(Stonefly exoskeleton, photographed in 2018 by Dennis Hinton)

By Judy Pickens
Special to West Seattle Blog

Did aquatic insects living in lower Fauntleroy Creek benefit from the 244 spawner carcasses that have been decaying since November? You bet, according to student researchers from Louisa Boren STEM K-8.

A dozen fourth graders, led by volunteer educator Shannon Ninburg, conducted the Fauntleroy Watershed Council‘s annual early-spring count of stonefly exoskeletons on Sunday, March 27, and found the third-highest number in the study’s 22-year history.

Stoneflies live in freshwater up to three years, then crawl out to shed their exoskeletons, fly, and mate to start the cycle of life over again. Stonefly nymphs are a significant food source for juvenile salmon, plus they are an indicator of water quality as they cannot tolerate high pollution.

(Sunday video by Tom Trulin)
Teams of students counted all the exoskeletons they could find in the study area, looking on trees, bushes, fences, and bridges near the water. One team focused on measuring torsos.

They found 62 exoskeletons – the most in three years. Average size of 10 specimens was 4 cm; one measuring 6 cm was among the largest ever recorded over the years.

After reviewing their data, the students reached conclusions about why the number of exoskeletons was so high this year and why most stoneflies exited the creek where they did. After students approve the final report, the watershed council will share it with regional salmon-habitat specialists and post it at fauntleroywatershed.org.