flies for anadromous fish

I enjoy tying flies and fish them. There is nothing more fun than "made up" a fly and use them to catch a fish. You might ask, if the fly is not resemble a regular food item, why fish eat them? Currently, the "field theory" from those steelhead and salmon fishermen says, it might be other motivation than food acquisition. It could be aggressions that provoked by mimic mate stealer? it could be aggressions that toward the egg stealer? or it might be just curiosity? As a behavior ecologist myself, I believe it is all possible. Some fisherman examined the stomach content have found that a lot of steelhead did not have anything in their stomach. This confirmed the previous thoughts that anadromous fish did not eat after enter the freshwater. However, some samples did recover some food items in the steelhead stomach. Some eggs, feathers and some aquatic insects... so they do eat, or at least they do "swallow" something, if we tend to call "eat" is a kind of behavior which is actively seeking food items and consume it in order to extract energy from it. So, good news to us, as soon as they swallow something, then there is still hope for fisherman to catch them, in the form of hook and line. Noted, the high percentage of empty stomachs is interesting. Those fish does not eat, or does not eat recently before they got caught. This totally make sense to me, why would you eat in the place that was poor of food item? the reason you original leave the river for... (seeking food items in the ocean is one of the explanation that some steelhead become anadromous fish species, while some steelhead remain in the poor nutrient river and remain small (trout life form)). So no eating interest, low food abundant...made up high percentage of empty stomach. However, here is question, if they happen to see some food items in front of them. do they eat it? the scenario is you are enter a class and happen to find out it is a surprising b-day party prepared. Do you going to eat the cake, even it is no where near the eating time? I don't know... maybe yes, maybe no? But will you touch it or smell it just to exam how good is this cake, if it worth a bit? What I think this later scenario is more likely in steelhead... the touch and feel it bit light bite "short strike". I have seen a lot of bass doing this short strike when examing the potential food items. That is the place olfactory cue and textile cue come together... I am guess steelhead and other salmonids are doing the same... ever wonder the experienced steelheader tell you to put the trailing hook all the way to the tail of the fly? because there are going to have a lot of short strike if you don't do so. (to be continue...)