After a few years spent at sea, salmon returning to the rivers, and the fish are just exactly the river, from which they emerged. Such amazing peg to the house is not only the fish — just old place turtles, seals, whales and dolphins. The question is, how do they manage so well find their way home?
According to researchers from the University of Oregon (USA), when returning home salmon use a magnetic map. That is fish remember the magnetic field of the Earth. Test this assumption scientists managed thanks to a happy occasion. On the west coast of Canada is Fraser River, which originates in the Rocky Mountains and flows into the Pacific Ocean. But at the point where they exit into the ocean is pretty big Vancouver Island, so that salmon who are going up the river, we have to choose which side to avoid this piece of land from the north or from the south.
|The confluence of the Fraser River to the Pacific Ocean and the island of Vancouver, which has skirted the salmon to enter the river. (Figure Oregon State University.)|
Researchers analyzed data on salmon migration in the region, collected over 56 years, and compared them with observations of the magnetic field. The intensity and direction of the lines varies with time. And, as it turned out, the fish preferred to go that way, where the characteristics of the field were similar to familiar to them in the old days when only the salmon out of the river. That is, going into the sea, the fish remembered the look of a magnetic field, and then coming back, and remember it and compared to the current map. And chose the familiar "magnetic path", even if it did not coincide with the same geographic.
However, fish are native river even by smell. But the sense of smell works with them when they've sailed pretty close to the target. A home away from salmon, apparently, have to rely on a magnetic sense, at least as long as the smell will not be able to recognize the river. If we consider that in the past year, the trout found cells that respond to the magnetic field, the hypothesis that the ability of salmon to the geomagnetic orientation does not seem so improbable.
In the future, researchers are going to verify the data obtained by direct experiment. But in any case it is unlikely the fish rely on one sense. It is known that in the ocean, between the ocean and the river is the temperature differences that fish can also feel. So, most of all, to navigate in space and find their way home salmon helps complex sensory organs, among them the thermoreceptors, and olfactory receptors, and the magnetically sensitive organs. And this list may be incomplete.
The study is published in the journal Current Biology.
Prepared according to the University of Oregon.