esshup,

I am missing the last link in your reasoning why we can't sustain our FHM populations?

How do they lose their shallow water safety net during winter?

Is it your X inches of ice freezes solid their thickest shallow plant cover? Is it snow cover on the ice stops photosynthesis and they lose ALL of their plant cover?

I am asking to determine if there is any way to make "refuges" where at least a portion of the FHM population can survive past the first few years.

I have to clear cedar trees on our land almost every year. I was thinking about some small cribs where I stuff in two small cedar trees every few years. If a few FHMs can survive over the winter, could they get at least one significant breeding event in the spring when the maximum plant cover again provides them some safety net?