Todd,

Please don't take this wrong as I'm not implying that dessicating redds is a good thing. However, at this stage, the eggs can withstand being de-watered for up to 8-10 hours as long as they are recharged afterward. Often there is substantial water under the redd where the eggs are deposited that would appear to be de-watered on top.

I don't know what the procedure is for PSE and whether they have time constraints to recharge redds at certain elevations. That would be a good question to ask.

I do know that several years ago, a fairly well known flyfisherman (and biologist) moved to Concrete and documented the de-watering of chum redds when there was some miscalculation of available water to be release that left chum redds high and dry.