Fish Passage
A Denil fishway, one type of fish passageway, is a series of sloped channels which allow the fish to swim over the dam or obstruction.
Physical structures that block or impede fish migrations to historic upstream spawning habitats are potentially the most important factor in the decline of migratory fish populations in the Bay. Over 5,000 miles of fish spawning habitat on Bay tributaries are currently blocked by dams, culverts and other man-made obstructions.
By removing dams or installing fish lifts, ladders and other passageways, migratory fish like American shad, river herring, American eels and white and yellow perch are able to return to upstream spawning and nursery grounds. Resident fish like bass, walleye and catfish also benefit from the removal of fish passage blockages in rivers.
Current Restoration Goal
From 1988 through 2005, Bay Program partners restored 1,838 miles of fish passage, surpassing their original 1,357-mile restoration goal. The fish passage restoration goal has since been increased to 2,807 miles by 2014.
During the first three years of the new fish passage goal (2005 to 2007), partners completed 40 projects that opened 460 miles of historic spawning habitat, bringing the total to 2,266 miles opened, or 81 percent of the restoration goal.
Priority is given to fish passage restoration projects that:
- Open larger stretches of highest quality habitat.
- Favor dam removals as opposed to building artificial fish passages, where practical.
- Enhance passage of migratory fish over resident fish; and/or have shad and herring stocking programs taking place.
- Favor removal of impediments in streams that have been impaired by acid mine drainage. In these locations, water quality improvements will support a diverse array of fish and other aquatic species.
Whenever possible, fish passage projects are integrated with locally supported watershed management plans.