Salmon
The migration of North Pacific Salmon from the Ocean to their freshwater spawning habitat is one of the most extreme migrations in the animal kingdom. The life cycle of a salmon begins in a freshwater stream or river that dumps into the ocean. After spending four or five years in the ocean and reaching sexual maturity, many salmon return to the same streams they were born in to spawn. There are several hypotheses on how salmon are able to do this.
One hypothesis is that they use both chemical and geomagnetic cues that allow them to return to their birthplace. The Earth's magnetic field may help the fish navigate the ocean to find the spawning region. From there, the animal locates where the river dumps into the sea with the chemical cues unique to the fish's natal stream.
Other hypotheses rely on the fact that salmon have an extremely strong sense of smell. One hypothesis states that salmon retain an imprint of the odor of their natal stream as they are migrating downstream. Using this memory of the odor, they are able to return to the same stream years later. Another smell-related hypothesis states that the young salmon release a pheromone as they migrate downstream, and are able to return the same stream years later by smelling the pheromone they released.
Read more about this topic: Natal Homing
Famous quotes containing the word salmon:
“There are some achievements which are never done in the presence of those who hear of them. Catching salmon is one, and working all night is another.”
—Anthony Trollope (1815–1882)
“The first man to discover Chinook salmon in the Columbia, caught 264 in a day and carried them across the river by walking on the backs of other fish. His greatest feat, however, was learning the Chinook jargon in 15 minutes from listening to salmon talk.”
—State of Oregon, U.S. public relief program (1935-1943)