Generally, all fish in the shoal have roughly the same dimensions. At the sight of hundreds and even thousands of similar fishes predator difficult to focus on a specific production. So choose their fish kompashku individuals of the same size with them, and they do so, as it turned out, the smell.
Researchers from Mount Allison University and the University of Sydney conducted several experiments with fundulyusom and stickleback. Zoologists traced the fish respond to different chemical signals from individuals of different species and sizes. According to the experts, to obtain samples of odors was not difficult because the fish continually release into the environment any molecule.
Scientists have discovered that fish are more attracted by the smell of fish of similar size to them. And the size of the individual, as the researchers note, is even more important to fish than its species identity. Thus, sticklebacks preferred to smell them equal in size fundulyusa than other sticklebacks that were more or less of it.
Based on these results, zoologists have concluded that the smell of fish are able to assess the size of other individuals and to compare them with their own parameters. What substances can fish with olfactory receive such data, scientists have not yet figured out. They believe that this may be the products of metabolic pathways that are somehow tied to the size of the body of the individual.