The young salmon instinctively follow the same creeks and rivers used by their ancestors as they make their way during spring runoff to the ocean. As they travel, they undergo a physiological change. Once they reach the mouth of the stream or river, the fish remain in the salty bay for several months, feeding on tiny shrimp, other crustaceans, and the young of other saltwater fish. They grow rapidly, and eventually move into the open ocean. Just how far a salmon travels in the ocean, and the direction it heads, will vary.
Many salmon follow the circular flow of ocean currents.
Some fish will migrate as far as 2,000 miles from their home stream, while others will remain closer to home. To help even the odds, the salmon feeds mostly at night, when it is harder to see. After maturing, and spending most if its life in the ocean, the salmon migrates back home to spawn in the same river or stream in which it was hatched. This journey is very difficult, and salmon have to fight their way upstream, over rocks, past waterfalls, and around human-made obstructions such as hydroelectric dams. Salmon are guided on this journey by the smell of their home waters, which they can detect from among all the other smells in the downstream flow.