Codfish onslaught: Millions of capelin fall in mass predation
According to IFL Science, scientists have observed the largest single incident of capelin predation they have ever documented. Over the span of four hours, millions of codfish attacked the capelin school, killing 10 million fish.
Capelin, or Mallotus villosus, is a small fish that inhabits the waters of the northern Atlantic. It feeds on plankton and krill. IFL Science notes that capelins are an important part of the food chain, with a role similar to anchovies in warmer waters.
Threat from predators
Mallotus villosus are vulnerable to predators while searching for spawning grounds. The greatest danger comes from codfish, which, during their migration to their own spawning grounds, prey on capelin along the way.
An article published in the journal Communications Biology states that MIT scientists, using Ocean Acoustic Waveguide Remote Sensing sonar, detected a gigantic school of capelin that extended for dozens of kilometres. According to estimates by Nicholas Makris from MIT, the school might have consisted of 23 million fish weighing about 413,000 kilograms.
Capelin did not previously form schools
Capelin gathered in such a large group to achieve a similar speed and maintain a common direction of movement. While schooling behaviour is known among many fish species, it had not been observed in capelin before, according to IFL Science. However, this large concentration of fish makes the capelin school an easy target for predators. Scientists calculated that during the observation using the mentioned sonar, approximately 10.5 million capelins were killed.
– This is happening over a monstrous scale, and we’re watching a wave of capelin zoom in, like a wave around a sports stadium, and they kind of gather together to form a defence – said Makris. According to the scientist, the same is happening with predators. – [They are] coming together to coherently attack – he added.
While the scale of this event is gigantic, it does not threaten the capelin population. However, it is significant that rising global temperatures may make some capelin spawning grounds unsuitable, forcing the small fish to concentrate in fewer locations, which could increase the risk of predator attacks.
