October 6, 2015 — The following was released by NOAA Fisheries:
By Sean McDermott, Greater Atlantic Region, Habitat Conservation Division
Have you ever seen a fish ladder or a fish lift? Do you know how one works? For many people the answer to both is “no.” If you live along the coast or on a river, there may even be a fish ladder or lift near you. Why do fish need these devices?
Migratory fish such as sea lamprey, rainbow smelt, American shad, alewife and blueback herring live and grow in the ocean and return to rivers to spawn. They arrive in coastal rivers every spring, with some rivers seeing millions of fish. After spawning, they return to the sea. Then, in the fall, millions of young fish make their way from river to sea. These fish become prey, or bait fish, supporting popular commercial and recreational fisheries. Stripers, Atlantic cod, and bluefish, to name a few, rely on these migratory fish for food. In addition, marine mammals also prey on these fish.
Fish Versus Dams: A Centuries-Old Battle
Harvest of sea-run migratory fish once provided an important food source for Native Americans and colonial settlers. Rivers also provided travel routes, and hydro-mechanical power for development of agricultural and industrial technology. As technology developed, the construction of dams for navigation and hydro-mechanical power spread, blocking the migration of those sea-run fish. The conflict between dam-building industrialists and commercial fishers led to the “Shad Wars” from 1780 to the late 1800s, with warring parties shooting guns and cannons at each other and destroying weirs and dams, all in the pursuit of the best fishing spots.
In the end, dams rose and migratory fish populations fell, taking with them the economic and cultural traditions they once supported. Populations of several species are now at all-time lows. Three species (Atlantic salmon, Atlantic sturgeon, and shortnose sturgeon) are listed under the Endangered Species Act, and four others (rainbow smelt, alewife, blueback herring, and American eel) are either species of concern or have been petitioned for listing under the Act.
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Read more stories from our Habitat Conservation Division.
Questions? Contact Jennifer Goebel, Regional Office, at 978-281-6175 or Jennifer.Goebel@noaa.gov.
An Alaskan steeppass is typically designed for small dams. The ability to reduce energy within the chute allows the steeppass to be built at a higher angle. Photo credit: Sean McDermott, NOAA.