Removing Barriers to Migratory Fish
- By Kathy Reshetiloff, Bay Journal
These photos show Clifford Branch in Frederick County, MD, before and after a culvert was removed in 2017. A dam, 2 miles downstream, was removed in 2012. The two projects will allow brook trout and other native fish passage on the waterway. (Mark Secrist / U.S. Fish and Wildlife Service)
Warmer, longer days, spring flowers and the chorus of frogs and songbirds lure me outside to get moving. And for fish it is no different. Early spring is when many fish species are on the move, migrating to other areas to spawn.
The Chesapeake Bay watershed, a kind of watery interstate, is a vital corridor for migrating fish. Resident fish, like yellow perch, move up and down the same river. Anadromous fish journey from oceans to freshwater rivers and creeks to reproduce. Anadromous fish known for their spring spawning runs include blueback herring, alewife, hickory shad and American shad. Conversely, catadromous fish, like American eels, swim downstream from freshwater to saltwater to spawn.
In the last 200 years, though, populations of these species have decreased drastically. Other river species are in decline as well. For example, freshwater mussels, which require a host fish to complete their life cycle, are imperiled throughout their range.
One important factor in these declines is due to dams, undersize culverts and other barriers that prevent fish, mussels and other aquatic wildlife from moving to areas to complete their life cycle.
This eelway, installed in 2019, will help immature American eels get past Dam #5 near Falling Waters, WV, on the Potomac River. (David Sutherland / U.S. Fish and Wildlife Service)
These barriers also impede natural river flows and function. Sediments, once carried by rivers to coastal wetlands, are trapped in reservoirs and pools above dammed rivers. The trapped sediments no longer replenish coastal marshes, which adversely affects seafood nurseries and bird habitats along shores and estuaries.
Free-flowing rivers are crucial to sustaining healthy fish populations. And, they enable mussels, reptiles and amphibians to reach important breeding, wintering and feeding habitats. Free-flowing rivers sustain important natural processes such as cycling nutrients, distributing sediments and maintaining appropriate water temperature and oxygen levels.