The salmon hatches in freshwater streams and rivers but then begins an incredible journey of up to 5000km (3000 miles), first to the open sea and then to return to the same river in which it was spawned in order to breed. The salmon only makes the journey once —after spawning, it dies. The European eel makes the reverse journey. It spawns in the Sargasso Sea, in the western Atlantic, and its tiny larvae swim to the shores of Europe and North America, becoming lever’s (small eels) on the journey. They then spend several years in freshwater rivers and lakes before returning to the Sargasso Sea to breed. Whales also travel huge distances, this time in search of food. The tiny plankton that they eat is found more abundantly in certain areas during the year.
Salmon mostly spend their early life in rivers, and then swim out to sea where they live their adult lives and gain most of their body mass. When they have matured, they return to the rivers to spawn. Usually they return with uncanny precision to the natal river where they were born, and even to the very spawning ground of their birth. It is thought that, when they are in the ocean, they use magnetoreception to locate the general position of their natal river, and once close to the river, that they use their sense of smell to home in on the river entrance and even their natal spawning ground.
A whale shark has made the longest migration journey ever recorded travelling 12,000 miles across the Pacific Ocean. The large fish, named Anne by scientists, was tracked making the mammoth migration from near Panama in the south eastern Pacific, to an area close to the Philippines in the Indo-Pacific. Experts at the Smithsonian Tropical Research Institute followed her signal from Panamanian waters, past Clipperton Island and Costa Rica’s Cocos Island, en-route to Darwin Island in the Galapagos, a site known to attract groups of sharks. The trip was the first recorded evidence of a trans-Pacific migration route for the species of the largest living fish.
Marine biologist Dr Héctor Guzmán, who first tagged Anne near Coiba Island in Panama, said: “We have very little information about why whale sharks migrate. “Are they searching for food, seeking breeding opportunities or driven by some other impulse?” Genetic studies show that whale sharks across the globe are closely related, suggesting they must travel long distances to mate. An adult female can travel around 40 miles per day and can dive more than 1,900 metres.
Picture Credit : Google