Trout Unlimited is doing a citizen science project in our area: Environmental DNA sampling to locate hidden brook trout populations in the NYC suburbs: Fairfield, Westchester, Putnam, and Long Island.
Their plan is to cover 400 miles of streams, starting with locations where there was historic Brook Trout presence, but no recent state sampling. Then expand to include other streams to find previously unknown populations. This will help guide TU in restoring and protecting the habitat for these native salmonids.
Gerald Berrafati of the Mianus chapter is leading the effort. I met him out fishing the Amawalk last spring, so I decided to go out to his presentation at the Mianus chapter’s meeting to learn more. (I’m a part of the Croton chapter next door.)
They’ve already taken 130 samples and confirmed brook trout populations in 21 streams, with early signs that number could be as high as 40, including an unknown salter spawning population on Long Island. That is incredible in such a densely developed region.
The way eDNA testing works:
- Collect a water sample
- Filter it to capture organic material
- Extract and amplify DNA via PCR
- Match against reference databases to identify species
- Tag the results with GPS coordinates and add to a database
You can learn more about it here:
The testing is so sensitive that it can detect fish a mile or two upstream of the sampling location. That is pretty wild. It only can tell you absence/presence though, nothing about the size of the actual population. It needs to be followed up with stream assessments, electro-fishing, and spawning surveys.
Another citizen science tool TU has is the RIVERS app, where folks can submit on-the-ground information about a stream while they are out fishing. A geotagged photo of a brook trout is a great way to confirm presence. You can also tag old dams, erosion sites, etc. I downloaded it and will use it this season.
I signed up to help in Westchester and Putnam. I’ve asked other fly fishers where they’ve caught brook trout in the the area and have some ideas of places to check out. Charlie and I will go out on some hikes to take water samples in the spring once things thaw out. I need to get him some waders!
TU gets their eDNA testing kits from Jonah Ventures. I’m going to buy one separately to sample Dickey Brook in Blue Mountain Reservation near our house. It primarily runs through protected land, has decent flows year-round, and has some macroinvertebrate life. I want to know what else is in there!
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