Tappen Zee Ecology


If you’re paddling south of the Tappan Zee Bridge on a warm summer day, you may be startled when what appears to be a large log suddenly breaches the surface and then vanishes to feed on the bottom of the Hudson River. That “log” is a sturgeon (either the smaller short nose Atlantic Acipenser brevirostrum or the Atlantic A. oxyrhinus). The Atlantic sturgeon are the largest fish in the Hudson and some can grow to be eight feet long and weigh 200 lbs. Both species have whisker-like barbels instead of teeth, armored plates instead of scales, and leathery skin. These primitive fish date back some 40 million years. 

Sturgeon were so abundant in the 17th century that they were considered food for the masses. By the 1880s, however, they were coveted for their roe (caviar) and appeared on menus in top restaurants as “Albany beef.” The overfished sturgeon dwindled but survived as the Hudson became a major industrial dumping ground, a commercial waterway servicing a city of more than eight million people, and a major world harbor. The fish even made a bit of a comeback during World War One when sailors and vessels were diverted from commercial fishing to warfare. Today, sturgeon are on the front lines of the battle for Hudson River environmental conservation, and the Atlantic Sturgeon is the official logo of the Hudson River Estuary. 

The size and longevity of these primordial fish should not be mistaken for resilience. Shortnose and Atlantic sturgeon are on the endangered species list 
and are threatened by construction of the new 
Tappan Zee Bridge. 

Sturgeon are anadramous, meaning they migrate from salt water to fresh water to spawn. They swim over 150 miles from New York Harbor, as far as the Federal Dam at Troy, to lay their eggs in April and May. Young sturgeon cross-commute in a reverse migration down the river to the Long Island Sound. 

Sturgeon are slow to reach sexual maturity (they spawn when they are 9–23 years old) and slow to recover from harm. 

Strict environmental conservation rules forbid dredging during spawning season (dredging is allowed only from August 1 to November 1). Pile driving, however, is not restricted, and the impact of the noise may kill these gentle giants and other fish that are crucial to the ecosystem of the Hudson River and environs. A thousand steel piles, each some 300 feet long and six feet in diameter, will be hydraulically pounded into bedrock or dense river muck. The impact of the pile driving sends out shock waves that can stun sturgeon or kill them outright by blowing up their air bladders. 

Kris McShane has trawled the Hudson tagging sturgeon for the Department of Environmental Conservation. He said these shock waves from pile driving may also be a barrier for adult sturgeon migrating to spawn sites, as well as a risk to young fish heading back downriver. The increased commercial boat and barge traffic associated with bridge construction means more sturgeon are likely to be hit and 
killed, as well. 

McShane has spent a lot of hours looking at fish. He observed, “Shad and herring are fragile. You’ve got to smile at them or they’ll die. The Hudson is also home to little glass eels that look like 3-inch strands of spaghetti. Think they’ll survive this? The fact is we just don’t know.” 

Steps are being taken to reduce the impact. The Department of Environmental Conservation and the National Marine Fisheries Services tag sturgeon and move them beyond the construction zone. Acoustic receivers installed along the bottom of the Hudson River from the George Washington Bridge to Stony Point track the movement of tagged fish. To muffle the blows of the pile driving, bridge workers wrap each pile in a “bubble curtain,” an enclosure containing a compressor that emits bubbles. This experiment with a “white noise” machine for fish will be evaluated by monitoring sturgeon migration and mortality. 

The Tappan Zee Bridge is long past its “sell-by date.” Bridge construction began in 1952, during the Korean War, when materials were scarce. The bridge was only designed to last 50 years. Deferred maintenance and replacement of neglected infrastructure have resulted in tragedies elsewhere in America where rotting bridges have come tumbling down. There’s a tension between protecting river life and human lives. Finding the right balance is essential to minimizing the environmental impact of construction. 

Riverkeeper and Scenic Hudson are two organizations that have lobbied for environmental safeguards on the project. These include a multi-million dollar fund to restore oyster reefs, tidal wetlands, fish spawning habitats, and natural shorelines. Inwood Canoe Club members can play a valuable role by observing life in, on, and along the river during bridge construction.