Human-made barriers prevent fish from accessing habitat needed for all stages of their life cycle. Fish need to access different types of habitat across seasons and life stages, and they need connected waterways to thrive. Migratory fish, including those that migrate between oceans and freshwaters (diadromous fish) and those that migrate within freshwaters (potamodromous fish), are particularly dependent on the ability to move freely through our rivers, streams and lakes.
Some of the best known examples of migratory fish include salmon, which spawn in freshwater and grow in the ocean; American Eel, which spawn in the ocean and migrate to brackish and freshwater systems to grow; and and Sturgeon, which can migrate hundreds of kilometers up rivers from lakes and estuaries to spawn. Lesser known examples include many sucker species, which migrate up small streams to spawn and are important prey for popular sport fish, and Northern Pike, which make shorter migrations into wetlands and flooded areas during spawning season.
Often when we think of barriers, we think of large hydroelectric dams, some of which have ladders designed for one or a few species to pass. But many other barriers fragment our freshwater ecosystems. These include low-head dams, road and railway crossings, and dykes and levees that block access to marshes, floodplains and other important off-channel habitats. Combined, these barriers have considerable effects on our freshwater ecosystems and the fish populations they support. They even affect other species, such as freshwater mussels that rely on fish to carry their larvae to new habitats.
The Canadian Wildlife Federation and our partners are working towards restoring the health of our freshwater ecosystems by removing barriers or modifying them so that fish and other aquatic organisms can pass. At the same time, we acknowledge that many barriers are vital parts of our society’s infrastructure and can play beneficial ecological roles, particularly in restricting the spread of aquatic invasive species. We work to identify the most important barriers to remediate and the right, cost-effective solutions for each barrier.