Migratory Fish Species

American Eel (Anguilla rostrata) – Native
Family Anguillidae

The American Eel is an important keystone species in the Upper Delaware River. American Eels are catadromous, meaning they migrate down river to spawn in the ocean. They hatch in the Sargasso Sea within the Northern Atlantic Ocean but then travel to freshwater streams where they mature and spend most of their lives. After years or even decades, they eventually return to the Sargasso Sea to spawn. American Eels are generally carnivorous and feed on insects, fish, fish eggs, crabs, worms, clams, and frogs.The Eastern Elliptio mussel (Elliptio complanata), which is important for keeping the waters of the Upper Delaware clean through its water filtering capacity, uses the American Eel as its main host for reproduction. Eastern Elliptio larvae, known as glochidia, attach to the gills of the American Eel and remain there until they metamorphose into juvenile mussels.

 

American Eel

National Park Service

 

American Shad

Joe Demalderis

American Shad (Alosa sapidissima) – Native
Family Clupeidae

The American Shad is a silver fish with a greenish-blue metallic sheen on its back. The scales easily detach, and its thin mouth tissue is easily torn. American Shad are anadromous, meaning they live in the ocean and swim upstream to spawn in freshwater rivers. Each spring, adult shad “run” up the Delaware River to spawn. American Shad spawn at night over sandbars or riffles. Females lay an average of 100,000 eggs and the eggs drift along with the current before hatching. Juveniles spend months in freshwater rivers and then return to the ocean in late summer and fall. Their diet consists of microcrustaceans, worms, insect larvae, and small fish.

 

Sea Lamprey

National Park Service

Sea Lamprey (Petromyzon marinus) - Native
Family Petromyzontidae

The Sea Lamprey is a jawless fish with a thin cylindrical body that superficially resembles an eel or snake. They may grow to three feet in length. Lampreys are considered the most primitive of all vertebrates. Sea Lampreys are anadromous and move up the Delaware River from the Atlantic Ocean to spawn. Like freshwater mussels, larvae filter-feed on plankton and other small particles. Adults are parasitic and feed by attaching their suction-cup mouth to the exterior of a host fish and then rasping away the fish’s skin with their tongue and consuming its blood and body fluids.

 

Striped Bass

Evan Padua

Striped Bass (Morone saxatilis) – Native
Family Moronidae

The Striped Bass is a silver fish with olive green to blue gray back and white to silver underside. Striped Bass have six to seven dark stripes running horizontally along their body. They are anadromous and migrate upstream through freshwater rivers from the ocean or saltwater bays to spawn. Spawning and courtship rituals of the Striped Bass appear to be slightly chaotic with frantic spawning and swimming. It is essential that Striped Bass eggs stay in motion and move along with the river current. If the eggs sink to the bottom of the river, they often become covered in debris and die. Striped Bass are opportunistic predators with a diverse diet consisting of microcrustaceans, midge larvae, large crustaceans, mollusks, and other fish species.