Study Explores New Fish Passage Options for St. Croix Dams


In keeping with its role to monitor the health of the St. Croix river aquatic ecosystem, the International St. Croix River Watershed Board has released a study exploring opportunities and constraints for improved fish passage for the lower stretches of the St. Croix River.

A number of important fish species to the St. Croix River ecosystem, such as alewives, blueback herring, Atlantic salmon, American eel, sea lamprey, and American shad, once swam freely up the river to spawn before construction of dams in the 1800s. Fishways were built at these dams to help a limited number of fish to move beyond the dams to spawn and breed in order to maintain the species in the river. Existing fishways on the dams primarily pass alewives, with small numbers of shad and eels also making it upriver. As these fishways were built many years ago, the design and in some cases poor condition of the current fishways are a constraint to successful restoration of fish to the river. This fish passage concept study is a first and informational step to assist local stakeholders’ discussions on improving fish passage at Woodland and Grand Falls dams on the St. Croix River. The study considers a variety of factors ranging from geography, local geology, infrastructure, fish passage technologies, and the physical limits of several fish species. The study looks at opportunities for improving both upstream and downstream fish passage options.

Multiple concepts are assessed, addressing both up and downstream passage at each site, including new fish lifts, vertical slot fish ladders, modifications or expansions to existing fishways, and nature-like fishways. For example, a potential option for further exploration is a fish lift near the existing fishway on the Woodland dam to help species move upstream, with modifications to the existing intake bar rack or a new, larger one to help fish move back downstream safely. Options at the Grand Falls site include passage at two locations, the powerhouse (location of the current Denil fishway) and at the dam. A vertical slot fish ladder is an option for consideration at Grand Falls along the right dam abutment with a number of different options such as including a surface bypass weir on the spillway and gate modifications to help fish move back downriver. The study also identified data gaps and additional studies that will be needed to inform analysis of these concepts.

The study is being provided to stakeholders in the watershed to assist with local efforts to improve fish passage on the river. The International St. Croix River Watershed Board worked with multiple stakeholders and public and private interests including Woodland Pulp, US Fish and Wildlife Service, US Geological Survey, Maine Department of Marine Resources, the US National Oceanic and Atmospheric Administration, and the Department of Fisheries and Oceans Canada, as well as local first nations communities including the Peskotomuhkati Nation and Passamaquoddy Tribe, on the concept study. The IJC is grateful for the interest and participation of many local partners in this study. The study is a project of the IJC’s International Watersheds Initiative.


For more information, contact:

Kevin Bunch, US Section Office                              202-632-2014 

Sarah Lobrichon, Canada Section Office                613-992-5368