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Chesapeake Bay News

Apr
15
2014

Potomac River sees rise in returning shad, driving up Bay-wide abundance trend

Over the last decade, American shad abundance in the Potomac River has continued its consistent rise, driving the overall upward trend of shad abundance in the Chesapeake Bay. 

Image courtesy MTSOfan/Flickr

While shad spend most of their adult lives in the ocean, the anadromous fish migrate into freshwater rivers and streams to spawn. Since 2000, shad abundance in the Bay has increased from 9 percent of the goal to 41 percent of the goal, with the Potomac seeing the most consistent rise in returning shad. Between 2000 and 2013, shad abundance in the Potomac rose from 12.4 percent to 129.4 percent of the target. Scientists attribute this increase to a series of factors, including improvements in water quality; a resurgence in underwater grass beds; the installation of a fish passageway at Little Falls Dam; a moratorium on recreational shad harvest; stocking efforts that reprinted fish to the river and kick-started the population; and the overall suitability of the Potomac as shad habitat. 

“While there are several factors behind the shad recovery in the Potomac River, improved water quality is the cornerstone,” said Jim Cummins, director for living resources at the Interstate Commission on the Potomac River Basin (ICPRB) and co-chair of the Chesapeake Bay Program’s American Shad Indicator Action Team. “Without cleaner waters in the Potomac River, we would never have seen such a boost in returning shad. We’ve reached the sustainable fishery target for the river, but we are still working to achieve a more robust goal: to see the shad population healthy and fit, and to see the river run silver again. That’s not a ‘pristine river’ goal—that’s a goal we can achieve.”

The Bay Program tracks the abundance of shad in the James, Potomac, Rappahannock, Susquehanna and York rivers as an indicator of watershed health. Collectively, these five waterways account for about 90 percent of the Bay’s shad population, and each has its own population target.

While shad abundance is relatively high in the Rappahannock River—reaching 92.7 percent of the target in 2012 but falling to 88.9 percent of the target in 2013—abundance remains negligible in the upper James and Susquehanna and variable in the lower James and York. Some variability is natural, but the continued scarcity of shad in the upper James and Susquehanna can be attributed to large dams that block fish passage and mute some of the natural cues that send migratory fish upstream.

Once one of the most valuable fisheries in the Bay, shad populations have declined in recent decades due to pollution, historic overfishing and the construction of dams that block the fish from reaching their spawning grounds. Commercial shad harvest is now closed across most of the region, and Bay Program partners are working to remove dams, install passageways that allow shad to reach upstream habitats and restock waterways with hatchery-raised fish. In addition, students in Maryland, Virginia and the District of Columbia are raising shad and releasing them into the Potomac River, bringing public attention to the importance of the once-forgotten fish.

Overall, shad abundance in the Bay has increased from 8 percent of the goal in 2000 to 41 percent of the goal in 2013.

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