The short answer is that a specific amount, or more, of fish must die. Hatcheries, which sustain most Chinook and coho salmon fisheries in WA can be harvested at or above 90% of the return and still have enough eggs for the next generation. Anything above the egg-take needs is wastage. The co-mingled wild fish can't withstand that level of harvest and many of the harvest groups are opposed to fishing selectively.

Due to chronic overfishing, significant destruction of the habitat, and little support to deal with the basic problem of too many people and too many people who want to eat salmon, we have those hatcheries.