Fish and Aquatic Conservation
Citico Dam Removal Before and After. Photo Credit: USFWS


What is Fish Passage?

photo of a fish swimming in a shaded channel
This small shaded side channel was restored to provide appropriate water levels and flows for rearing juvenile salmonids.. Photo Credit: Beth Campbell/USFWS


Fish need to move. They need connections between and within waterways during various life stages to reproduce, feed, and contribute to their ecosystems by recycling the nutrients they take in. Each year millions of fish migrate between the ocean and their native habitats to spawn. Some fish move within a river system to find food or refuge from warmer water. Other aquatic wildlife, like mussels, also depend on the ability to move from place to place in order to survive.

Fish passage is the ability of fish or other aquatic species to move throughout an aquatic system among all habitats necessary to complete their life cycle. We can restore fish passage by removing in-stream barriers or replacing them with structures that allow fish to pass. When fish and other aquatic species can’t migrate or have access to important habitat, they can’t reproduce and build sustainable populations. Some populations are so affected by barriers that they are listed as a threatened or endangered species, or may even become extinct. An example is the Atlantic salmon. Once plentiful and found in almost every river north of the Hudson River, today only a small percentage of their historic population remains. One major cause of their decline was the barriers that prevented these fish from reaching important spawning habitat.

Improving fish passage is good for fish, and for people too. By allowing rivers to flow naturally, barrier removal can help manage and reduce flooding. Removing barriers like dams that are potential hazards make the waterways safer and can increase boating opportunities. Replacing road stream crossings with structures that can better withstand storms brings economic benefits to local communities, as these structures are less likely to blow out in floods and need less maintenance.

Other barrier removal benefits include building sustainable fish populations that improve recreational and commercial fishing. Some fish that benefit from barrier removals, such as the Eastern brook trout, are key to the recreational fishing industry and associated tourism. Other fish, like the migratory shad and river herring, are prey for larger commercial and recreational species. The commercial and recreational fishing industries support more than 2 million jobs and generate billions in sales each year in the U.S. 

Removal also improves lives of tribal cultures like those along the Klamath River Basin in California and Oregon. The salmon that migrate in the Klamath are the source of the tribe’s food, income, and are at the heart of their ceremonies. There have been recent cases where tribes have not been allowed to fish their ancestral waters because of decreases in fish populations, which are due in part to the presence of dams.

What is a barrier?

A barrier is anything prevents or reduces the ability of aquatic species to move where needed to survive and complete their life cycle. This includes physical barriers, such as dams, culverts, and levees, and environmental barriers such as excess sediment, poor water quality, and temperature or flow variations.

Types of barriers:

Photo of a Culvert
Photo of a Culvert
Photo of a Culvert
Photo of a Culvert

Photo of a  Dam
Photo of a  Dam
Photo of Water Diversion
Photo of Water Diversion

Photo of a Levee
Photo of a Fish Screen
Photo of a Fish Screen
Photo of a Velocity Barrier