I should note for perspective that my home water, tail waters in the upper Delaware, enjoy the full panoply of famed Eastern mayfly emergences. Paraleps, Quill Gordans, Hendricksons and related species (E.subvaria, invaria, unclassified "X", etc.) all the wonderful Stenos...March Browns, Grey Fox and Cahills, followed by E. cornuta (#14 BWO), Sulphurs (E. dorothea) locally called Doros, Green and Brown Drakes, tricos and all the smaller summer insects too (psudocloeon, baetis, etc.). Not to mention stoneflies from the tiny early blacks to the giant Eastern Pteronarcys and all those caddis flies too. I am leaving many out and no doubt miss spelling many too. Further, the upper Delaware watershed enjoys a Culture of Aquatic Entomology. Though he no longer owns it, Al Caucci of Hatches fame, trained many of the guides and anglers on the River out of his former, Delaware River Club and Fly Fishing School, and instilled a serious sense of mayfly-centric head hunting in them. Anglers including the commercial guides do not keep bankers hours during the mayfly season on this river, regularly staying out into darkness to meet specific spinner falls. When you read the DRC's daily river report blog, the current hatches are referred to by their Latin names. This is not a river where "Buzz Balls" and "Fuzzy Faces" are knotted onto tippets; this is a 5' of tippet and match-the-hatch environment both for angling effectiveness and cultural appropriateness. Even the local bar and burger joint remains open and cooking until the last angler is off the water with lots of camaraderie and lies peaking around 11PM.
The greatness of the upper Delaware fishery is a man made function of New York City having built bottom release dams for urban water supply on a formerly marginal trout and small mouth bass fishery. Its wild strain non-migratory California rainbows and European brown trout were introduced in the 1880's and hung on until NY came along and built its dams so they might flourish. Not that this was the City's intent and a continuous battle between urban water use planners and conservation and fly fishing organizations is waged...I will be in attendance in a NYC restaurant for a new combat offensive tomorrow morning. In the Delaware's case, mayflies need not have been stocked as its watershed enjoys, in its headwaters, famed trout streams like the Willowemoc, Beaverkill and Neversink and many lesser known streams from which to recruit the broad spectrum of classic hatches...not all dam created, cold tail waters have such resources.
Great tail waters like the Bighorn are isolated from quality trout streams and therefore lack, not habitat, but entomological diversity that they could easily and beneficially support. In the majority of our man-made quality fisheries, none-native browns and rainbows had to be introduced for us to enjoy the angling opportunities we enjoy today. Why not mayflies?
West Branch of the Delaware in May