A video captured by photographer David Palfrey reveals an incredible method of defence by a school of fish.
Many shark species inhabit the Ningaloo coral reef off the west coast of Australia. In a video posted in 2017, photographer and diver David Palfrey offered us the unique spectacle of one of these sharks (possibly a grey reef shark or a copper shark) diving into a school of fish. The latter, in response to the attack, responds very peculiarly, forming into a ‘ball.’
The bait ball technique
Although the interaction between the shark and the school of fish seems calm on the video, the predator is looking for food. In response to the attack, the school of fish narrows to adopt a formation called a ‘bait ball.’ This strategy has the advantage of facilitating the communication between the individuals of the group and allows them to confuse the predator.
When sardines migrate
Such a phenomenon is also observable during the sardine run which takes place between May and July in South Africa. At this event, billions of pilchards from California gather to undertake the long journey from the Aiguilles Bank, near Cape Town, to the city of Durban, in the east of the country.
During this journey, sardines are exposed to sharks, dolphins, sea lions and sea birds, to which they provide a prodigious source of food. It is then that it is possible to observe the emergence of these bait balls, intended to protect the group and limit the number of victims during assaults. In the field of military strategy, it seems that Man is not the only one who has these defensive formations.
Check out the video above to see the incredible 'bait ball' technique for yourself!