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.