Fish Monger,

A few days after completing spawning, female steelhead begin migrating back downstream. They brighten up a lot after spawning also. The fungus would eventually kill the fish, or lead to other complications that will kill it. But if it reaches salt water soon enough, the fungus doesn't survive in the salt, and if the fish survives the readjustment to salt water, it will regain its health quite rapidly. Assuming, of course, that a seal doesn't grab it in its weakened condition. More females survive to spawn a second or third time because a male after spawning just goes looking for another female so that no female goes unspawned for lack of a mate. Males are so worn out when they finally head back downstream that far fewer of them survive compared to females.

Sincerely,

Salmo g.