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.

View from atop the permafrost slump

From the Selawik River in Alaska

Stream photos

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Ephemerella mucronata Mayfly Nymph Ephemerella mucronata Mayfly Nymph

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.

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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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South Fork Castle Creek

Report at a Glance

General Region	Black Hills
Specific Location	Castle Creek near inlet of Deerfield Reservoir
Dates Fished	July 12-14, 2011
Time of Day	Afternoon
Fish Caught	Rainbows, Rock Bass, & 1 brook trout
Conditions & Hatches	Overcast. A few midges were hatching.

Details and Discussion

Bioprofsd

Mitchell, SD

Posts: 4

Bioprofsd on Jul 24, 2011July 24th, 2011, 5:22 pm EDT

I caught about 6 hatchery rainbows up to about 13 inches on olive wooly buggers near the footbridge over the inlet of Deerfield Reservoir in the Black Hills of South Dakota. The water was high and a little off-color, so I swithched to a prince nymph which has a little white on it and caught a wild brook trout and a wild rainbow (both small). Lots of rock bass in the lake and didn't have a boat, so I fished mainly above the reservoir in the creek. Sorry, no pictures.

Motrout