MIT captures the largest inter-species murder in the ocean. Millions of creatures died in four hours

In the ecological key, nature almost always moves forward with two protagonists: the prey and the hunter. We call this game of cat and mouse mixed endings to discover each person’s interests, and in Xataka we have told many stories with wolves, sharks or hyenas, among others. However, none of the scenes resemble those seen in the North Atlantic. Scientists have captured an impressive and unusual massacre in the open ocean.

Unprecedented death. Every year, millions of capelin (anchovy-like) fish migrate to the coast of Norway to spawn (release their eggs), attracting many predators along the way. During one of these migrations, MIT scientists observed the largest hunting activity ever recorded, where millions of cod attacked a large school of capelin, eating about 10.5 million of these fish in just four hours. Took.

This phenomenon, fascinating for various reasons, has been the subject of a study published in Nature that has allowed researchers to observe the population dynamics of both species, activities fundamental to the marine ecosystem in the North Atlantic.

Capelin and its role. The capelin, the reluctant hero of this story (Melotus villosus) is a small fish that feeds on plankton and krill in the cold and productive waters of the North Atlantic. This species plays an essential role in the marine food chain, as do anchovies in warm waters.

Although their abundant populations have suffered declines in the past, they have a trick that saves their demography: the large number of eggs they produce allows them to recover more quickly than other species. Is. However, this abundance also makes them highly vulnerable to predation, especially during migration to spawning areas in the gravel of the sea floor at depths of two to 100 metres.

Science and monitoring. As reported by MIT, the researchers used an advanced sonar technology called Ocean Acoustic Waveguide Remote Sensing (OAWRS), with which they were able to follow the movements of these fish over a wide area in real time. He says that in the early hours of 27 February 2014, OAWRS revealed how the capelins, initially scattered, grouped into a huge school of 23 million individuals.

This grouping phenomenon allowed scientists to observe the natural behavior of capelin, which manage to coordinate their movements when they reach a critical density.

Banks and hunters. As we said, although forming schools allows capelin to save energy and in some cases avoid predators, this concentration also makes them a very attractive target.

Thus, as huge schools of capelin formed, a group of cod, estimated to number 2.5 million fish, began “hunting”. The scientists observed that density waves running through both populations appeared synchronous, reflecting a dynamic interaction between predators and prey on an unprecedented scale.

How does it matter? The more unique the incident recorded, the more important it is. Although this type of mass hunting does not pose a direct threat to capelin populations, as their annual migration to the area involves billions of individuals, scientists express some concern about the impact of climate change.

The reason? Apparently, the loss of breeding areas due to rising global temperatures could limit the safe places for this type of species, which, in turn, could have serious consequences for the entire North Atlantic marine ecosystem in the wheel that is nature. .

Bonus Ball: Understanding Marine Life. The sonar technology used, OAWRS, is able to differentiate between species by different resonance frequencies, and this has allowed scientists to accurately identify the signals of each type of fish.

As Nicholas Makris of MIT explained, fish’s swim bladders emit a bell-like resonance. Thus he concluded that the sound of cod is deep, while that of capelin is high. This difference has been important for detailed study of these large-scale hunting events and opens the door to a better understanding of marine ecology.

Image | pot, Nicolas Makris, et al

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