The mortality rate of the species varies according to the conditions of the habitat.
When the water is warm, mortality is higher, and it varies from 2% to 10%. This is how we see that phenomenon: a harvested salmon will die 100% of the time. However, 90% to 98% of those that are put back in the water survive. So, there is an advantage to doing that. When fishers do that adequately, survival rates are higher.