Rahway River migrations. Fish ladders are inundated structures with small underwater steps that allow fish to navigate around a dam and continue their migration. Other approaches include removing obstructions that are inoperative or no longer serve their purpose, or improving water quality and reducing debris that obstructs passage. The fish targeted for upstream passage at the Rahway River Water Supply Dam are alewife (Alosa pseudoharengus), blueback herring (Alosa aestivalis), gizzard shad (Dorosoma cepedianum), white perch (Morone Americana) and the endangered American eel (Anguilla rostrate). Alewife and blueback herring are collectively referred to as river herring due to their similarity in appearance, range,
Herring also found in the Arabian Sea, Indian Ocean, and Bay of Bengal. Herring played a pivotal role in the history of marine fisheries in Europe, and early in the 20th century, their study was fundamental to the evolution of fisheries science. These oily fish also have a long history as an important food fish, and are often salted, smoked, or pickled. A number of different species, most belonging to the family Clupeidae, are commonly referred to as herrings. The origins of the term "herring" is somewhat unclear, though it may derive from the Old High German "heri" meaning a "host,