1. Troutnut Forum
›
2. Fly Fishing
›
3. How many bugs is a Hatch?

on that little urban drain i love this afternoon, with the sun coming and going and temps in the mid 40s, i actually saw a real mayfly. had wings and two tails and all. sort of an elegant sand color, maybe an inch long, and flew past my head. how many more of them should i have seen before i switched to a likely colored Klinkhammer? i saw only the one.

no fish were eating off the surface, perhaps because of the noisy construction machinery about 50 feet from me--the park service in its wisdom is suburbanizing the whole thing, so these poor trouts' beautiful place is a work in progress at the moment. i tried the usual searching combos, gave up, and finally got some action on a white mini-bugger i learned to make at a local TU meeting. (mea culpa, mea culpa, i'm being seduced by effective streamers. most fun i've had in weeks.)

so, how many bugs is a hatch? when is it worth getting excited?

I suppose you mean how many bugs is a fishable hatch, which makes for an easier question people are less likely to get all philosophical about. Even then there's the question of what makes a hatch fishable, and I would say it's one in which an imitation of the hatching critter has a distinct advantage for catching fish.

That depends on the size of the bugs and their hatching behavior, as well as how spread out they are (spacially and temporally). The guideline I try to follow is that it's usually worth switching to an imitation if I can scan the water carefully and see at least a couple of the bugs in question at any given time (unless they're hard to see, in which case I just have to guess).

yes, fishable hatch was what i meant. thank you for a simple rule of thumb!

once heard the tale of an angler who would simply present his (likely) fly over and over until the fish decided there were so many, they must be worth a try. his offspring referred to it as "Dad's making a hatch." it takes so long to get a bite sometimes, i wonder if that's what i'm doing some days. now that could get philosophical...

Casey-

Looking at your question from a somewhat different perspective, one might ask what constitutes a catchable hatch. In that case, my orientation would be more closely tied to trout feeding behavior, than it would be to bug count. When a few trout are looking up, or perhaps more importantly, are coming up to (or near) the surface, for the express purpose of chasing/intercepting/sipping emerging insects, whether or not I can actually see any emerging insects, and independent of whether the trout are being drawn up by a single stage of a single insect species, or by a cornucopia of insect species and stages, this would constitute a catchable hatch.

So, by extension, when a particular bug is hatching like crazy, but trout show no interest it, or there are no trout present, that would constitute a uncatchable hatch. Conversely, when a particular bug only emerges occasionally, but whenever one does, a trout promptly snatches it, that would constitute a highly catchable hatch. However, I suspect all my drivel may just be evidence of a thought process fueled by boredom, and impaired by old-age-related oxygen deprivation.

I like what Roger had to say and can especially relate to his closing proviso...:)

I'd only add that as I see it, there are so many variables that the only real definition with any utility is that a fishable hatch is one that interests the fish.

One factor certainly is the fish's instinct to optimize nourishment intake while simultaneously minimizing energy expenditure. This is also known as the answer to the question: "In general, why won't trout in 42F broken water freely rise to a hatch that puts one bug past their feeding station every 3 minutes...:)"

Then there is the nature of the stream itself. Fish in your garden variety small infertile Appalachian freestone are going to have considerably lower threshold so far as the point where the intensity of a given hatch interests them than trout in a much more fertile limestone where there will always be another bug (or some other food source) along shortly. Trout in infertile streams do not have this luxury for the most part and have to be more opportunistic.


I agree with Jason that once we see a few bugs on the water, an imitation is worth a try. One good reason for this, especially over wild fish, is that trout seem to retain a memory (and even a preference)for a given insect even if only limited numbers of them are hatching, just so long as they have been sufficient over time for the fish to make the food association. This is why, for example, on a lot of PA streams, the sulfur hatch lasts as long into the summer as you want it to and the big deerhair ant hatch never ends...:)

Wow, there are some smart people on here. Hopefully by posting I will be associated with them.

-Shawn

Shawnny-

That was being facetious, right?

I'll rephrase something I posted earlier and have since deleted. I was on my way out the door and shoulda thunk a little more before hitting "submit post." :}

A serious question was behind my rambling though. Determining whether a catchable hatch is occuring comes from experience, instinct, and lucky guesses. Is it possible at all to put numbers on it based on stream size? Or are the numbers the closest one can come to explaining the gut feeling?

I'm not sure that numbers or stream size factor in consistently. I've seen very heavy hatches that were inexplicably ignored, and rather sparse ones that got the immediate attention of the trout. And I know small streams where hatches don't mean much and others (mostly, but not exclusively limestone) where they mean a lot. On the former streams, I don't mean to imply that the trout won't eat just about anything they can grab, I just mean that they rarely seem to focus exclusively on any one hatch in particular.

