Fundamental changes in the ocean, such as warming, acidification or oxygen depletion, may have significant consequences for the composition of fish stocks, including the displacement of individual species. Researchers at Kiel University (CAU), together with colleagues from Germany, Canada, the USA, and France, have reconstructed environmental conditions of the warm period 125,000 years ago (Eemian interglacial) using sediment samples from the Humboldt Current System off Peru.