The Yakima River BWO

The hatch of these small mayflies will occur on virtually all western trout streams and are an important food item for the Yakima River trout.  The Blue Wing Olive (B.W.O.). begins its emergence cycle typically during the month of February or early March and will continue well through the month of May on portions of the Upper Yakima River in Kittitas County.

These important little food items will make their return once again in the fall months of September, October and November and can even be seen at times throughout the winter months of December and January.

The hatch usually will begin around 11:00 a.m. and can last well into dusk, depending on the time of year it happens to be.  The best emergence and trout feeding opportunities will occur during the cloudy days of spring and late fall.

The life cycle of this little mayfly is quite extraordinary.  One generation hatches in the spring and lays its eggs into the water.  The nymphs grow feeding on algae and vegetation and emerge once again in the fall, starting the cycle over again before winter. 

The Yakima river's fall emergence of Baetis, tends to be quite smaller in size compared to the spring emergence with sizes ranging in from #16-22.  In spring, you will find sizes ranging from #14-18.

Because the nymphs are tiny they have trouble breaking the surface of the water.  Once the hatch begins the duns fly to the bank where they remain until there metamorphosis to the spinner stage.  You will see the spinners in the late afternoon or evening depositing there eggs on the surface on the water.

The No HackleBlue Wing Olives are a three-tailed mayfly with a brownish-olive body and light dun wings, hence the name Blue Wing Olive.

Every fly-fishermen should be prepared for this hatch and carry the patterns that best match the natural.  Here on the Yakima, we like to use the No Hackle to imitate the spring and fall emergence of Baetis.


Family Genus Body Color Wing Color Emergence

Blue Wing Olive Baetidae Baetis Dark Olive Dun Morning/Evening

Home | Contact Us | River Reports | Fly Fishing Adventures