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,
West African pygmy herring West African pygmy herring The West African pygmy herring ("Sierrathrissa leonensis") is a very small fish, reaching a maximum length of SL, is a member of the herring family Clupeidae, and belongs to a radiation of the subfamily Pellonulinae in the freshwater systems of western and central Africa that includes such species as the "Microthrissa royauxi" of the Congo River basin and "Limnothrissa miodon" of Lake Tanganyika. It is the only species of its genus. A very small fish which shows a reduction in size and some neoteny when compared to its larger relatives. The West African pygmy herring is