March 20th, 2000

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Behaviorial Triggers
Literature & Streamside Observation

By Ron Koenig

The other evening Old Rupe briefly stopped by the chat room , a rare occasion these days, and brought to everyone's attention an excerpt from Caddisflies written by Gary LaFontaine where he mentions a conversation he had with another good friend of our's, Dr. Rich Colo. In the course of that conversation Dr. Colo, (herein after referred to as Rich,) and Gary discussed a theory about a trout's feeding preference with regards to a dominant eye.

Caddisflies was written in 1981 almost twenty years ago. Ten years later a book called Trout from the Wildlife Series was written by a group of scientists from varying backgrounds all of which involved 'Salmonoids'. At the time of that work, it was a commonly held notion that trout would hold in a given stream or other body of moving water for periods recorded up to as long as three years, siting several reasons such as stream hydraulics, cover and superior feeding opportunities. It was further stated by this group of scientists that in the event the occupying trout, if for some reason was relieved of his position that a trout of similar size, prowess and preference would move into the vacated position.

It is widely accepted by most fly fishers that hatch, insect size, insect color and the stage of the emerging insect are key factors in determining the proper fly required to improve ones production on the stream. It is also widely accepted and frequently debated as to weather the flawless presentation of the properly selected imitation takes prescience over the exactness of the imitation. Taking into consideration the three basic reasons a trout will strike an imitation, to obtain food, to protect it's territory and curiosity, we are left with more questions to ponder at stream-side.

Recently, I read of new findings that show trout will move as much as two and a half miles in a given stream in a given day. This new information causes me to wonder, does the trout always pick the same side of the stream or it's preferred object for cover when it arrives at a new location in the stream? Are trout left finned or right finned, as it were? What about if the trout that's been use to a bank-side position takes up a position in the center of the stream, will it take up a position that has a rock on the same side of it as the bank was when it was previously closer to the bank or migrated to a different part of the stream?

Another book, Trout Tactics written by Joe Humphreys, also published in 1981, suggests that if the angler sights a trout, his first cast should be behind the trout, the next two casts should be to either side of the trout and the last cast should be in front of the trout. I have watched this activity on many occasions from vantage points above and behind trout that were suspended in the water column. It's been really close to call as to whether a food item sometimes falls directly behind and above these fish but it seems they knew when a food item was even in their 'blind spot.'

Now the hearing ability of the trout comes into play. Could it be that a trout can determine to some extent what the food item may be just by the sound of it hitting the water. I've read and/or heard it said that a trout's hearing is so acute that it can hear a nymph crawling on the stream bottom. Could it be a trout's attention is first drawn by sound when it involves a food item and that the trout can expect and recognize a certain food item to enter it's window before it does? Humans, as most other mammals, can recognize these sounds, we've all heard the snap of an aluminum can open from a distance before we can actually see it, or the rustling of a snack food bag, the list goes on. Is it possible a trout having heard a food item hit the water, will reposition itself to take that food item because he knows what it will be before he actually sees it, just how far off his feeding station will he go and will the trout only view that food item with it's dominant eye?

I've seen trout do strange things from time to time and I'm convinced they're as individual as we are. I think if I were standing in front of a buffet table with a variety of items I preferred, the hand I picked them up with would only be determined by which hand held the plate.

Another observation I had the privilege to witness last fall was to see a trout come out of the water to take a low flying dragon fly that was zipping across the surface very quickly only three inches or so off the water's surface. I was amazed , almost stunned. I couldn't help but appreciate the reflex time of the trout nor could I help wondering if the trout could hear that dragon fly above the water and how far away. It seems impossible that the dragonfly would have been in the trout's window for more than a nano second.

Rupe, thanks for the boot in the butt to start me pondering, Rich, thanks for the point to ponder. ~ Ron Koenig (aka Osprey)

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