MIT Researchers Claim ‘Largest Predation Event Ever Recorded’ Occurred in Norwegian Waters During Spearfishing

They thus discovered an absolutely titanic act of predation, bringing together several million capelin and predatory cod.

The capelin spawning period

By studying a strip of ocean located off the Norwegian coast, oceanographers from MIT and Norway intended to collect information concerning the reproduction of capelin (a small fish from the Atlantic and Arctic Oceans, which is used in particular as bait for fishing for cod ).

These small fish, about the size of an anchovy, make the journey each year from the edge of the Arctic ice cap to the Norwegian coast, where water temperatures and conditions are more suitable for spawning their eggs. eggs, (the spawn). Thus, every year, billions of people undertake this journey, to reach water whose temperature is “between 6 and 10°C” according to the Government of Canada.

A school of 23 million individuals

MIT scientists studied the capelin schools, which extend for tens of kilometers, using a “ultrasound-based wide-area imaging technique”, as relayed by Phys.org. “The dense schools of capelin instantly imaged are estimated to contain approximately 23 million individuals and weigh 414 tonnes,” specifies the study.

In response to their grouping, the specialists realized that cod were also starting to group together… until they also formed a gigantic school of 2.5 million fish according to the specialists' acoustic mapping. This school of predatory cod crossed the school of capelin, consuming, according to analyses, more than 10 million fish. All this happened in just a few hours.

Dramatic consequences for the marine ecosystem

“Cod are estimated to consume approximately 10.6 million schooling capelin […] This equates to a total consumption by cod of approximately 0.1-0.2% of the Barents Sea capelin stock in 4 hours”specifies the study. This could be the largest predation event ever recorded.

This event alone is not enough to weaken the capelin population, however the Arctic ice cap is retreating due to climate change. Consequently, the journey for capelin to reach its spawning ground will be lengthened. This will make it more vulnerable to natural predation phenomena.

Problem: capelin, although very small, is absolutely crucial for the marine ecosystem. The consequences of a weakened capelin population could be dramatic for the species that depend on them. “Our work shows that natural predation disasters can alter the local predator-prey balance within hours.”concludes Nicholas Makris, professor of mechanical and ocean engineering at MIT.

Source: Communications Biology