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For Atlantic salmon biologists, field season kicks off in late April and early May with the deployment of smolt wheels—big rotating drums that sit in the river’s current and collect out-migrating salmon smolt (juveniles making the transition from fresh to saltwater).
Smolt typically travel downstream at night, in the river’s main current, and near the surface of the water column. Smolt wheels, also known as ‘rotary screw traps,’ are uniquely designed to safely capture migrating salmon at this special life stage. Trapped smolt are weighed, measured, and sometimes fitted with a Passive Integrated Transponder, or PIT tag, a magnetic device that quickly identifies the fish when it is scanned. Tagged fish are released upstream, and the number of smolt captured a second time can give an estimate of the run count as well as the efficiency of the smolt wheel.
Knowing how many smolt a river produces helps paint a picture of its overall productivity. A healthy ecosystem produces a healthy smolt run. ASF and its partners have maintained decades-long datasets on several Canadian salmon rivers, like the Miramichi and Grande Cascapédia.
This spring, two smolt wheels were set up in totally new rivers. ASF brought smolt wheels out of retirement and deployed them on the Nepisiquit and Terra Nova Rivers (WSW pilot watersheds). It’s the first time a smolt has been installed on each of these rivers—and in the case of the Terra Nova, the first time one has been installed on the island of Newfoundland.
For each installation, ASF staff were on hand to provide knowledge and direction. In the Nepisiquit, staff and volunteers from Pabineau First Nation as well as the Nepisiquit Salmon Association worked under the guidance of ASF Senior Scientist Jon Carr. Meanwhile, Wild Salmon Watersheds Program Director Kris Hunter and Science Coordinator Jordan Condon travelled to Newfoundland to help there. They worked alongside the Freshwater Alexander Bays Ecosystem Corporation (FABEC) to install the Terra Nova screw trap.
Of course, getting the smolt wheel in the water is just the first step. It needs to be tended regularly, and if there are fish in the live trap they need to be counted, measured, and tagged.
A core element of the Wild Salmon Watersheds program is long-term monitoring; when we know how many smolt a river produces and how many adult salmon return, we can target our conservation work.
ASF’s Wild Salmon Watersheds program is all about resiliency. It’s about protecting watersheds that are currently healthy, so they can support vibrant salmon populations long into the future. As Vice-President of Regional Programs Nathan Wilbur puts it: “when a drop of water falls in the forest, and it hits a healthy forest and it percolates down through the ground and into the soil and eventually makes its way into the river, it’s cold, it’s clean. That sets the stage for a healthy ecosystem, and in a healthy ecosystem you have healthy wild Atlantic salmon.”
With the critical data from new smolt wheels on the Nepisiguit and Terra Nova, ASF and its partners are well on their way to targeted, meaningful, long-term protection of these important salmon ecosystems.
