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 Thus spoke the WIZ ...  ff@ homepage

Subject: Changing flies - the San Jaun Lesson
To: Multiple recipients of list FLYFISH

G'day All

Lots of new children so a short bio then to the point;

List father
Grandfather of the 22 OBA
Midge fisher -dry that is
Senior Water Scientist USEPA
area of expertise Water Quality Monitoring and the use of midges in rapid bio-assessment (Reprints of Pubs available to other bethnologists).


The Point:

Midges are the most taxa and individual rich group of aquatic macro invertebrates in any stream. Nematodes may out shine them but they are not macro inverts. Not at all uncommon to collect 30 + different taxa emerging in a single 24 hour period. Over a years time have recorded 60 + species from Kansas stream! Knew of stream with in excess of 120 taxa. Density wise are often in the 1,000's per square meter.

What would happen if all the different taxa tried to emerge at the same time? They would get in each others way. competition reduction and resource partitioning is the name of the game. Segregate the emergence of different taxa temporally both on the short term (daily) basis and longer term (month/season) basis. If they do this they "Don't get in each others way' as they try to escape the surface film and not all instars trying to order the midge equivalent of a big mac at the same time. Some want happy meal, some hamburger and fries and some want to go out for pizza.

Intellectually I've know that, but fishing wise it didn't occur to me until my one and only (never to be repeated) trip to the San Juan. I was giving a paper at NABS -North American Bentholigical Society - meet being held in Santa Fe. Took advantage of being there to fish the San Juan after the meeting. Right off the bat I took two nice Rainbows - nice as to size not as to how they looked - on what else but a 22 OBA. Fish were still gulping in the run but I could not buy or lease a fish. Frustrating to say the minimum.

Hanging my head in shame, I noticed several dark dun/almost black size 24 midges crawling on the legs of my waders. Switched to a 22 black midge and started getting rises again. Then the rises to my fly stopped but the fish were still rising. Looked down again and this time it was a cream midge, which thank you sweet Jesus, was about size 20. Switched again and fish on again. This whole series occurred over about 4 hours.

The reason hit me. Reduce competition and partition the resource. Different taxa emerging at different times of the day when their unique environmental requirements were being meet. Trout were not willing to take the weird midge in the drift.

After emerging, midges head for shore and hang out in the trees until it is time to do the "Mating Swarm". My guess is that brown chest waders look like tree trunks to midges. Not the smartest of taxa.

I've had somewhat similar experiences with other groups of insects, but not to this extent. Over the day you may be a bit more successful if you change size or body color on a Caddis - generally the generic 16 or 18 olive EHC will catch as many fish as other typical sizes or colors. and of course you need to have an 18 PMD for the hour of that hatch or a 22 Trico for the spinner fall.


Thus spoke the WIZ

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