feel more comfortable in the warm, lower-oxygen conditions. We conclude from our results that the effects of human-induced climate change may have a stronger influence on the evolution of stocks in the region than previously thought."
Professor Ralph Schneider, a paleoclimate researcher at the Institute of Geosciences at Kiel University and co-author of the study, said: "Our studies using sediment cores can give us fairly accurate information about the changes and their dynamics in highly productive coastal waters around the world that have occurred in the wake of different climate states and over different time scales."
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