Updated: May 11, 2020
The 'Small Dark Olive', Baetis Scambus marks for me the start of the season in the rivers of mid-Sweden. When going to my home river during the premiere I know that this fly is the one I need, I estimate the ratio of Baetis Scambus vs Baetis Rhodani in my river to be around 9:1. It's strange though because even if I know this is the first ones to hatch it's always the last flies that leave my vice before season opening, what's up with that?? However, this mayfly belongs to the Baetidae family and is one of the first to hatch alongside Baetis Rhodani and Baetis Niger. They live in running rivers, both slow flowing and fast flowing. The size of this mayfly in the adult stage (imago) range from 5-11 mm. During the early season they tend to be a bit bigger compared to later on. For the early season I fish them on mainly hook size 18, maybe 20 and then going down to 20-22 during the fall season when the second hatch occurs.
The Baetis likes shitty weather. When the clouds are hanging low and there's a fine pouring rain, good water temperature (preferably above 9-11 degrees) and high humidity you know you can expect a good hatch. Sometimes they come in crazy numbers and while the fish start to rise it can also make you crazy, 'cause the fish won't take your fly alongside the mat of the real Baetis or perhaps I'm just a bad fisherman. What do I know?
The characteristics of this mayfly is its smokey grey wing, brownish olive greyish body, their small hind wings and two tails. Trying to distinguish the Baetis species is almost impossible, but following the information here and the time (May/June and September/October) is right you can expect it to be a Baetis. In my opinion they tend to be a bit lighter during early season whilst darker during the late season.
A deer hair comparadun of a Baetis, size 18.
Baetis has become my favorite fly. I don't know, maybe it's because this mayfly hatches throughout all season long and is a staple in my boxes. Or maybe it's because it's intriguing to attract the biggest trouts with the smallest of flies. When fishing these hatches I tend to fish flies that are slender bodies and thin-dressed, too often I see variations of this fly being to bulky. I fish them in both grey, olive, dark olive and brown olive colors and I almost always use a smokey grey wing (I don't know if that matters but it makes me confident). Favorite patterns include the standard parachute, The Last Chance Cripple by Rene Harrop, Barr's Emerger, standard spent, and Craig Matthews Sparkle Dun. For picky trout I like to use a comparadun. AND do not forget to downsize the tippet to get these small flies to behave naturally in the water.
Tie some flies or order in the shop, get out there and have a good time. Don't forget the coffee. 'Til next time.