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Fly Fishing

> Fly selection, Page 2

Fish don't have hands, they sample potential food with their mouths, or cheek or jaw -at least that's what it looks like. I even got to see this with trout I kept in an stream tank. If you've ever watched drift feeding trout you'll see them "sample" objects (grass, pine needles, trout flies...) both visually, bumping with jaw or cheek, and taking into the mouth. The result for non-food items is usually rejection, but not always.

One chapter of my dissertation is about this sampling issue in juvenile Chinook salmon. Sampling really hasn't been documented well in the scientific literature, and models of trout feeding energetics don't take into account the opportunity cost of sampling non-prey items and potentially missing real prey. It might be a small cost for large fish that see relatively little debris of the same size as their food, but it's pretty significant for the little fingerlings that feed on 1-2mm prey all the time. That's because there's so much more debris/detritus in the drift that matches the size of their prey. I'm giving a talk on this at the American Fisheries Society meeting in Seattle this fall, and hopefully publishing a paper on it soon thereafter.

"Selective" feeding is an energetics game and a time when they are NOT sampling, being satisfied with the results and chowing down.

I'd like to do some professional work on this in the future, hopefully really soon as a post-doc. I've done some preliminary modeling on it already and it's a really interesting issue.