Thanks for the replies (and pictures).

So according to Sg there is an upper size limit for which a gill net is effective, consistent with what I was told (by a different biologist). It would make sense those few larger fish I've encountered that appeared to be net-marked were fish too large to fit into the mesh past the gill plate (especially if mesh size had been dropped to 5" for winter steelhead-targeted fisheries). A maimed fish is more likely to spawn than a dead fish, but I would be interested to see how much difficulty a fish "too large" has in navigating past a series of interleaved nets, and what sort of consequences would be expected for survival/fitness, especially if there was a holdover period involved (e.g., spring chinook, sockeye, summer steelhead).

I haven't taken many measurements on fish, but I'm imagining 12" girth equates to 5 lbs. or so - so fish from 13" at the dorsal on up to 13" at the gillplate (with a "fusiform" body, maybe 18-20" at the dorsal?) would seem caught one way or another. Thus the expected composition of fish upstream of the net is lots of 4-6 lbers, with a few 18-22 or more; or in a population that never had 18-22s, just the 4-6 lbers. Semi-accurate?

Time to go think about something else.

-IS