The survival and eventual return of juvenile Snake River salmon and steelhead to spawning streams as adults depends more on their size than the way they pass through hydroelectric dams on their migration to the ocean, new research shows.

Bypass systems are designed to carry juvenile salmon and steelhead around dam turbines on the Columbia and Snake rivers. The study found little evidence fish that go through these systems suffer delayed or "latent" mortality once they reach the estuary and ocean. Rather, they survive at about the same rate as fish that go through spillways and turbines.