With water bodies so low .The kokanee must spawn in shallower sections of the lakes, when the lakes rises to winter levels, kokanee reds will be in deeper cold water. Do you think this matters for the kokanee survival?
Careful about the assumptions about temperature at depth. The densest fresh water happens at 4 degrees C - not zero. In the winter, many lakes in Canada have a colder layer on the top (verses the bottom at 4C). Deeper (in the winter) often means warmer verses colder water. Then there is also groundwater upwelling through redds, as well. Often, it is quite a bit warmer than the ambient lake water. So - many factors to consider - but you can bet the spawning fish know this all better than us.Don't have any research for you but I doubt it would adversely impact their survival.
Probably take longer for eggs to hatch in colder water but not sure how many ATU's required for them.
They've survived thousands of years so far and most likely had similar conditions in the past.
The opposite scenario would be bad however, particularly if their redds dried up.
Because they are fall spawners that is highly unlikely though, given our normal precipitation levels.
Take care.