BWO Hatch


The BWO hatch on the lower river last week was something I was looking forward to. I have been in Montana a few months now and as spring arrives with warmer temps, I’ve had some fantastic dry fly midge fishing and now mayflies. Friends have had great Skwala fishing on the Bitterroot and I had a lovely rainbow eat one yesterday on the Gallatin! Fishing the hatches in the US is something I had read about and now I am experiencing it first hand!

My previous experiences with hatching mayflies have mainly been in the Mataura river, Southland NZ or on the Tongariro river Central North Island. The larger mayflies in the North Island were the Colobriscus – imitated nicely by the “Khakahi queen” size 12 and 14 and those in the south were Delatedium – nicely matched by the “Dad’s favourite” 16 and 18s (one of the more endearing names for a fly!) Now in Montana I am busy reading hatch charts and learning new flies, patterns and waterways.


In contrast to NZ we would look forward to bright sunny days to take advantage of the predominately sight fishing opportunities . Low light and overhead cloud were great for hatches on the Mataura in April but then fish spotting became more challenging. Compare this to the conditions I have learnt to favour in my local rivers around Bozeman. Overhead cloudy days, perhaps with rain or even snow, early in the season, support the heaviest hatches.

As a lot of the fishing is blind or to risers 45 North, I have found the ability to read water and find prime feeding lies a real asset. Fish numbers are much greater than I have experienced in NZ (The Madison, boast counts in the thousands of fish per kilometre! ) but they are not dispersed everywhere. The fish may pod up for security when feeding and also the hatch itself may be very localised. Knowing where to look for feed lanes and finding fish is a skill. Particularly on the “100 mile riffle” - the Madison.

This week I fished the lower Madison. The wind was light where I was and the pewter sky was everything I had read was conducive to encouraging a good hatch. As Light snow fell throughout the day I experienced an incredible hatch of small BWOs. In fact I “left them rising” feeling replete as I had had more than several hours of wonderful dry fly fishing.

Wading quietly I would approach each rising fish to within 20-30 feet. Keeping casts short and my leader long (12-15ft) I could present my fly accurately. I may have had to present multiple times if necessary so the fish could see my fly amongst the dozens of naturals that were floating overhead at any one time. Several times I “upsized”my pattern just to stand out from the crowd! Using this strategy I coaxed a good number to my dries and was pleased with the confident way in which the fish took my freshly tied imitations.

In contrast to NZ the flies I used were generally smaller to match the hatching mayflies. I used a range of imitations from parachutes and sparkle duns to cdc emergers - varying things up depending on the surface water conditions and my ability to see my fly amongst all the tiny sailboats coming downstream. I was using 16s and 18s as opposed to my default 14 on the Mataura.

Upon comparing my flies and the naturals, even a 20 might have been a better size match but those hooks seem to small for me just yet!

I rarely use full hackled traditonal patterns anymore although have fun tying them. Fishing flies that can double as emergers or duns works best for me. The quigley cripple style and sparkle duns work very well. Ive attached a few photos below and am tying in preparation for the next good overcast day. I’m also beginning to research the next major hatch we will see on the local rivers here. The Mothers day caddis!

BWO sparkle dun

BWO sparkle dun

BWO cripple

BWO cripple