January 7, 2022 — In 2008, a team of researchers boarded an expedition vessel and set sail for the anchovy-rich waters off the coast of Peru. They were searching for a place to extract a sediment sample that would unearth secrets about the ocean from 130,000 years ago, a time when the planet was experiencing its last interglacial period. About 130 kilometers (80 miles) north of Lima, the researchers found an ideal spot; they bore into the seabed and drew out a 20-meter (66-foot) core sample.
Over the next 13 years, researcher Renato Salvatteci and a team of colleagues worked to date the core and measure fish debris. They were trying to figure out what fish were living along the Humboldt Current system off the coast of Peru during that interglacial period, when the ocean contained little oxygen and was about 2° Celsius (3.6° Fahrenheit) warmer than the average temperature experienced in the current Holocene epoch — conditions that almost match what scientists project for 2100 as climate change rapidly transforms our modern world.
Today, the Humboldt Current contributes to more than 15% of the global annual fish catch, mainly due to its abundance of Peruvian anchoveta (Engraulis ringens), a species in the anchovy family. It’s also what global conservation authority the IUCN calls “the most heavily exploited single-species fishery in world history.”
Every centimeter of the sediment held an astonishing amount of information — about 90 years’ worth, said Salvatteci, a fisheries engineer at Kiel University in Germany. What they found embedded in the ancient sediment wasn’t anchoveta, but the vertebrae of “considerably smaller” fish, such as mesopelagic and goby-like fish, that were able to cope with the low oxygen levels in the water. They published their findings in Science on Jan. 6.