While migratory fish depend on quality habitats to reproduce, many man-made features can inhibit their movement. There are currently over 250,000 barriers that can obstruct migration, with only a few being corrected each year. Fishwerks analyzes and optimally targets candidate barriers to maximize the return on investment from funded habitat improvement projects. 

The tool contains a map of the flowlines around the Great Lakes basin and classifies them according to how "passable" they are, where passable flowlines have few or no obstacles and impassable flowlines have many obstacles. The tool provides details on the obstacles obstructing the flowlines, such as type of structure, estimated cost for removal, and how passable the obstacle is in relation to swimming strength of certain species. Users can select scenarios by removing certain obstacles to see the long-terms costs of the project and the amount of habitat gained for certain fish species.