There is another interesting piece about behavior and survival. In looking at the downstream, within stream, survival of smolting fish from acoustic tags the data I saw had similar mortality rates, per mile migrated, for hatchery and wild fish. I ascribed this to the fact that when the fish smolts it changes its behavior, position in the water, and probably even suite of predators going after them. So, there is a learning curve for all of them as they switch.

In some cases, the hatchery fish suffered less loss over the same distance because they were mass planted and overwhelmed the predators. Wild fish dribbled out.