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From the December 2002 Conservationist

Hudson River Canoeing at Tivoli Bay

By John J. Rashak

The Hudson River National Estuarine Research Reserve (HRNERR) includes almost 5,000 acres of diverse wetland communities in four sites. HRNERR has set up unique three-hour canoeing programs that help people explore three of the four sites. The southern-most site, Piermont Marsh, is not included in the program.

I explored these sites by canoe with several interested citizens and Student Conservation Association (SCA) staff, who acted as able ecological interpreters on our trips.

SCA staff are assigned to various organizations, such as DEC's HRNERR and Five Rivers Environmental Education Center.

On three separate trips over the course of 10 days, I discovered the HRNERR canoe program to be a valuable and powerful way to appreciate the uniqueness, fragility, and beauty of the Hudson River ecosystem. Gliding along on the river helped make the group feel at home with the flora and fauna around us.

Trip One: The Bays of Tivoli

Tivoli Bays in Dutchess County, with more than 1,700 acres, is the largest site. Tivoli North Bay is a mature marsh with branching tidal creeks separated by vegetated banks. North Bay has hundreds of acres of cattails. In contrast, South Bay is shallow and open, with little evidence of tidal creeks and few cattails.

Our group of participants and volunteer guides set out from Stony Creek in four aluminum canoes. Canoes are ideal for exploring wetlands, since they need only six inches of water to float a quarter-ton load.

As we paddled toward a wide tidal channel, we saw three common marsh plants with arrow-shaped leaves: arrow arum (Peltandra virginica), arrowhead (Sagittaria latifolia), and pickerelweed (Pontederia cordata). We also saw spatterdock or yellow water-lily (Nuphar advena), which has large, shiny, heart-shaped, floating leaves. As we continued, we gazed at the Catskill Mountains, which rise dramatically 10 miles to the west.

The dominant plant in North Bay is the narrowleaf cattail (Typha angustifolia), which has several common names and many beneficial uses. Cattails provide wildlife with food and shelter. Geese, ducks and muskrats eat the starchy roots and birds eat the small seeds. Several common marsh birds nest in the cattails' stalks. Many insects use cattails for food and shelter. Cattails contribute to water quality by absorbing nitrogen and phosphorus and add to the food chain by releasing organic matter when they die.

Underwater plants along our route include water celery (Vallisneria americana), which was hard to see through the murky marsh water.

North Bay is a nursery. Nutrients and plant debris from the nearby uplands feed the marsh from the east, while other nutrients wash in from the tidal Hudson River to the west. These nutrients sink to the bottom, mix with decaying matter from dying marsh plants and create a rich food matrix. The matrix supports microscopic plankton such as algae, minute crustaceans, other invertebrates and aquatic plants. Tiny fish, such as killifish, feed at all water levels of the marsh. In turn, many predators eat the fish.

Snapping Turtle

One of the top predators in Tivoli North Bay is the common snapping turtle, or snapper, which lives in fresh or slightly brackish waters that support aquatic plants. The snapper (Chelydra serpentina; literally "snakelike swampbeast") prefers slow-moving water with a muddy bottom, but also inhabits rivers. A few smaller species, such as painted, wood, and map turtles also inhabit Tivoli Bays.

Although the snapper often flees if confronted in the water, it is can be aggressive on land. The fact that its upper and lower shells leave part of its body exposed may contribute to this behavior. Unlike most other turtles, the snapper cannot pull its fist-sized head fully into its shell. The snapper's jaws are covered with a sharp-edged horny sheath. Snappers are omnivorous and eat nearly anything organic. The record snapper taken from Tivoli North Bay weighted 44 pounds. Tivoli snappers, on average, live about 50 years.

Most turtles, whether aquatic or terrestrial, lay their eggs on land. Tivoli snappers prefer the open strip of cinders and soil along the railroad embankment between the marsh and the river. Here, their nests receive plenty of sunlight and the soil is soft enough for digging. Snappers hibernate each winter in bottom muck, muskrat riverbank dens, and under old hunting blinds.

New Islands and Water Chestnuts

Soon, we came to the railroad causeway between us and Magdalen Island to the west and Cruger Island to the south. My canoe-mates and I decided to briefly separate from the larger group to paddle under the causeway for a closer look at Magalen Island. We enjoyed the view south to the Kingston-Rhinecliff bridge without leaving our seats.

When we returned to the group, they were discussing water chestnuts (Trapa natans). In Eurasia, the water chestnut way prized for its high-protein edible nuts as well as its pleasing appearance. Introduced as an ornamental in an upstate New York pond in the late 1800s, the water chestnut was carried into the Mohawk River by a flood and spread to the Hudson River. Within 60 years, the species was found all over the Northeast. It is a notoriously invasive plant.

