Only about 10 percent of the fry make it to this stage and are called smolts. Smolts are especially vulnerable. They are frequently injured or killed by turbine blades and the extreme pressure changes experienced when passing through the turbines of dams. In addition, smolts float downstream tail-first and depend on the river's current to flush them to the ocean quickly. The slack water created behind the dams is very difficult for the young fish to negotiate, making them vulnerable to predators.
Dams also slow the migration considerably.
A trip that used to take one to three weeks can now take one to three months, depending on the beginning point of the trip. The smolts have limited energy stored in their bodies and may run out before they are able to reach the ocean. Up to 90 percent of the salmon hatched never reach the ocean. The smolts that complete the journey downstream spend several weeks in estuaries where the river meets the ocean, feeding on small fish and shrimp. Eventually, they disappear into the ocean where they grow to adulthood.