Fish bond when they eat the same food, smell the same

London, March 23 (IANS) For some fish it makes more sense to swim around with those that share their taste in food – and smell similar in the process – than to shoal with members of their own species, finds an interesting study.

Chemical cues play a definite role in creating familiarity of smell and creating bonds between members of different species.

“The results suggest the general familiarity of shared chemical cues could be a way by which to induce shoaling behaviour between fish of the same and different species,” said Tanja Kleinhappel, researcher at the University of Lincoln in Britain.

Food and protection may be the reason behind the association with fish that smell the same.

“By associating with others that share the same preference for particular types of food, a fish ensures that it has enough to eat,” Tanja noted.

Being surrounded by similar-smelling fish also protects an individual against predators that use certain chemical search patterns to detect prey.

The shoaling behaviour of the fish is not controlled by visual or other non-dietary cues that are specific to a particular species.

But free amino acids — the building blocks of cells, tissue and muscle — may form part of the chemical cue that the fish are picking up on, the researchers observed.

Previous research has shown that free amino acids in the skin mucus of fish are very similar to those found in their food.

The study, published in the journal Behavioural Ecology and Sociobiology, reveals the underlying mechanisms that enhance social learning and information transfer.

The team analysed three-spined sticklebacks (Gasterosteus aculeatus) and nine-spined sticklebacks (Pungitius pungitius) from local rivers and streams to investigate how bonds between different species form.

In nature, these two species live side by side, yet individuals are also known to shoal together.

The researchers carefully planned what individual fish ate, and the groups into which they were placed.

Some groups contained members of both species that ate different types of food. In such cases, three-spined sticklebacks were most likely to associate with other fish with which they shared a diet – irrespective of the species their new found friends belonged to.

When all individuals in a group were fed on the same diet, the three-spined sticklebacks showed no particular preference to be with members of their own species.

“This behaviour is most likely mediated by the general familiarity of diet-derived chemical cues, as the fish were previously housed in different tanks and were unfamiliar to one another,” Tanja maintained.

To establish whether free amino acids indeed help individual fish to decide which others they want to associate with, further experimental work is needed, they concluded.

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