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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

Dorsal view of a Sweltsa (Chloroperlidae) (Sallfly) Stonefly Nymph from the Yakima River in Washington
This species was fairly abundant in a February sample of the upper Yakima.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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Millcreek has attached these 5 pictures to aid in identification. The message is below.
Area of the Russian River where the nymphs were collected.
Millcreek
Healdsburg, CA

Posts: 344
Millcreek on Dec 1, 2014December 1st, 2014, 11:33 am EST
I'm pretty sure This is Epeorus longimanus but want to leave myself a little room to weasel out if I'm wrong since some Epeorus species are undescribed as nymphs in California. Among the nymphs that are described it could only be E. longimanus, E. grandis or possibly E. permagnus although E. permagnus hasn't been reported in California yet. E. grandis and E. permagnus can't be differentiated from each other as larvae. Both are much stouter in appearance than E. longimanus and the head is abruptly expanded anteriorly. These three species have the first pair of gills meeting or nearly meeting on the venter of the nymph. On the other described species of Epeorus in California the gills do not meet or even come close to meeting.

The nymphs were collected from the Russian River March 2nd, 2013 in riffles with a clean substrate of large gravel and cobble. All the photos are of nymphs in alcohol. The pictures were taken within 12 hours of collection so the color is close to that of live specimens. The nymphs are 8.5 mm long (excluding cerci).
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein
Entoman
Entoman's profile picture
Northern CA & ID

Posts: 2604
Entoman on Dec 4, 2014December 4th, 2014, 7:13 am EST
I haven't noticed it mentioned in descriptions but grandis has much shorter and stouter tails. Could this be one of our coastal species? Though it seems to comply with the keys, E. longimanus is found higher and more inland I think. They need pretty cold water.
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman
Millcreek
Healdsburg, CA

Posts: 344
Millcreek on Dec 4, 2014December 4th, 2014, 7:46 am EST
Kurt -

Could this be one of our coastal species?


I don't see how it could be unless it's a nymph that's undescribed. I've got several vials of these little critters and they all show the same characteristics. As far as I know the only Epeorus on the west coast with the first set of gills meeting or nearly meeting underneath are E. longimanus, E. grandis and E. permagnus. The other species of Epeorus, the Epeorus albertae group don't have the first set of gills meeting underneath.

They need pretty cold water.


They tend to show up pretty early in the year when water temps are cooler here (40-55 F) and disappear when temperatures get much higher. They're also quite common in some of the smaller tributaries of the Russian and tend to stay there a longer period of time (possibly due to the cooler water temperatures because of the canopy on the smaller creeks).

Food for thought,
Mark
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein
Entoman
Entoman's profile picture
Northern CA & ID

Posts: 2604
Entoman on Dec 4, 2014December 4th, 2014, 8:06 am EST
Interesting... I would think the water too warm for them, especially in the late Summer. Perhaps the eggs or early instars have adapted coping responses unique to this strain? I agree about albertae. The femoral maculae are wrong as well.

Do you have access to any descriptions of hesperus or lagunitas?
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman
Millcreek
Healdsburg, CA

Posts: 344
Millcreek on Dec 4, 2014December 4th, 2014, 8:32 am EST
Perhaps the eggs or early instars have adapted coping responses unique to this strain?


I suspect they are in the hyporheic zone, which is cooler.

Do you have access to any descriptions of hesperus or lagunitas?


Just a general description in an unpublished SAFIT account where they are lumped into the Epeorus albertae group. The key says this group does not have the gills meeting underneath.
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein
Entoman
Entoman's profile picture
Northern CA & ID

Posts: 2604
Entoman on Dec 4, 2014December 4th, 2014, 9:06 pm EST
Yeah, they have to be somewhere.

BTW, didn't mean to insinuate those other species were options - just hoping as an aside that you may have uncovered some nymph descriptions I was unaware of since we were talking about The genus. :)
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman
Millcreek
Healdsburg, CA

Posts: 344
Millcreek on Dec 8, 2014December 8th, 2014, 6:04 pm EST
Sorry -
I had a stroke the other day and haven't had a chance to answer, will
answer when I feel better.
Mark
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein
Martinlf
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Moderator
Palmyra PA

Posts: 3047
Martinlf on Dec 11, 2014December 11th, 2014, 8:32 pm EST
Mark,

Hope you are better soon. Let us know when you get a chance.

--Louis
"He spread them a yard and a half. 'And every one that got away is this big.'"

--Fred Chappell
Millcreek
Healdsburg, CA

Posts: 344
Millcreek on Dec 14, 2014December 14th, 2014, 5:53 am EST
Louis-

I'm feeling much better. I'm able to type much better. Don't feel nearly as clumsy as I did. Couple more days and I should be as good as new.

Mark



Kurt-

Will attempt to answer your question as soon as possible. Should be in the next couple days,

Mark
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein
Entoman
Entoman's profile picture
Northern CA & ID

Posts: 2604
Entoman on Dec 14, 2014December 14th, 2014, 6:21 am EST
Take your time, buddy. It's Steelhead season and this is the first chance I've had to check in anyway, so no hurry. Glad to hear you're feeling better!
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman

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