Facts about the salmon river

Spawning stock target and harvestable surplus. A salmon river can only produce a certain number of smolts that go out to sea to eat themselves. How does what we call the spawning stock target relate to harvestable surplus?

Spawning stock targets and harvestable surplus

A salmon river can only produce a certain number of smolts that go out to sea to eat themselves. How does what we call the spawning stock target relate to the harvestable surplus?