Each spring, as birds take to the sky and head north, bringing bright colors and cheerful songs with them, an equally massive migration is taking place just beneath the surface of our inland waters.
In the eight states and two provinces surrounding the five Great Lakes, many of these migrations are of fish heading from their large lake homes up into small tributaries to find a suitable place to lay eggs. This may take the form of a large northern pike worming its way upstream in a small agricultural drainage ditch. Or a steelhead flashing in a riffle. Or, as Center for Limnology graduate student, John Rodstrom, recently observed – white suckers stacked up against the current of an impassable road culvert.
As you’ve likely already read (or watched) on this blog, Rodstrom is out in the field looking at places where roads, dams and train tracks cross the hundreds of creeks, streams and rivers that flow into our Great Lakes. The McIntyre lab here at the CFL has produced an amazing online mapping tool of all such locations and its up to students like John to get out in the field and identify which ones are actually preventing fish from moving to upstream habitat. Knowing this could better help us in efforts to conserve fish populations and help them reach more and better spawning grounds.
This month, John is working in streams up in Door County and sent a video back from one particular road crossing where the high rate of flow at a road culvert was preventing upstream passage – you can watch this solitary sucker try, and fail, to get where it’s going below.
Oftentimes when John reaches such an impassable spot in a stream, fish are stacked up fin-to-fin and gill-to-gill as they try to navigate the barrier. This year, though, our unusually warm winter and early spring thaw sent fish on their journey early and John likely caught the (no pun intended) tail end of the migration. Below is a shot of the same culvert last year.
As you can see, the stream was no more passable, but a whole lot more fish were following their instinct to head to upper reaches to spawn. We’ll keep you posted as spring migration continues and will keep working to better understand how human activity and ecosystem functions intersect and how we can help get fish moving again. Happy Fish Fry Day!