Tipping Point in Humboldt Current off Peru Leads to Species Shift


Researchers reconstruct link between ocean warming and shift to smaller fish species using sediment samples from the Humboldt Current System.

Researchers reconstruct link between ocean warming and shift to smaller fish species using sediment samples from the Humboldt Current System.

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. They were able to show that, at warmer temperatures, mainly smaller, goby-like fish species became dominant and pushed back important food fish such as the anchovy (Engraulis ringens). The trend is independent of fishing pressure and fisheries management. According to the study, the greater warming of the Humboldt Current System as result of climate change has more far-reaching implications for the ecosystem and the global fishing industry than previously thought. The findings appeared in the journal Science, January 7.

The sea off the west coast of South America is one of the most vital and productive fishing grounds on earth. Around eight percent 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. Ten percent of the total global catch of anchovies alone comes from the region. Much of it is processed into fish meal and oil and used primarily for aquacultures in China and Norway. However, 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 new study.

Researchers from the Institute of Geosciences at Kiel University, together with colleagues from GEOMAR Helmholtz Centre for Ocean Research and international partners, have for the first time investigated the relationships between temperature, oxygen, nutrient supply and the occurrence of individual fish species using paleo-oceanographic data from the Humboldt Current region. The scientists focused on the warm period about 125,000 years ago (Eemian interglacial). During this time, conditions were similar to those predicted by climate projections (e.g., the IPCC report) for the end of the 21st century at the latest: comparable primary production but water temperatures two degrees Celsius higher than today and increased oxygen deficiency in mid-depth water masses.

Read more at Kiel University

Image: Fishing vessel off the coast of Peru in the Humboldt upwelling system, one of the most productive ecosystems in the world. (Credit: © Martin Visbeck, GEOMAR)