From the mighty striped bass (Morone saxatilis) to the humble Eastern mudminnow (Umbra pygmaea), a wide variety of fish inhabit the clean waters of the Delaware River, tributary streams, lakes, ponds, and wetlands within this park.
A total of 61 species are known within the park. Ten of these species have been listed as rare, threatened, or endangered by the states of New Jersey and/or Pennsylvania. One additional species, the ironcolor shiner (Notropis chalybaeus), may also inhabit park waters. However, the last report of the ironcolor shiner in park waters was in 1978, and only one known population remains in Pennsylvania. Of the 61 total fish species, 44 are native to the region, 14 are native to North America but probably did not naturally occur in this region, and three are introduced alien species that are not native to North America.
The alien species are common carp (Cyprinus carpio), native to Asia and Europe, goldfish (Carassisauratus), native to Asia, and brown trout (Salmo trutta), native to Europe.
The native species most important for recreational fishing today include American shad (Alosa sapidissima) (above), brook trout (Salvelinus fontinalis), yellow perch (Perca flavescens), and pumpkinseed (Lepomis gibbosus).
Before the park was created, the following species were introduced to the region, and now inhabit park waters: brown trout, rainbow trout (Onchorhynchus mykiss) smallmouth bass (Micropterus dolomieu), largemouth bass (Micropterus salmoides), bluegill (Lepomis gibbosus), green sunfish (Lepomis cyanellus), black crappie (Pomoxis nigromaculatus), channel catfish (Ictalusrus punctatus), walleye (Stizostedion vitreum vitreum), muskellunge (Esox masquinongy), gizzard shad (Dorosoma cepeduanum), alewife (Alosa pseudoharengus), and fathead minnow (Pimephales promelas).
Fishing for many of these species is now a very popular recreational activity in the park. Four native "anadromous" species occur in the Delaware River within the park. Anadromous species begin their lives in freshwater, but later migrate to the ocean, where they spend the middle part of their lives; then migrate back to freshwater to spawn. The four anadromous species in the park are striped bass, American shad, blueback herring (Alosa aestivalis), and sea lamprey (Petromyzon marinus). Juvenile sea lamprey may remain in fresh water streams for 14 years before migrating to the ocean, whereas juveniles of our other anadromous species migrate to the ocean within the first year of life.
One "catadromous" species, American eel (Anguilla rostrata), occurs in the Delaware River within the park. Catadromous species begin their lives in the ocean, but migrate to freshwater, where they spend the middle part of their lives; then they migrate back to the ocean to spawn. Female American eels migrate from the Atlantic ocean into the Delaware River when they are about one year old, and typically remain for about 10 years. Unlike the females, it seems that male eels typically do not migrate into fresh water, but remain in the brackish waters of estuaries. Thus, it is likely that all -- or almost all -- American eels within park waters are females.