Connecticut River Coordinator's Office
Northeast Region
Photo of the Mary Steube fishway in Old Lyme, CT, built to pass herring above this small mill dam - Photo credit:  U.S. Fish and Wildlife Service
Photo of the Mary Steube fishway in Old Lyme, CT, built to pass herring above this small mill dam. Credit: USFWS

Since dams destroy and degrade stream habitat, and obstruct fish access to important habitat, solutions are needed.

Restoring Habitat

Dam Removal

  • Dam owners

    Dam owners have the responsibility of maintaining the safety of the dam. Consequently, old infrastructures may need to be removed or repaired at considerable cost.

  • Cost

    Cost of removing a dam is variable. Removal depends on height, length, location, and upstream sediment contamination. Most dams are removed in careful stages to avoid the release of accumulated debris downstream and to prevent erosion. Generally, removing a dam costs less than repairing one.

  • Assistance

    Removing a dam is a process involving the owner, the town, and others. Refer to the sites below on a step-by-step dam removal process, and for potential sources.

  • Benefits

    Dam removal is the only way to restore habitat. It opens miles of river for migration, spawning, and juvenile nursery habitat.

Workers remove the Winchester Dam from the Ashuelot River in Hinsdale, NH
Workers remove the Winchester Dam from the Ashuelot River in Hinsdale, NH. Credit: USFWS

Improving the Conditions of the River

Changing the Operation of the Dam

By changing the operation of a dam, obstacles to fish passage can be minimized and aquatic habitat can be improved. Some ways dam owners and power producers change the operation of a dam include:

  • Spilling water over dams at critical times like during migration seasons

  • Installing screens or other structures to allow fish to bypass turbines

  • Lowering water behind the dam to provide run-of-river flow in non-flood periods

  • Refraining from producing power during periods of migrations

Providing Access to Habitat

Building a Fishway

Dam owners can construct fishways to pass fish above and below their dam. Fishways do not restore habitat. They allow dams to remain intact, while enabling fish migration. Different species of fish prefer different types of fishways depending on swimming ability.

The solutions for habitat problems caused by dams include dam removal, changes in dam management and operations, and fishway construction.

How to Get Migratory Fish Around a Dam

There are more than 1,000 dams in the Connecticut River watershed. Dams can interrupt water flows, warm the water, block the natural movements of fish, and concentrate predators.

Fish ladders help to restore rivers. Successful fish passage projects have been initiated by individuals and organizations.

You can help! The following steps provide a general outline of how to get started.

  1. Work with agencies to choose a dam where fish passage is needed .

  2. Identify the dam owner by contacting the state dam safety office, the assessors office, or the registry of deeds.

  3. Contact the owner to determine their willingness to allow fish passage at their dam.

  4. Take photographs of the dam and the stream above and below the dam.

  5. Develop partnerships with environmental organizations, community groups, businesses, etc. This will help to get funding as well as distribute the work load.

  6. Once these steps are underway, you'll be ready to develop plans, get funding, and ultimately, build the fishway!

Why stock salmon above dams?

Young salmon are stocked above dams because that's where their habitat is. To survive and grow, salmon need specific habitat: cold, fast streams. There are now over 1,000 dams in the Connecticut River basin. Nearly all available salmon habitat is above at least one of these dams.

While the dams pose a number of problems for both adult and juvenile salmon, they have not made it impossible to restore salmon.

Dams can prevent returning adults from reaching their natal stream to spawn. While wild spawning is a long-term goal of the program, for now most wild salmon are trapped and manually spawned at hatcheries, before they reach their spawning grounds. This ensures successful reproduction, and benefits the entire program. When there are enough adults waiting at the base of a dam, that helps to justify upstream passage.

Dams make it difficult for young salmon to reach the ocean. The ponded area above dams can delay fish and warm the water. At some dams, fish can spill over the top without much harm. However, other dams have spinning turbines that can kill the fish.

Many dam owners have worked with agencies to develop ways to successfully pass fish. Downstream passage strategies include lights, diversion structures, and stopping turbines during peak migration. Upstream passage facilities include fish ladders and lifts.

Despite the dams, Atlantic salmon stocking has resulted in over 4,000 adult returns to the Connecticut River to date, with many more on the way.


Last updated: September 8, 2010
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