Announcing the DRA 2019 Macroinvertebrate Hatch Survey Report

The Deschutes River Alliance is pleased to present its 2019 Hatch Survey Report. As in previous years, this report describes survey data collected by lower Deschutes River fishing guides, documenting the presence and abundance of the major adult aquatic insect hatches on the lower river. The survey data compiled in the DRA Hatch Survey Reports represent a systematic attempt to document changes in adult insect emergence timing and abundance on the lower Deschutes River. The data, submitted by highly experienced guides and anglers, provides the only ongoing assessment of changes to the lower river’s aquatic insect populations.Here are some of the key takeaways from this year’s survey results and analysis:

• As in previous years, survey results show that adult abundance of the four major orders of aquatic insects—stoneflies, caddisflies, mayflies, and Diptera—is low from spring through fall. A majority of surveys reported “none” observed.
• Shifts in hatch timing were also observed, particularly for the pale morning dun mayfly, salmonfly, and golden stone. Salmonflies and golden stones have consistently emerged four to five weeks earlier than they did prior to the commencement of surface water withdrawal operations at Round Butte Dam.
• Adult hatches for the salmonfly and golden stone showed slight improvement compared to prior years. About 30% of surveys reported “high” abundance for salmonfly and golden stone in 2019 compared to 8% for salmonflies and 20% for golden stones in 2017.
• Hatches of Diptera (chironomids and crane flies) remain low. However, some recovery of the crane fly occurred, with 21% of surveys that reported low and moderate abundance and 1% reported high abundance in 2019.
• Changes in seasonal water temperature and annual water quality as a result of the Selective Water Withdrawal Tower have led to changes in the abundance and emergence timing of aquatic insects in the lower Deschutes River.

Despite all the challenges we are facing in this era of the Coronavirus epidemic, the DRA is continuing to advance our mission. Thank you to everyone who has reached out about the impact of the virus on your lives, families, communities and businesses. We continue to be grateful for your ongoing support of the DRA and the lower Deschutes River. Please stay safe during this time and we look forward to gathering with you again soon as we continue our fight to return clean, cooler water to the lower Deschutes River.