Abundant and Stable Rocks Are Critical Egg-laying Habitat for Insects in Restored Streams

by Michelle Jewell, NC State University

M.Sc. student and author, Samantha Jordt, recording insect egg presence in a stream. Courtesy of NC State University.

The abundance and other characteristics of rocks partially extending above the water surface could be important for improving the recovery of aquatic insect populations in restored streams.

Nearly three quarters of stream insects reproduce on large rocks that sit above the water surface by crawling underneath to attach their eggs. Increasing the number of large and stable emergent rocks in streams could provide more egg-laying habitat and allow insects to quickly repopulate restored streams.

“We found that restored streams had fewer emergent rocks for egg-laying and fewer total eggs than naturally intact streams,” says Samantha Jordt, first author of the paper and an M.Sc. student at NC State’s Department of Applied Ecology.  

The study also found that some of the large rocks in restored streams were unstable and rolled or were buried by sediment between Samantha’s visits. According to the study, these variables combined–fewer large rocks available for egg laying and that some of those rocks were unstable–may delay insect recovery.

Read more here: https://news.ncsu.edu/2021/03/insects-in-restored-streams/

Read the Ecology paper: https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/ecy.3331