Scientists have learned how itchy fish
Sockeye salmon often jumps out of the water and flies a considerable distance from the edge. It’s not a game, but an attempt to get rid of blood-sucking parasites, and while quite successful, found by biologists.
Spawning sockeye salmon (Oncorhynchus nerka) is a spectacular sight: bright red fish jump out of water to a height of 30 cm and are up to a meter of water. Quickly turning tail fins, each creature jumps out of the water an average of nine times a day. Fish do not jump obstacles, do not maneuver so for they seem to fly over the water. This week, the scientists published a study that explained that sockeye salmon jump and fly not from good life: it turns out they are trying to get rid of parasites.
And wild and farmed salmonid fish, including sockeye salmon suffer from a small parasitic crustaceans of the family Caligidae that live between the scales and the fish take a lot of inconvenience.
In a previous study on this subject concluded that the jumps and flights on the surface is the way the fish itch. Unknown remains, however, whether it helps to get rid of parasites.
In the new experiment, the scientists closed the aquarium with one group of the fish mesh so that they could not rise above the surface. Three days later, the scientists counted the fleas, and found that those who could jump in and beat on the water bore almost one-third less parasites.
The results, published in the Journal of Fish Biology, suggests that the jumps do help the fish to cope with parasites — although it cost them dearly.
Jumping out of the water, the fish become easy prey for birds and other predators, and also wastes energy. But what will they do to scratch where they itch.
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