This summer the Huron River Watershed Council has been conducting a biological survey for freshwater mussels on the Huron River, below the Peninsular Paper Dam in Ypsilanti. We are about half done with this summer’s work.
A mussel survey is an important and mandatory part of taking out a dam. During dam removal, the fine sediment that has built up behind the dam is released and can harm downstream mussel populations.
Ultimately, the dam removal will be a good thing for the Huron River’s mussel population. Mussels do not move far in their lifetime, and they rely on fish to carry their larvae upstream. So, removing dams means these fish can swim further abroad, and spread new mussel populations throughout the river!
But on the short term, a dam removal can damage the biological community, so we are locating the mussels this summer, and next summer we will move many of them to a safer part of the Huron prior to the expected dam removal in late 2025.
Let’s walk through what a mussel survey looks like.
Setting Up the Transects
Every morning, HRWC mussel monitoring volunteers gather to learn from program staff what are doing, how we are doing it, and why. Melina Pakey-Rodriguez (HRWC’s Environmental Fellow), Alex Gonzalez (our lead summer intern), and myself are the primary drivers of the monitoring. But we have a great crew of enthusiastic mussel surveyors! Other HRWC staff, summer interns, students and professors from Eastern Michigan University, long-time HRWC volunteers, mussels experts from across Michigan, and local residents volunteering with HRWC for the first time all participate. And we couldn’t do it at all without the help and scientific expertise of Michigan mussel expert Dr. Renee Mulcrone.
Next, we get into the water. We stretch a transect (a measured rope) across the river. Each volunteer gets their own five meter section to search. Searching involves scouring the sediment by moving rocks and digging with a trowel to find the mussels. We spend a minimum of ten minutes doing this on each five meter section. Volunteers can go longer if they haven’t properly searched their section in ten minutes.
In really shallow water, it is easier to use a glass-bottom bucket than a mask and snorkel, as Ube demonstrates for us here.
Tallying Mussels
After searching for at least ten minutes, we tally the mussels to determine which of the five-meter sections had two or more mussels found. For those sections, we conduct more intensive quantitative samples. We randomly place three one-meter squares, made with PVC pipes, along the five-meter section. The mussel surveyor then has to search that square thoroughly to get every mussel from it. This takes a minimum of two minutes for each square but the person can go longer to fully search the area.
Throughout this whole process, mussel experts identify the mussels found and determine their sex and age.
Repeat!
When all of that surveying and recording is done, we pack up the gear and move the transect line upstream 25 meters, and repeat the process. And repeat, and repeat, and repeat. We need to do 90 transects in total in order to cover the full stretch of the Huron River that could be affected by the dam removal! It is a lot of work.
Mussel surveying is a fun and unique experience. We are excited to do it and excited to offer the opportunity to so many people to try their hand at it, too.
