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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 Ephemerella mucronata (Ephemerellidae) Mayfly Nymph from the Yakima River in Washington
This is an interesting one. Following the keys in Merritt R.W., Cummins, K.W., and Berg, M.B. (2019) and Jacobus et al. (2014), it keys clearly to Ephemerella. Jacobus et al provide a key to species, but some of the characteristics are tricky to interpret without illustrations. If I didn't make any mistakes, this one keys to Ephemerella mucronata, which has not previously been reported any closer to here than Montana and Alberta. The main character seems to fit well: "Abdominal terga with prominent, paired, subparallel, spiculate ridges." Several illustrations or descriptions of this holarctic species from the US and Europe seem to match, including the body length, tarsal claws and denticles, labial palp, and gill shapes. These sources include including Richard Allen's original description of this species in North America under the now-defunct name E. moffatae in Allen RK (1977) and the figures in this description of the species in Italy.
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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Chris_3g has attached these 2 pictures. The message is below.
15" Brown - #16 Adams
16" - 17" (I'll call it a 16.5") Brown - #12 beadhead nymph (olive body, brown thorax)
Chris_3g
Posts: 59
Chris_3g on Jun 7, 2007June 7th, 2007, 4:31 pm EDT
Hey forum members. Thanks for all of the advice and posting and whatnot. It's definitely been a HUGE amount of help reading everyone's opinions.

I have a question though. These are the latest (and largest to date) fish that I've caught. They're both browns, but they're very different, and I just wanted to know why. Even the fight was different for each fish. The 15 incher seemed to want to pull really hard and then give up - this was repeated a few times. The 16.5 incher wanted to fight more consistently, harder, and longer. I assume this is normal, but was curious what you all had to say about it. Thanks!

Chris.
Troutnut
Troutnut's profile picture
Administrator
Bellevue, WA

Posts: 2758
Troutnut on Jun 7, 2007June 7th, 2007, 4:57 pm EDT
It looks like the 15 incher is a stocker and the 17 incher is wild, based on the coloration and the beat-up tail on the 15-incher. But I'm not an expert on telling the difference.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
CaseyP
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Arlington, VA/ Mercersburg, PA

Posts: 653
CaseyP on Jun 8, 2007June 8th, 2007, 3:11 am EDT
hey, great photos! posed the same question myself to a guide one day after spouse and i caught dissimilar wild trouts: "Fish are different for the same reason people are different." hardly scientific, but...
"You can observe a lot by watching." Yogi Berra
GONZO
Site Editor
"Bear Swamp," PA

Posts: 1681
GONZO on Jun 8, 2007June 8th, 2007, 4:25 am EDT
Chris,

The smaller brown appears to be recently stocked. The larger one is clearly in better color and condition, and is probably a holdover. Both fish seem to show the traits of a domestic brown trout strain. Although wild browns can display these same traits (especially if the wild population was derived from the same domestic strain), the eroded tail and wrinkled edge of the pectoral fin on the larger, cleaner brown suggest that it originated in a hatchery and has had time to color up and repair some fin damage. (The dorsal fin appears to be folded over, but I suspect that if it were unfolded, you'd also notice a kink in the leading edge about a third of the way up from the base.) Your account of the differences in their fight would reflect that as well. You didn't mention whether that water is known to have a wild population, but at least it appears suitable for allowing some of the stocked fish to survive and even thrive. Most of the difference between these fish can probably be attributed to length of time spent in the stream. If the smaller fish holds over, it will probably look very much like the bigger one in time.

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