This species has seen millions of its individuals devoured over a very short period of time. An impressive event that could happen more and more frequently.
More than 10 million individuals of the same species were devoured in just a few hours by predators. A real butchery… This event which occurred in the Barents Sea, off the Norwegian coast, was studied by researchers from the Massachusetts Institute of Technology (MIT) and the Norwegian Marine Research Institute whose research was recently published in Nature Communications Biology. The team used an underwater acoustic detection technique, capable of mapping populations using sound waves. Specific frequencies allow different species to be distinguished.
The researchers explained that it was the grouping of the species that would have caused it the greatest harm. This school may have attracted predators and allowed them to devour more individuals at once. “This is the first time we’ve seen a large-scale predator-prey interaction, and it’s a coherent battle for survival,” observed MIT ocean engineer Nicholas Makris.
The prey devoured are capelin. These small fish migrate in groups from the Arctic to Europe every February to find more suitable conditions for laying eggs. “If they are close enough to each other, they can adopt the average speed and direction of the other fish they can sense around them, and can then form a massive, cohesive school,” explained Nicholas Makris. 23 million capelin were grouped together, forming a ten kilometer long school, and were attacked by 2.5 million Atlantic cod. In a few hours, they consumed half of the bench. Never before has such an underwater event been observed.
Although these figures seem considerable, the attack only wiped out 0.2% of the capelin population, which numbers in the billions. This being said, its role is important in marine ecosystems as prey of cod but also of seals for example. Reducing its population could have a domino effect on the species that need it to survive.
The researchers especially wanted to highlight that this type of phenomenon could worsen with global warming. As the ice melts, these fish must go farther and farther to find suitable breeding grounds, leaving them at the mercy of predators for longer. This is why researchers plan to use this technology more widely to identify places of intense predation and help preserve endangered species.