I think that the productivity of a stream influences the tendency to focus feeding on particular hatches, and that a trout's recent experience with a hatch is also important. But even these are hard to quantify in a reliable way.

I also think that there is often a numerical threshold that seems to focus more or less exclusive attention on a particular hatch or phase of a hatch. And our man Jason has worked out some very interesting calculations in that regard. But, I think that mostly applies to a trout's first seasonal encounter with a particular hatch.

I have a small objection to the term "catchable" hatch, since the hatch isn't really what you're catching. It just sounds awkward, and to be more accurate you'd need to say "hatch during which the fish are catchable," which sounds even more awkward. I'd rather stick with "fishable" and just be clear on what we mean by it.

Also, the characteristics of the hatch are just one of many factors influencing whether or not the trout are catchable, and different trout can respond differently.

Of course, "fishable" taken literally could apply to anything unless the river is frozen over and you lack an ice auger. But let's go with the common, idiomatic definition that a fishable hatch is one in which trout under normal conditions would feed actively on the hatching species. It's tempting to load the definition up with other little caveats and details, but I don't think it's necessary. I think we all know what we mean by the term.



That is a really good question. My academic background in mathematical modeling tells me you can theoretically put numbers on just about anything, but sometimes it's prohibitively hard.

This question is more about trout behavior than about the insect hatch, and that requires a lot more variables to model, even for a simple and generalized result. It also involves some tough decisions and unknowns about exactly what the trout is optimized for and how effectively it can distinguish prey from debris.

I worked pretty hard on a similar question (when should trout feed selectively?) a couple years ago for my final project in an ecological modeling class at Cornell. I had to strip the problem to the bare minimum parameters, but I got some pretty interesting quantitative results. They wouldn't work to actually predict how real trout behave, but they give some good (and I think correct) insights into how the important factors interrelate. I'll email you a PDF of the paper I turned in, which should be good food for thought if nothing else. (If anyone else would like to see it, just ask.)

Edit: I just posted this and saw Gonzo already referred to the paper I just described. These are the 'very interesting calculations.' He's right that technically my paper only models the first seasonal encounter with the hatch, but more importantly it doesn't consider past or future encounters at all, meaning it's probably just as bad for the first hatch as it is for the others. It doesn't get quite that nuanced.

Facetious? There are people on here referring to scientific papers they've written on the subject! No, Roger, I was only being facetious in regards to myself. You guys blow my mind, truly.

(Now I've posted twice. Is it clear to everybody by now that I'm contributing valuable insights to this discussion?)

-Shawn

I would hesitate to call my class project a scientific paper! Normally that term denotes a peer-reviewed paper, which mine certainly is not. I did get an A, if that counts.

Nobody outside the angling world, to my knowledge, has studied selective (or, as Gonzo says, fixated) feeding behavior in trout. Understanding that behavior in detail doesn't carry a lot of management implications, so there doesn't seem to be much funding or interest in it from a scientific viewpoint. (Plenty of scientists personally think it's really cool and would probably like to study it, but it's low on their priority list as professionals.)

That has always been clear to me, Shawn.


Thanks for that, Jason. I know that this will remain a distinction without a difference for most, but I appreciate the reference. ;)

Or a difference without a distinction.

Hey Casey-

Didn't you once say that you had never caught a fish on a Wooly Bugger? I suppose it was inevitable, but welcome to the club! ;)

this is an amazing place. one can post a real beginner's question and get:
1) a pretty good, really simple answer for a "rough guide",
2) a lot of amazing scientific discussion about that answer,
and 3) someone with a very long memory who turns the thread just a bit.

yep, after catching a couple of bonefish in Florida, and thus learning exactly what is meant in fly fishing circles by the verb "strip", i applied the same vigor to the action on my 3 wt. and Wham, there was a fish. that is truly seductive, especially to one who loses fish constantly to not reacting properly when that splashy thing happens out where my dry fly probably is, or when the little fluffy indicator disappears momentarily.

also, that white number was a good deal flashier than anything i've tried before. now i know why the worm-drowners also use "spoons." Get the behind me, Satan!

now that i know there really are mayflies down there, i'll go more prepared. drifting those babies is a lot more serene, even cerebral!

Maybe, Casey, but I suspect that a white Wooly Bugger's mesmerizing influence on stocked trout (especially recently stocked trout) will always be hard to beat. Still, give those fish a chance to figure out what's what, and more serene and cerebral offerings will have their day. :)

>Still, give those fish a chance to figure out what's what, and more serene and cerebral offerings will have their day. :)>

Until it rains and you can't see the toes of your boots if you're in past your knees.

Then the white wooly bugger is king once again!

Not to disparage the serene and cerebral in any manner, of course...:)