Posted by Jim E (69.92.166.54) on January 20, 2005 at 19:22:04:
The hatch triangle
The triangle applies to all hatches and thinking of a hatch in this way can help you better understand what ALL is really taking place during that hatch. Most know the life cycle stages of aquatic insects. The stages important to the fisherman and the fish are: nymphal or larval (depending on the insect), then the pupae or emerger (again depending on the insect) and then the dun or adult. I’ll leave out the spinner stage of mayflies since it is really not part of the hatch. What the triangle is intended to represent is the amount of time that each of the insect’s stages are available to the trout.
(Don't laugh at my drawing...please !!!)
Long before duns or adults of a particular insect are seen, their nymphs/larvae are becoming active. They are moving around a lot and venture out of their normal hiding places. Many succumb to the current in their haste of anticipation of the things to come. When things are just right (known as degree days) for some of these, they will begin to emerge or pupate. Other nymphs are still active but their “degree days” haven’t added up yet thus their emergence will be at a later day. So, during a day’s hatch, only a handful of the active nymphs progress onto their next life stage. So you see why nymphs make up the bigger, bottom part of the triangle, they are available over a much longer period of time. Next would be the emergers and pupae.
As one would determine from the above, this stage of life, the middle of the triangle, is pretty short lived. Insects don’t remain in this stage for long. Better measured in minutes rather than days. But what an important stage this is, with many fish preferring to feed on these rather than the soon to come adults.
Then, for the insects still lucky enough to be alive, comes the adult stage. Representing the top of triangle, adults/duns can be gone in a flash, quickly taking to flight, while others must wait awhile until their wings dry. Either way, these insects aren’t sticking around for long and are only available to the fish for a short time.
So what does this all really mean and why is it important ?
Well, it tells us how important nymphs are. Always !!! There is almost always some nymphs or larvae easily attainable to the fish. Where as, emergers and adults can be scarce at times. To possibly put some percentages to it (un-scientific mind you) I would say that nymphs are available 70% of the time, then emergers 20% and adults 10%. So it stands to reason that we should fish accordingly, nymphs 70% of the time, emergers 20% and so on. Now, as with all fishing, other factors can and do come into play. But as a general rule of thumb these percentages would be a good guide. This triangle fact might also explain some fishing “I don’t know why’s”.
Often I’ve said, “there were bugs hatching all over the place yet there were no risers”. Does that mean the fish weren’t there ? Probably not. They may well have been feeding on a different stage of the hatching insect and I was so enamored by the adults that I didn’t even try nymphing through the area or try fishing some emergers. Another thought for consideration is we know that often, surface feeders are the smaller fish that are in the area. This can be much for the reasons discussed last week in Fish’s security and other reasons too. But it doesn’t mean larger fish aren’t there and taking advantage of the food abundance. I’m as guilty as anyone else, if there is a chance of catching fish on dries, I’ll try it. But one has to wonder what size of fish would be produced if some careful nymphing was done during a hatch ?
What has your experience been ?
Thanks for reading.
Jim Enns <*;))))))))))))><