Hendrickson mayfly hatch ( Ephemerella subvaria ) is is a prolific mayfly hatch on many northern Wisconsin freestone streams. The abundant Hendrickson nymphs are found crawling on the gravel bottoms in the riffle sections of the streams. Depending on the Spring weather and stream conditions, Hendrickson nymphs can be emerging any time from mid-April to mid-May. If the air temperatures stay cooler the Hendrickson hatch can last for 2 to 3 weeks, offering fly fishermen some great Spring dry fly fishing.
During the morning hours trout will begin to key in on the Hendrickson nymphs. Ephemerella subvaria nymphs become very active prior to emerging and the nymph's wing cases will turn very dark. A size #12 hare's ear nymph can be deadly before the hatch starts. Once the Hendrickson hatch begins a CDC wing emerger or a soft hackle-wet fly can be deadly. When Hendrickson duns start to appear on the surface a size #12 or #14 Hendrickson comparadun, or Sparkle Dun patterns can make an exciting afternoon of dry fly fishing for rising trout.
The male Hendrickson duns are generally smaller than the females, including larger eyes and a dark reddish abdomen color. The classic male Hendrickson dun pattern is the Red Quill. The female Hendrickson duns (Classic Light Hendrickson pattern) are more of a gray-brown color with a touch of pink and have smaller eyes. This can be important to take notice of because at times feeding trout may become very selective for either the male or female emerging duns. Hendrickson duns have three tails.
In cooler Spring weather the Hendrickson hatch will begin around 1:00-2:00 pm and can last for a couple of hours. On overcast days the hatch may sporadically occur from late morning through the afternoon, depending on temperatures. If the weather is unseasonably cold the duns may be forced to ride on the surface for a long time before being able to fly off, which makes the helpless Hendrickson duns an easy meal for rising trout.
During Spring evenings don't pass up the terrific Hendrickson spinner falls. The spinner falls generally occur around dusk over the stream riffles and faster water sections of the river. Hendrickson spinner falls may also appear in the morning during unusually warm Springtime temperatures. A Rusty Spinner pattern in sizes #12 or #14 is the best choice for the Hendrickson spinner falls.
Click here for Hendrickson mayfly patterns.