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American shad were a major food source for early European settlers and Native Americans who lived along the Delaware River.
Known as “America’s founding fish,” the species were so abundant that it was said people could “walk across their backs.” In 1896, more than 4 million shad were caught in a single year. But by the 1900s, overfishing caused a steep decline.
A new study published this month indicates that American shad, as well as river herring, have failed to recover in the Delaware River, which could threaten the aquatic ecosystem.
Today, the migratory fish face threats such as dams that impact their ability to travel and reproduce, as well as low oxygen levels caused by ammonia discharges from wastewater facilities into the river. As a result, populations of the fish are close to record lows in eastern North America.
“Shad and river herring are iconic species in the Delaware estuary, and seeing them in such low numbers, as an ecologist, is concerning,” said LeeAnn Haaf, estuary science director at the Partnership for the Delaware Estuary.
The study was a collaboration between the Partnership for the Delaware Estuary, the U.S. Fish and Wildlife Service, the Philadelphia Water Department, the Pennsylvania Fish and Boat Commission and PSEG Nuclear, which operates the Salem and Hope Creek nuclear power plants along the river in Alloway Township, New Jersey.
“These populations will still exist in some capacity, but in terms of people being able to recreate or enjoy these species, there’s going to be so many regulations on their populations to keep them functional that people aren’t going to be able to be allowed to fish for them,” said co-author Ella Rothermel, urban resilience assistant manager at the Partnership for the Delaware Estuary.
“People used to be able to witness these migrations, but that’s not really feasible to do at this point, either because of dams or low population numbers,” she added.
American shad, along with alewife and blueback herring, collectively termed “river herring”, migrate to the Delaware River’s tributaries to spawn. They are a critical food source for larger fish like striped bass, as well as bears, raptors, cormorants and gulls. They help with nutrient cycling and act as a host fish for freshwater mussels.
