This year’s Stonefly Search was a great success, with 145 volunteers (!) coming out on a Saturday to hunt for stoneflies in streams across the watershed. The winter weather was kind, with mild temperatures and some fluffy snow that started to fall in the afternoon. Everything got a little damp, but collectors stayed in good spirits!
Stoneflies are a group of aquatic insects that are highly sensitive to pollutants in our waterways, so finding stoneflies is an indication of healthy water quality in our rivers and streams. The more we find, the better! HRWC has been monitoring stoneflies in our creeksheds for many years, and we use the data to track changes in stonefly populations and water quality over time. You can find a summary of our data here.
At each of the sites that we monitor, volunteers collect all of the different types (or families) of stoneflies that they can find and rate the total abundance of all of the stoneflies observed. During our winter stonefly searches, we typically find that most of our sites remain stable, with some sites exhibiting changes in the relative abundance of stoneflies and number of families found. Some yearly variability is expected, but a continual decline in stoneflies at a particular site is a red flag, possibly indicating a drop in water quality.
Highlights from 2020:
This year we investigated whether the diversity of stonefly families has increased or decreased in recent years by comparing the average number of stonefly families found in our last three years of sampling to the average number of families found across all our sampling years. Of the sites sampled in 2020, there were more families found on average in recent years at 4 of our sites, but there were fewer families found at 10 sites.
Among the sites that exhibited a drop in the average count of stonefly families is Arms Creek at Walsh Road. Two families, Capniidae and Taenipoterygidae, were consistently found here in the past, however no Taeniops have been found in the last three years of sampling. Capnids were found this year, but they were rare. We’ll have to keep an eye on Arms Creek to see if this trend continues over time. At Hay Creek at M-36, three families have been found consistently in the past, however this year was the first time that no stoneflies were found. This could be due to annual variability, but we will also continue to watch Hay Creek for any declines in water quality.
There is good news! Honey Creek has exhibited declines in the aquatic insect community over the years, however it looks like the stonefly population in certain sections of the creek may be improving. In Honey Creek at Jackson Road, stoneflies had not been found since 2008, but volunteers found them once again in 2017, 2018, 2019 and 2020. Stonefly abundance appears to be increasing over time as well; this year volunteers reported that Capnids were found frequently, which is similar to reports from pre-2008 sampling events. Stoneflies have also been found again in Honey Creek at Wagner Road in both 2018 and 2020, although so far, they remain rare. We will continue to monitor Honey Creek to see if improvements in stonefly counts continue over time.
On a final note, this was the first year that the family Perlodidae was found at Mill Creek at Manchester Road – exciting for the creek, and for me! ~ Perlodids are fun to identify. See a photo of a Perlodid through a microscope viewfinder above.
Stay in touch with HRWC to volunteer for future insect searches! Our volunteer programs are temporarily suspended due to COVID-19 precautions – but if you’re interested in volunteering with HRWC in the future, please sign up here! We will get in touch with you when our regular programming resumes.
Summary of the 2020 sites that displayed a change in the average number of stonefly families found in recent years:
| Sites that improved |
|---|
| Fleming Creek at Galpin Road – Washtenaw County |
| Honey Creek at Darwin Road – Livingston County |
| Honey Creek at Jackson Road – Washtenaw County |
| Woods Creek at Lake Huron Metropark – Wayne County |
| Sites that declined |
|---|
| Arms Creek at Walsh Road – Washtenaw County |
| Boyden Creek at Delhi Road – Washtenaw County |
| Hay Creek at M-36 – Livingston County |
| Hummocky Lick at M-36 – Livingston County |
| Huron River at Commerce Road – Oakland County |
| Huron River at Island Park – Washtenaw County |
| Mill Creek at Fletcher Road – Washtenaw County |
| South Ore Creek at Bauer Road – Livingston County |
| Boyden Creek at the Golf Course – Washtenaw County |
| Sites that remained stable |
|---|
| Davis Creek at Doane Road – Livingston County |
| Davis Creek at Pontiac Trail – Oakland County |
| Davis Creek at Silver Lake Road – Livingston County |
| Fleming Creek at the Botanical Gardens – Washtenaw County |
| Fleming Creek at Geddes Road – Washtenaw County |
| Fleming Creek at Warren Road – Washtenaw County |
| Honey Creek at Wagner Road – Washtenaw County |
| Horseshoe Creek at Merrill Road – Livingston County |
| Huron Creek at Dexter-Pickney Road – Washtenaw County |
| Mann Creek at VanAmberg Road – Livingston County |
| Mill Creek at Ivey Road – Washtenaw County |
| Mill Creek at Jackson Road – Washtenaw County |
| Mill Creek at M-52 – Washtenaw County |
| Mill Creek at Manchester Road – Washtenaw County |
| Mill Creek at Shield Road – Washtenaw County |
| Mill Creek at Mill Creek Park – Washtenaw County |
| Portage Creek at Dexter-Townhall Road – Livingston County |
| South Ore Creek at Hamburg Road – Livingston County |
| Traver Creek at Broadway – Washtenaw County |
| Woodruff Creek at Buno Road – Livingston County |
| Traver Creek at Dhu Varren Road – Washtenaw County |
| Traver Creek at Traver Road – Washtenaw County |
| Sites where we have never found stoneflies |
|---|
| Greenock Creek at Rushton Road – Livingston County |
| Horseshoe Creek at Brookside Drive – Washtenaw County |
| Mallets Creek at Chalmers Road – Washtenaw County |
| Millers Creek at Glazier Way – Washtenaw County |
| Portage Creek at Unadilla – Livingston County |
| Walker Creek at 8 Mile Road – Livingston County |