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Re: Nymph Survey Through the Seasons
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Having re-visited the three riffles last month (July) that were surveyed in April, the results across the three streams showed noticeably fewer macros. While I expected to find fewer and smaller nymphs in summer, this drop was more pronounced than I had predicted.
Here are the results for July:

CONOCOCHEAGUE:
Mayflies:4
Caddis: 3
Stoneflies: 0
Scuds and Cress Bugs: 0
Crayfish: 1

YELLOW BREECHES:
Mayflies:38
Caddis:1
Stoneflies: 0
Scuds:48
Cress Bugs:0

LETORT:
Mayflies: 1 (very small)
Caddis: 0
Stoneflies: 0
Scuds: 6
Cress Bugs: 26
Other: 3 Crayfish, 1 Worm




Posted on: 8/13 10:52


Re: Nymph Survey Through the Seasons
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In particular, note the steep drop off of mayflies at all locations.

While one would expect to see fewer nymphs due to hatching in the previous weeks, this suggests that opportunistic trout may be more likely to be focused on other forage species.

Breeches, for example, dropped from 78 mayfly nymphs in April down to 38 in July. On Conococheague, mayflies dropped from 18 in April down to 4 in July. Letort mayflies dropped from 13 down to just 1 very small nymph.

In addition to such drops in numbers, the mayflies were notably smaller at all stations.

Cress bugs were much fewer at Letort, however I should note that seining Letort was hard this summer. Unlike Breeches and Conococheague, which had lower water levels this month, Letort was choked with weeds in the survey riffle and water levels were actually much higher and slower than in the spring and this may have impacted the number of macros captured.

A brief side observation is that crayfish increased since springtime.

Posted on: 8/13 11:01


Re: Nymph Survey Through the Seasons
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Will return to these spots in October and check again.

After the final survey in October, I'll re-capitulate the results and write up a conclusion. This may be posted in article format on the home page.
DW

Posted on: 8/13 11:02


Re: Nymph Survey Through the Seasons
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The survey is complete. I made a small adjustment and did the autumn survey early in November rather than October. The results for November are:

BREECHES:
Mayflies: 29
Caddis: 6
Stoneflies: 0
Scuds: 43
Cress Bugs: 1
Other: 1 crayfish and 2 worms

CONOCOCHEAGUE:
Mayflies: 9
Caddis: 19
Stoneflies, Scuds, Cress Bugs: 0
Other: 1 worm

LETORT:
Mayflies: 5
Caddis/ Stoneflies: 0
Scuds: 50
Cress Bugs: 109
Other: 1 crayfish, 4 "blood worm" midges, 3 worms



Posted on: 11/12 20:55


Re: Nymph Survey Through the Seasons
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Once again, the results verify the observation that nymphs in these streams are, generally, quite small. Most of them were under a quarter of an inch in total body length this month, and many were much smaller. I placed a few in the viewing trays to be photographed and these were often among the larger specimens that I was able to get a hold of. The upper image shows some macros from Breeches in November and the lower image is from Letort for comparison....

Attach file:



jpg  YB Nov1.JPG (132.79 KB)
13138_5a08fc4ce04a2.jpg 600X349 px

jpg  Letor Nov 2.JPG (146.42 KB)
13138_5a08fc56c832a.jpg 600X305 px

Posted on: 11/12 20:58


Re: Nymph Survey Through the Seasons
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Great info, Dave. Thanks for sharing.

I would guess that most of us have way too many mayflies initiations in our fly boxes and ones that are a lot larger than the actual insects inhabiting the stream.

Lesson learned.

Posted on: 11/13 7:01


Re: Nymph Survey Through the Seasons

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Great post Dave I have to make sure I follow this one for now on.

Posted on: 11/13 12:30
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Re: Nymph Survey Through the Seasons

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Thanks Dave, very illuminating.

Posted on: 11/13 15:35
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Re: Nymph Survey Through the Seasons

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I'm wondering how much bias (of the distribution of types) is built into the results by sampling in riffles rather than pools. I would expect that species that feed on rotting leaves to be under represented, for example. Also, how many caddis get missed because they're firmly attached to rocks? (It would have been interesting to divide caddis into cased vs free living.)

I'm not saying the data you have isn't valuable, just wondering what your thoughts are about biases?

At any rate, thanks for taking the time to do this.

Posted on: 11/16 10:08
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Re: Nymph Survey Through the Seasons
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Results posted in the PAFF blog.

And Tweeted to the PFBC site here.

Posted on: 11/17 7:12


Re: Nymph Survey Through the Seasons
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Quote:

redietz wrote:
I'm not saying the data you have isn't valuable, just wondering what your thoughts are about biases?

At any rate, thanks for taking the time to do this.


This is worth noting and a good point: the methodology - kick seine in riffles - would likely select more for certain species. For this reason, many macro surveys include, in addition to the seine, manual examination of rocks and woody debris. For reasons of time I simply had to limit the locations and survey methods. Perhaps in the future, we can follow up on this survey with larger sample sizes/methods and more waterways(?).

Regarding caddis, the surveys did reveal a good number of them and in Concocheague caddis did outnumber mayflies by a small percentage during January and November. Some evidence of caddis cases did turn up in the siene but I did not count them in the bug totals unless an actual nymph was visible. These cases were mostly grannom "boxes."

Posted on: 11/17 8:36


Re: Nymph Survey Through the Seasons
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One thing often overlooked by anglers seining for bugs or turning over rocks to determine what to tie on their tippet, is how often will these creatures end up in the drift and be available for fish to actually feed on?

Many/if not most of these macros, especially the immature ones, will stay hidden from fish under rocks until they are ready to hatch.

A more useful utilization of the info gleaned would be the prediction of hatches in the future - ie, if you find a bunch of immature hendrickson nymphs in the winter, that's the place to be in April during the hatch.

In addition, as mentioned above, many macros are hidden in the substrate, in weeds or roots or wood or maybe found in deep water.

It's fun to check out the bugs in the stream, If you do it often enough, during different seasons and in different places on a stream, you can get a handle on what the macro population consists of in that stream. This will allow you to make a more informed decision on what fly to fish that day, and maybe more important where to be when the hatches occur.

......or just use the "Mo" method > fling out a pink worm and hope


Posted on: 11/17 9:27


Re: Nymph Survey Through the Seasons
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I don’t know why you gotta poke me in the eye to make your point. I am one of the biggest proponents of turning over rocks. And to your point, there is a thing called biological/behavioral drift that occurs at sunrise and sunset for about an hour where the “homeless” macros roam the currents looking for new places to habitate.

Some of those are aquatic worms of the pink variety...I hope anyway.

Posted on: 11/18 9:24
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Re: Nymph Survey Through the Seasons
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Quote:

afishinado wrote:
......or just use the "Mo" method > fling out a pink worm and hope


I'll pile on and poke Maurice in his other eye....

Kidding aside however, aquatic worms were prevalent in this survey. If you go up a few posts (#35) to the November Letort photo, you can see some worms. The tiny red midge larva are obvious but also in that tray is a typical worm. The worms I found in my seine looked just like conventional earthworms in form and color, however they were very small, usually only about 1-2" in length and 1-2mm in diameter.

Also of note, although they were never numerous, worms were present in all seasons.

Posted on: 11/18 9:53


Re: Nymph Survey Through the Seasons

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Quote:

Maurice wrote:

Some of those are aquatic worms of the pink variety...I hope anyway.



http://www.nwnature.net/macros/worms.html



Posted on: 11/18 10:00



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