Fleaflickr02,

In an environment where a salmon population cannot replace itself, meaning that 1 spawner always produces less than 1 recruit, there is no such thing as an MSY escapement goal. The management concept of MSY assumes both population productivity and an environment that facilitates that productivity. That is what allows "surplus production", that number of fish over and above spawning escapement that can be safely and reliably harvested without threat to future production.

In a case like the Stillaguamish, or the model's Simuguamish, the spawning population, no matter how small or how large, simply cannot replace itself on an average annual basis. It's an environment that necessarily leads to extinction. Were it not for the Stillaguamish Tribal hatchery program, Stillaguamish Chinook would have likely gone extinct before now, or would be hovering dangerously close to it.

At extremely low population levels, like the Stilly, it can be possible to a population to hang on for years. This can happen by the few spawners using the very best of the overall poor habitat, and the resulting fry using the very best of extremely limited juvenile habitat. In such a case, the population is functionally extinct, but not factually extinct.

Sg