Err, before suggesting things are simply just based on Gaussian distributions, you may want to read the text.... The curve is actually a shape in which the lower population values show a very static recruit to spawner (nearly a level curve) until a "minimum" threashold is reached. Then from there, the value becomes asymtotic to a maximum carrying capacity. The neat thing about the curve is the resiliance of the population to mortality, yet it's complete crash and stasis below the critical threshold. I believe the specific values you are talking about are the MSY and MSH curves which are quite a bit different than what I was talking about. I think the biggest thing about this should be noted. I didn't disagree for the orginal cause of the Hood canal crash. Insteady I suggested that the ability of the fish to rebound in the "habitat intact" areas around hood canal was a poor example.