By: Kate Miller, PhD — Middlesex Land Trust Board Member
Later this year, the Highland Pond Dam, located on Middlesex Land Trust (MxLT) property along Sawmill Brook in Middletown, will be removed to reinstate connectivity within the stream. That’s important for fish communities and the watershed’s ecology. Dam removal can be messy business: sediment that has accumulated over decades may move downstream, and stream flow may be altered, which could impact the banks and streambed. Post-removal, it may be helpful to assess the stream to ensure any necessary steps are taken to restore or enhance quality. It’s best practice to be able to compare the post-removal state of the stream to pre-removal conditions to see what has changed.
To that end, and in order to learn about various field assessment techniques, Wesleyan students of a new community-engagement course, Strategies in Conservation and Environmental Action, conducted field work along the stream below the dam last fall (September, 2024). They gathered data on three aspects of the stream: physical habitat (e.g., streambed, banks, and water quality), and fish and benthic macroinvertebrate communities. The students reported and explained their observations in a report that was delivered to the Land Trust at the December board meeting by board member and course instructor, Kate Miller, along with Leo Heller, one of the students.
Habitat observations were done with a guide provided by the CT River Coastal Conservation District (CRCCD). Sampling of the fish community was done via electrofishing with Dr. Barry Chernoff, Director of the Bailey College of the Environment at Wesleyan University. Invertebrate sampling was done following a modified protocol from CT DEEP’s rapid bioassessment for volunteers. CRCCD staff were on hand for habitat and invertebrate sampling to help guide students.
Results show a stream that has plenty of riffles and pools to support biodiversity, a vegetated buffer to protect it from many anthropogenic impacts, a fish community that is fairly healthy, supporting a decent diversity of fish species (dominated by black-nosed dace), and a good variety of benthic macroinvertebrate organisms. These animals, which include mostly insect larvae like caddisflies, mayflies and other types of flies, are good indicators of habitat and water quality since the “tolerance” to degraded systems is well known for each species collected. They’re better indicators than random water chemistry tests, which are expensive and only reflect a snapshot of time. Results of invertebrate sampling show that the stream is not significantly degraded, but is not yet “healthy.” It’s somewhere in-between, and time will tell if dam removal will impact that or if the problem lies further upstream.
It’s worth noting that the sampling was conducted while we were in a prolonged drought, which might have artificially increased the number of fish and reduced the number of invertebrate species collected.
While this wasn’t the students’ primary project for the semester, they reported that they got a lot out of the experience, learning field techniques, collectively creating a document for the land trust, getting to interact with various experts, and spending an afternoon at this beautiful spot.
For more information, contact Jeb Stevens, MxLT Executive Director.
