Re late spring Hybrid Trout spawn run at Henry's Lake Outlet (between the dam and US 20). Usually many fisherman wading and a few were bank fishing. Is wading is legal or not? Is wading a significant threat to newly laid eggs? No signage either way?

There are no restrictions on wading below Henrys Lake.  While there are many redds visible, and many anglers wading through the stream (and even through redds), it is rare for impacts from wading to have enough of an impact on egg to fry survival to reduce fish populations.  In general terms, the number of fish living through their first year of life is dictated by other factors aside from egg survival success.  In many instances (and particularly in a harsh environment like Island Park) winter conditions dictate how many fish survive their first year of life.  As such, anglers wading through redds won't decrease the number of trout that eventually recruit to the population. If you are fishing the Outlet, please remember that the upper 1/2 mile flows through private land on both sides of the river.  As such, it is important to stay in the water, and not get out on the river banks.