Bronx River - Ecology

Ecology

Local alewife, taken from a coastal tributary in nearby Connecticut, were released in the river in March 2006. The alewife were expected to spawn in the river's headwaters. Their offspring would spend the summer in the river, migrate out to sea in the fall, and in three to five years return, like all anadromous fishes, to their spawning grounds. Stocking was intended to be repeated annually for the following five years, to build up the new resident population. The fishes, among a group called "river herring," feed low on the food-chain and help reduce eutrophication. And in fact, several adult alewife were found below the first dam on the river on April 7, 2009. As an analysis revealed they were 3 years old, the assumption of scientists is that these were in fact descendants of the alewife released 3 years before in March 2006. The next step will be to erect fish ladders over the 3 dams lowest on the river, allowing the alewife access to a portion of the river with more suitable spawning habitat.

In February 2007 biologists with the Wildlife Conservation Society, which operates the Zoo, spotted a beaver (Castor canadensis) in the river. "There has not been a sighting of a beaver lodge or a beaver in New York City for over 200 years. It sounds fantastic, but one of the messages that comes out of this is if you give wildlife a chance it will come back," said John Calvelli, a spokesman for the Society. The beaver is named Jose Serrano, after the Congressman, and has been sighted below the East Tremont bridge at Drew Gardens as recently as June, 2009. Beaver have not lived in New York City since the early 19th century when trappers extirpated them completely from the state. In the summer of 2010 a second beaver joined Jose, doubling the beaver population in New York City. Beaver were once important to the city's economy and pair of beaver appear on the city's official seal and flag.