The alewife is a species of fish known as a river herring or shad, and is native to the East Coast of North America. Like American eels, alewife spend part of their lives in the ocean, but unlike the eels they are born in freshwater streams and rivers and spend their adult lives at sea (making them anadromous). When it’s time to spawn, the alewife return to inland freshwater systems, often to the very same rivers and streams where they were born. Historically their numbers were so vast that rivers like the Bronx River were said to “run silver” during their spring migration. However, due to the presence of dams and the general destruction of their habitat, as well as fishing and rebounding populations of predator fish like striped bass, alewife populations have declined significantly. In the Bronx River, the construction of a fish ladder, which resembles a small waterslide, at the historic dam at River Park, helps alewife climb over the dam and complete their migrations. Efforts by the Bronx River Alliance to restock the Bronx River with Alewife aim to restore their population.