Saw Mill River Daylighting - Fish Passage

Saw Mill River Daylighting

A Fish Passage

 

What looks like a ladder to the right of where you are standing really IS a ladder-an Alaskan Steep Pass fish ladder. It was placed here to allow the American eel, Anguilla rostrata, and the alewife (river herring). Alosa pseudoharengus, to swim upstream. The concrete "stairway" just next to the fish ladder is unsuitable for upstream fish migration because there are no resting pools between steps to allow fish to gather strength between leaps.

Both the American eel and the alewife are Hudson River "signature species"-without their existence, the Hudson wouldn't BE the Hudson! The daylighting project was carefully planned so that both eels and alewives can migrate upstream and return safely downstream.

 

 

Each spring, the Saw Mill River is home to millions of tiny glass eels. Born 600 miles away in an area of the Atlantic Ocean called the Sargasso Sea, 2- to 3-inch transparent baby eels come to the Eastern Seaboard seeking freshwater rivers. They make their way up the Hudson to Yonkers, where they enter the Saw Mill River.

Some 5 to 20 years later, the mature adult eel swims back down the river and returns to the Sargasso Sea to spawn. It is the ONLY North American fish to do this-growing up in fresh water and spawning in salt water-and thus is called a "catadromous" fish.

 

Eels help the ecosystem by eating dead fish, invertebrates, carrion and insects. Adult female eels typically grow to 5 feet in length and produce 20 million eggs. The male eel usually reaches about 3 feet. The world record weight for an American eel is 9.25 pounds. Amazingly, they are able to breathe on land and climb up vertical walls. Eels have been found at Woodlands Lake, above a 20-foot-high dam, 7½ miles upriver from where you are standing.

 

 

Alewives and eels migrate in opposite directions. Alewives spawn in freshwater rivers and swim out to sea to mature, a much more common life cycle for fish called "anadromous." They congregate each year at the mouth of the Saw Mill River, but in the past had no chance of getting upstream because originally there was a steep waterfall. The fish ladder and the gradual slope of the new stream bed design should aid them in their attempt to swim upriver to find suitable spawning habitat.

 

Interpretive signs developed for the City of Yonkers by Groundwork Hudson Valley, Friends of Philipse Manor Hall, Yonkers Historical Society and Yonkers Public Library.

 

Submitted by @lampbane