When the dam’s away, the fish will play: Demolition on Brandywine Creek is restoring shad

For the first time in more than a century, American shad are spawning in the Brandywine Creek once again.

American shad — silvery, lightly spotted fish that spend most of their life cycle in the Atlantic and swim upriver to spawn — were once an abundant food source in the Delaware Valley. But in the 1970s, overfishing, pollution and dams impeding the migration process began to diminish their habitat and take a toll on the species. 

Governmental catch restrictions and waterway regulation have begun to restore the shad to their natural migration patterns. The only thing standing in their way now, both literally and figuratively, are a series of dams.

That, too, is changing. Recent dam demolition has led to the return of shad in New Jersey’s Paulins Kill and Musconetcong rivers, and a nonprofit called Brandywine Shad 2020 is campaigning actively to remove or modify all of the 10 remaining dams on the stretch of the Brandywine Creek in Delaware over the next three years.

It’s working so far. On July 28, Brandywine Shad 2020 co-founder Jim Shanahan said, researchers caught 159 juvenile and three adult shad just upstream of the place where the West Street Dam was removed by the City of Wilmington last year. If the rest of the dams are removed, it would be the first time fish were allowed to migrate freely since the first dams were built by European settlers to power mills as long ago as 1740.

“It’s really more than the shad,” Shanahan said Wednesday. “When you open up these rivers and return them to a free-flowing state, it changes the whole ecology of that quarter.”

Natural predators like ospreys and bass feed on the American shad, while pollution-reducing mussels attach their eggs to the shads’ gills and travel up the river. Shanahan lives on the Brandywine Creek — just the other day, he saw an osprey swoop down to feed on the young fish. 

“Wham! It banged down and pulled that sucker up,” he said. The removal of the Wilmington barrier “opened up a 0.8-mile stretch of habitat … it’s restoring the river in general to its natural state.”

Scientists from the University of Delaware, funded by the National Oceanic and Atmospheric Administration, are conducting bimonthly catches to monitor shad migration through mid-October. On Aug. 11, they caught only one shad, which they attributed to a storm-related increase in flow that made it hard for the fish to swim upstream. Their next catch is scheduled for August 25, when Shanahan is hoping to see larger numbers again.

In the past 20 years, 1,268 dams have been removed to restore natural river flow, ecological function, and fish passage, according to data from the nonprofit organization American Rivers. Of those dam removals, 290 were in Pennsylvania, 33 were in New Jersey, and two were in Delaware.

Dam removal isn’t always popular —  it can change the flow that locals are used to — but experts say it’s almost universally better to restore affected rivers and creeks. In addition to impeding the migration of fish like the American shad, human-made barriers can alter the water’s natural flow, force accumulation of sediment and disruption of natural habitat, and make the water warmer.