Monday, January 17, 2011

What fishes see

Have you ever wondered exactly how a fish sees your bait in the water?  I have, and this weekend I decided to figure out one aspect of how the fishes see.  I'm mostly a fly guy, so I pulled out my dry fly box and selected some of my main patterns to check out.  I know a lot of serious fly tiers will have some sort of viewing box set up permanently and will do this often, but I never have and found the results fascinating.

What I really want to watch somehow is how nymphs tink along the bottom of the river.  I'm not sure at this point how to go about viewing and recording that, so instead I'll just take a look at how dries sit on top of the water.  This is a much simpler observation to make.  I had to come up with a makeshift viewing box with the few materials I had lying around the house.  I chose a clear glass pie tin, and to support it I pulled a rack out of the oven.  The result was very high tech.  I turned my coffee table on its side, then placed the oven rack across one leg and the side of the top.  Finally, the pie tin with a little water in it went on top.  Done and ready!

Don't feel bad that you never thought this contraption up, I am quite smart.

Next I think it's pretty obvious:  toss a fly in and take a picture from below. It's pretty easy.  The only thing I'm still not positive on is how to light the fly correctly.  My first assumption is that fish will see your fly differently in different conditions.  Maybe that's obvious.  I think the best way to simulate a sunny day is by putting a small halogen lamp somewhere up above but probably not directly above.  That was what I did first and here are the results.  The flies are, in order of appearance, a sz20 midge dry, sz16 para-BWO, a sz18 LBF dry (see my recipe), and a 14ish stimulator.

And I have drawn some conclusions from these simple pictures.  First the top one is a size 20 and is almost too small for me to see any detail.  Thus, I conclude that in a midge hatch it's probably most important to get the size about right.  Maybe that's common knowledge but I just discovered it.  The way my brain works you can tell me this bit of info a number of times and I will forget it every time.  But now that I see why it is likely so, I've got it stored in my brain.

Another conclusion that I surprised myself with in this experiment is that I no longer like parachute flies!  The big circle of hackle that is wrapped around a post sticking out of the top of the fly doesn't look like anything.  At least in the normal style of dry where the hackle is wrapped around the hook rather than above it looks like legs.  Granted it looks like about 50 legs whereas a real bug will probably only have 6, but at least it can be mistaken for legs.

Finally, it really seems that color won't matter much on a sunny day because all the fish will see is the shadowed bottom of the fly.  The shade, as long as it's not way off, will probably not have much affect.

Writing all this makes me remember a seminar I sat in on a long while back at the Denver fly fishing expo where the guide said we should chose our flies based on "size, shape, and shade" and in that order.  Size is most important, shape should at least be reasonably close to a real bug, and shade is just that: shade.  Not color, not exact shade of gray, but general shade.  Meaning don't use a white fly where you need a black, but also in nearly all circumstances don't worry about using a black rather than olive, tan rather than gray, etc.  Again, I have to see it to really believe it and I am now a believer!

That's what those flies look like (hopefully) to a fish on a bright sunny day, but I'm not sure how to simulate a cloudy day.  Probably the best way would be to have a very brightly but diffusely lit room, but I don't have any of those nice photographer's umbrellas or very bright lighting so I'm just going to see what the fly looks like lit from the bottom.  I have a suspicion that on a cloudy day the fly shade may actually be tougher to see because instead of looking up at blank blue sky the fish is looking up at clouds which can be somewhat bright.  This is a challenge for another day, very soon I'm sure.

But if you are curious what some of these dries and others look like in water when well lit from below, here you are:

I bought the Adams (first picture) online a while ago and have always felt it has way too much hackle.  Seeing this pic, I still think that.  The LBF (second pic) looks pretty much the same except the gold hook is extremely visible!  I recently acqiured some black hooks that I like a lot more.  The caddis (third) I also bought online with the Adams and I think he hackle they used was about four sizes too big.  Other than that it looks reasonably close to what a caddis looks like (see below).  The sz20 midge is still really too small to see much detail.  I just hope fish don't have microscopic eyes.


  1. I am very impressed with your ingenuity here. Looks like you're getting some good information to take to the vice and river.

    I'm reading a very interesting book right now about this (keep an eye out for another book review). Well, kind of - the book specializes on bass and their senses. In one chapter it gets into the details on what a bass is capable of seeing...seems their eyes don't work exactly the same as ours and their world looks a little different. How closely trout resemble bass I can't speak about.

    Take it to the next level....Your pie pan shows the fly from a fishy's perspective, but doesn't really show you what the fish sees. I still think it is valuable to see flies from their perspective, but for the next experiment you should take similar pictures with the actual bugs. Even though we still wouldn't see what a fish sees, it would allow us to make conclusions on how closely the fly matches - that is the objective after all.

    Now, good luck finding some bugs.

  2. Oh, and you should add a blue or grey background.

  3. That is an amazing idea!! Thanks for posting this. Like your blog. I just started following