Saturday, July 2, 2011

Fish of the Week: Alewife Herring

Alewife (Alosa pseudoharengus)

Quoting from information from the Bronx River Alliance:

Here in the Bronx River the silvery alewife is an important part of the river’s ecosystem. It is a major food source for bluefish and striped bass, schools of which will often follow the returning alewives for many miles up estuaries and rivers. The alewife is also eaten by such spectacular birds as herons, ospreys, cormorants, and even bald eagles – and they’re healthier for them, too, since they return from the ocean with fewer toxins in their bodies than most freshwater fishes. They also feed eels, gulls, raccoons, crayfish, and turtles, and as the only known host for the freshwater mussel known as the “alewife floater,” the alewife may help reestablish this native population of filter feeders that will help clean the water.

Ranging from Newfoundland to South Carolina, the alewife is spawned in fresh or brackish water, after which both juveniles and adults return to the ocean until the next spring, when they return to the very waters in which they themselves were spawned in to begin a new round of their life cycle. A single alewife may do this for as many as seven or eight years in succession.

The alewife herring is not just a native to the Bronx River, but also the Hudson, Sound, Chesapeake Bay, and other marine estuaries from the Mid-Atlantic up to Nova Scotia. Some populations are landlocked and they are even considered an invasive pest in the Great Lakes. However the herring were once a welcome annual food source to the Native Americans and Pilgrims, until the rivers, both Hudson and Bronx, became polluted. The Bronx River has been dammed up in several places making the upstream migration for spawning impossible, and until recent environmental efforts to clean up the river, the Bronx River was practically an open sewer for waste and garbage.

However the Wildlife Conservation Society and New York City Department of Parks have been working together since 2006 to reintroduce the herring as a sort of experiment to see if a population could be sustained in the newly cleaned waters. (Previously the herring had not been seen in the Bronx River for nearly 350 years!!)

In 2009 seven herring were found to have returned to the Bronx River after a few years in marine waters. Scientists think that these fish return to their juvenile waters by following chemical markers in the water (they smell their way home!). The journey is remarkable and baffling to those of us who lose our way even with maps, street signs, and directions to our destination. The experiment proves that the fish CAN survive in the Bronx River, and not only that, they can make it to sea to mature and make it back to spawn. The problem is those pesky dams, some of which date back to colonial days when the river was used to power flour mills. Constructing "ladders" (they are more like water slides) for the fish to make it over the dams is expensive. For historic preservation reasons, I am guessing the city is reluctant to dismantle those stone dams which go back centuries.

This tiny article in the New York Daily News documents that ecologists working for the Bronx River Alliance was able to find alewife herring in the River for a second year in a row in April 2010. My question is, how has 2011 fared? Are the herring still returning? Are they able to spawn successfully in spite of the dams? How many have returned? I have just emailed a New York City Parks project manager to try to obtain more information on this. Before we celebrate the return of herring to the Bronx River, I need to ascertain that they are in fact still there. Then we need to think about how we can keep the population going and healthy.

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