Do you want to save the salmon|? Is it salmon first? If you want to save the salmon ban all sales of in the wild caught salmon. Just like our terrestrial dwelling wildlife. Let the natives harvest there half to feed the village. just do not allow sales to markets. No one raping the resource for money.

Make it like deer, elk , ducks, ect. It is available for harvest, but if you want to eat it you have to go harvest it.

This will never happen, but if it did, it would pretty much fix it.