Bob -
Good questions. The short answer is yes they have been considered and to date have been found to be of limited value. Conditions (both river systems and fisheries) are different here than in the Great North.

Let's consider salmon and steelhead separately.

For salmon much of our salmon fishing occurs well out in front of the rivers. If in-season updates relied on river counts they would be too late to effect the fisheries - most of the fish would have been caught before they got to the river.

Theoretically steelhead would be easier as nearly all the fishery is in-river. The fly in that ointment is the water conditions, especially for winter steelhead. Our frequent floods in October through Febraury would make reliable counts difficult; who knows how many fish may or may not slip into the river during a week or more of high water.

As you point out the technology is improving as it does hopefully counters will prove to useful as well as affordable. Stay tuned.

Tight lines
Smalma