The cool, cloudy days of June bring the most epic mayfly fishing imaginable. Mayflies spend a majority of their life as nymphs, and begin to hatch in good numbers as the water temperature climbs up and over 60 degrees. Big rainbows will cruise the flats picking them off one by one, and can bring on some fast and furious action with both floating & sinking lines.
Knowing where to look in a mayfly hatch is half the battle. By far the best mayfly fishing will take place in fairly shallow water, usually in ten feet of water or less. When fish get keyed in on eating mayflies, they will cruise the flats foraging for them.
Mayfly nymphs can be easily fished under an indicator exactly how you would fish a chironomid pupa. Set your depth within a few feet of the bottom, make a cast and let it sit static until the indicator goes under. A very effective method for fishing mayflies under an indicator is casting perpendicular to the breeze and allowing your line to naturally dead drift at the speed of the wind.
This is hands down my favourite way to fish mayfly nymphs. My leader is made of 3 feet of 12lb fluorocarbon, to three feet of 10 pound fluorocarbon, down to my tippet that is generally 6lb test. Tapering your leader will make the sink rate a little bit more gradual, as opposed to naked line chironomid fishing where I will run a straight shot of 6 pound fluorocarbon. Make your cast slightly quartering downwind and allow it to sink for an appropriate time in relation to the depth of water you are fishing. If you feel the fly hanging up on bottom then lessen your countdown by at least 5 seconds. it’s good to be close to bottom but you never actually want your fly on the bottom of the lake. Once you start retrieving, keep it slow. I mean painfully slow, and very relaxed hand twist retrieve is all you need.
Intermediate sinking lines are very effective for fishing mayfly nymphs. Most fly line manufacturers make these lines, my favourite are the “hover” style lines that sink at 0.5-1″ per second which allows me to still fish very shallow water but without the wake that is created by a floating line. I rig a 9 foot leader off of these lines, built the same as I would for fishing a naked dry line.
Fishing mayfly nymphs right on the edges of a transition from deep to shallow water is very effective. Fish will often use these transitions to come up from the deep and feed for a short period of time before returning back to the depths. It’s very exciting watching a school of huge rainbows come up to cruise a shoal looking for food, but also demands flawless presentation to avoid spooking them. My favourite way to do it is actually anchoring and casting parallel with the ledge, positioning my fly line so it is right on the dropoff.