Posted on July 12 2016
Musings on March Browns and Isonychia's - (the times they are a changing).
Back 15 years ago, before everyone needed a drift boat to trout fish there were two attractor flies that you needed to fish the Delaware River system. Early season it was the March Brown and from June first on it was the Isonychia. March Brown takes on the water were marked by explosions spraying water a foot into the air. Isos came after most people had left the river and catching fish on them was a foregone conclusion. You threw either fly, in season, and the fish ate it.
Fast forward ten (yes I said ten) years and the river was covered with guides in drift boats. What were their clients throwing if there wasn't a specific hatch on? You guessed it. Were they catching fish? Yes, but probably fewer every year that they did it. Why? You'll have to trust me when I say I've done some experimenting with trout in my pond and yes, they can remember things - even from year to year! Assuming you are willing to believe this, (I KNOW it's true) picture a brown trout of 18 inches and probably five years old. He has eaten many tasty March Browns and Isonychias but he has also felt the sting of the barb on far too many of them. In fact the number with the stinger has increased every year of his life. He doesn't eat either of them much anymore. Perhaps one or two when the hatch begins but then when he gets stung he switches to the nymphs and leaves the duns alone.
Fast forward again to 2016. How many fish were eating March Browns? Several guides I talked to said "The March Browns are hatching but the fish aren't on 'em yet", they never were. They have learned over the years that both flies are bad medicine. I know a spot where the current takes drift boats away from a pocket of water that holds half a dozen trout. The spot is also hard to get to for wade fishermen. I fished it twice this year during March Browns. First time I hooked all six fish on a March Brown dun. One week later I went back and rose but two of the fish on the same fly. One turned away at the last minute and the other came up and gave me an indignant refusal. They remember!
It's the same with the isos. I haven't caught ten fish on isos all year. On two occasions I was fishing on the big river in a good iso hatch with duns all over the water and never saw a one eaten. The fish are taking the fast swimming nymphs with those splashy rises you see.
The guides? I don't float but I know most of them have their clients thwapping and splatting with a bobber and nymph rig instead of throwing attractors. The DRC blog says people are having success floating isos in the riffles. I am too. Anyone can float isos in the riffles. The trick is to get fish to eat them with any regularity. Right now you'll catch more fish throwing a Cowdung or a Wickham's Fancy!
The fishing today you ask? It wasn't worth talking about.