The dense mats of water chestnut shade other plants such as native water celery and Eurasian water milfoil, which wildlife use as food. Unfortunately, waterfowl cannot eat the water chestnut. Water chestnuts also reduce dissolved oxygen levels in the water column. Their tough underwater stems impede the passage of boats.

The Purple Peril

We observed another invasive plant-purple loosestrife (Lythrum salicaria). Like water chestnut, purple loosestrife came from Eurasia in the late 1800s and was deliberately introduced as an ornamental plant.

Loosestrife-sometimes called the Purple Peril-has beautiful purple flower spikes and propagates quite easily; so easily that it is crowding out native wetland plants, such as cattails, sedges and bulrushes. Muskrats and other marsh inhabitants eat cattails and bulrushes, but generally avoid loosestrife. Large cattail stands are essential or preferred nesting habitat for many marsh birds. On the other hand, red-winged blackbirds and American goldfinches nest in loosestrife, while deer and many insects eat it.

As I returned to the stony Creek launch site late that afternoon, I pondered the complex issues surrounding invasive plants and the ecosystems on which they encroach.

Trip Two: Iona Island and Doodletown Brook

Nine days later, the group convened at HRNERR's Iona Island marsh in Rockland County. This site is now part of Bear Mountain State Park.

Wheras Tivoli Bays are dominated by two large river coves partially surrounded by wooded clay bluffs on the east side of the river, the Iona Island Marsh site features a bedrock island on the west side of the river in the midst of the Hudson Highlands. A known bald eagle roosting site, the island is closed in the winter.

We set off with seven canoes and about 18 people, including a few children. We began by visiting Doodletown Brook, the principal tributary to the site. Soon, we had an excellent view of the Bear Mountain Bridge to the north. We saw Bear Mountain to the west of the bridge, and another mountain, Anthony's Nose, to the east.

We passed under the railroad tracks which run up the west side of the river and paddled the main stem of the Hudson for a long mile. Despite the fatigue brought on by an hours of heavy paddling, we were invigorated by sunshine that broke through some early could. We circled the southeast corner of Iona Island and found another pass beneath the railroad tracks.

We gunneled up for some words from our SCA interpreters about the Salisbury and Ring Meadows; two large tidal marshes to which we had returned. Wee again saw narrow-leaved cattail and the common reed (Phragmites australis). Tall, dense stands of Phragmites seem to decrease the number of plant and animal species in the brackish and freshwater tidal portions of the Hudson estuary.

Trip Three: Stockport Flats and the No-Name Islands

With six canoes and 18 people, we put out again the next morning from Stockport Flats, about three miles north of the city of Hudson. Stockport Flats is a five-mile shoreline mosaic of marshes, shallows, sandy islands and tidal swamps. The islands were built from piles of sediment, dredged from the river bottom of barges specially built to keep navigation lanes open.

Our paddling was thwarted by the marshes and swamps east of our launch site, so we reversed our course and went west. After passing beneath a large railroad bridge near where we began an hour earlier, we headed for a dredge-derived island. We didn't know the name of the island, but there were some trees and, on the east and west sides, campsites.

We stopped at a west-side campsite to wade in the river. Then, I followed a rough trail inland for a short distance. The fertility of river-bottom sediment was evidenced by the immense size of the trees along this path.

We left the island before noon, just as the sun was breaking through the clouds. We paddled carefully to avoid the lines of fishermen on the north bridge pier. Our canoe put-in on stockport Creek was just around the far corner of this pier.

We loaded the canoes on the trailer and said our goodbyes. As I walked back to my car, I looked west at the Stockport Flats section of the river, and I could see that water chestnuts covered much of the water's surface.

I wondered then about the future of the estuary, and the interplay between native and non-native plants. Certainly, the HRNERR canoe exploration program has made clear the importance of the estuary to other local ecosystems. However, it also became clear to me that preserving the biodiversity of the estuary itself might be HRNERR's most important mission.

A Place For Research and Exploration

As part of a nationwide system of over 20 estuarine research reserves in 17 coastal states and Puerto Rico, areas of New York's tidal wetlands have been set aside as field laboratories for estuarine research and education. A network of four distinct sites (known collectively as the Hudson River National Estuarine Research Reserve, or HRNERR) were set aside in 1982.

On-site public education and interpretation programs include year-round field programs for adult audiences, field classes for students, workshops for teachers and youth leaders, traveling exhibits, and presentations to community groups and service organizations.

Interpretive exhibits are located at the Trailside Museum and Zoo near Iona Island in Bear Mountain State Park and at the Coxsackie boat launch near Stockport Flats.

The New York State Department of Environmental conservation has lead responsibility for managing the HRNERR. For more information, please contact the NRNERR at (845) 758-7010.

John J. Rashak is a DEC environmental engineer. He has a great interest in ecosystem research, which has led him to explore all seven continents.

Photo: John J. Rashak