“CJ’s flies ” The Preston Jennings Isonychia Nymph

The Preston Jennings Isonychia Nymph


Isonychia Nymph

Article, Photos and Flies by “Catskill John” Bonasera

“Kahil’s Rainbow Lodge, the Phoenicia Hotel, Five Arch Bridge, “the Portal”—these are all associated with only one Catskill river, the Esopus. Running wide and fast, the Esopus has the distinction of being permanently off-color due to fine-grained red clay deposits found in and around its drainage area. Depending on the release from the Portal, it can run from slightly off-color to downright muddy, but it has one of the best populations of wild rainbow trout in the Catskills, if not the best.

Preston Jennings was a regular in the Esopus region and stayed at the area hotels. It was likely in this area that he first tied and tested his Isonychia nymph, a nymph that can be “fished like a wet fly.”

The Isonychia is a fast-water swimming nymph that moves more like a minnow than like a insect. Iso nymphs are very prolific in the Esopus, and it’s easy to see why Preston Jennings’s imitation was called by some of the patrons at Kahil’s Rainbow Lodge the “Esopus Nymph.” Jennings once gave one to an angler staying at Kahil’s with the advice to “fish it like a wet fly, because it’s the only nymph that swims.” The angler later caught a dozen trout in the next hour using that fly.

A friend of mine, guild member Ed Ostapczuk, has lately been using this nymph with excellent results on his favorite sections of the Esopus using the “swing and twitch” method. His success prompted me to try it, and on a recent trip, I caught my first Esopus rainbow on one.

The beauty of this fly is its simplicity. It really is a basic nymph, tied “in the round.” Since there is no wing case, it looks the same upside down as it does upright.
The Preston Jennings Isonychia Nymph


Hook: Size 8 or size10 nymph hook. Jennings used both sproats and snecked hooks, but a 1X-long or 2X-long nymph hook is fine

Tail: Tip of a partridge feather

Rib: Round gold tinsel

Abdomen: Seal’s fur (or a substitute, these days), dark red and plum, mixed

Thorax: Peacock herl

Hackle: Furnace cock hackle, two to three turns and short


Jennings also tied this fly with a peacock sword tail (three fibers and short), a full body of dark claret seal’s fur mixed with black wool, no peacock herl thorax, and one to two turns of grouse for the hackle.

This is a great fly to carry with you on almost any Catskill stream, because the Isonychia is a common mayfly that hatches from early summer to mid fall. Fish it in riffled water and let it swing straight down, induce a little rod-tip twitch. and hang on!”

One Comment Add yours

  1. Tristan says:

    Very interesting subject, thank you for posting.


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