E. Invaria: The Light Hendrickson

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Hatch Information:

  • Mid-May thru June
  • Emerging Water Temp: 55-60 Degrees
  • #14-16 Tan with Olive and Yellow Cast Adult
  • 10.5mm Adult Nymph Length

Hatch Summary:

This hatch typically occurs from Mid-May through June on some area streams. These nymphs come in three main colors, some reddish brown, some black as night and others a darker olive. I found that the reddish brown and black varieties inhabited the same water whereas I found the olive colored nymphs on different streams. It is my thought that one of these three color variations is actually Ephemerella Rotunda. E. Invaia/Rotunda belongs to the Mayfly family of crawlers and as such it migrates from hiding places just prior to emergence, it is very productive to fish the nymph patterns for hours before the hatching occurs.  From discussions with other local anglers it is apparent that this hatch varies from stream to stream, some areas do not recieve much action and it was once worried that this hatch could be dissapearing from the area but conditions last season with minimal flooding have probably helped improve the outlook for this specie.

2009 Hatch Report:

I fished this hatch for several days from May 20th thru the first week of June, most on a single stream but I did have the chance to notice hatching occuring on several streams scattered across the driftless area in Southeast Minnesota. Hatching occured almost like clockwork close to 10:30am right as the water temp was hitting 59 degrees. I watched light hatching producing the random rising trout several days in a row making for some fun but inconsistent dryfly action. In the future I would probably fish a two fly rig with an emerger pattern sub-surface to help increase the number of strikes. I fished this hatch only during the emergence of the duns and saw not a single spinner hit the water, it may be that the spinner fall occurs later during the evening of which I fished little of or during the night, not sure on that one. Fish a smaller #16 size Pheasant Tail Nymph prior to hatching as these nymphs are abundant and free floating in the stream prior to hatching. Hatching lasted for a few short hours ending usually close to noon but tossing a dry fly could still exhibit a reaction from the fish for a few hours after an emergence.

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