SIGNIFICANT HABITATS AND HABITAT
COMPLEXES
OF THE NEW YORK BIGHT WATERSHED
Mid-Hudson
River Estuary
COMPLEX #32
List of Species of Special Emphasis
I. SITE NAME: Mid-Hudson River Estuary
II. SITE LOCATION: The mid-Hudson River estuary is the portion of the Hudson River in southeastern New York extending from Stony Point north to Poughkeepsie.
TOWNS: Cornwall, Cortlandt, Fishkill, Highland, Lloyd, Marlborough, New Windsor, Newburgh, Phillipstown, Poughkeepsie, Stony Point, Wappinger
COUNTIES: Rockland, Westchester, Orange, Putnam, Dutchess, Ulster
STATE: New York
USGS 7.5 MIN QUADS: Peekskill, NY (41073-38), West Point (41073-48), Wappinger Falls (41073-58), Poughkeepsie (41073-68), Cornwall (41074-41), Newburgh (41074-51)
USGS 30 x 60 MIN QUADS: Bridgeport, CT-NY-NJ (41073-A1), Waterbury, CT-NY (41073-E1), Middletown, NY-NJ (41074-A1), Monticello, NY-PA (41074-E1)
III. BOUNDARY DESCRIPTION AND JUSTIFICATION: The significant habitat complex boundary for the mid-Hudson River estuary follows the shores of the Hudson River from Stony Point, river kilometer 66 (mile 41), to Poughkeepsie, river kilometer 120 (mile 75). The boundary of the complex includes all riverine and estuarine open water and tidal wetland habitat in this stretch of the Hudson which encompasses regionally significant spawning migratory and nursery habitat for anadromous, estuarine, and freshwater fish, important winter feeding and roosting areas for the federally listed endangered bald eagle, and globally and regionally rare brackish and freshwater tidal communities and plants.
IV. OWNERSHIP/PROTECTION/RECOGNITION: The uplands and shoreline of the mid-Hudson River estuary are in a mix of public and private ownership. Much of the shoreline where the Hudson passes through the New York - New Jersey Highlands (Highlands) is in public ownership (Harriman State Park, Bear Mountain State Park, Hudson Highlands State Park, Storm King State Park, West Point Military Academy, and Camp Smith Military Reservation), but the rest of the shoreline is substantially in private ownership. Underwater lands are owned by New York State through the Office of General Services. Wetlands are regulated in New York under the state's Freshwater Wetlands Act of 1975 and Tidal Wetlands Act of 1977; these statutes are in addition to federal regulation under Section 10 of the Rivers and Harbors Act of 1899, Section 404 of the Clean Water Act of 1977, and various Executive Orders. New York State has designated several Significant Coastal Fish and Wildlife Habitats in this stretch of the Hudson, including Iona Marsh, Hudson River Mile 44-56, Constitution Marsh, Moodna Creek, Fishkill Creek, Wappinger Creek, and Poughkeepsie Deepwater. The New York State Natural Heritage Program, in conjunction The Nature Conservancy, recognizes several Priority Sites for Biodiversity with the mid-Hudson River estuary habitat complex. These sites are listed here along with their biodiversity ranks: Poughkeepsie Deepwater Habitat (B2 - very high biodiversity significance), Con Hook (B3 - high biodiversity significance), Constitution Marsh (B3), Iona Island (B3), Mine Point (B3), and Moodna Creek Mouth (B3). Iona Island and Marsh complex has been designated by the National Oceanic and Atmospheric Administration and the New York State Department of Environmental Conservation as part of the Hudson River National Estuarine Research Reserve. Iona Island Marsh has also been recognized as a National Natural Landmark by the U.S. Department of Interior.
V. GENERAL AREA DESCRIPTION: The Hudson River can be divided into salinity habitat zones based on average annual salinities: the polyhaline (high salinity) zone from Manhattan north to Yonkers, the mesohaline (moderate salinity) zone from Yonkers north to Stony Point, the oligohaline (low salinity) zone from Stony Point north to about Wappinger Falls, and the tidal freshwater zone from Wappinger Falls north to the Troy Dam. These salinity zones vary greatly with the season; the salt front pushes as far south as the George Washington Bridge some years during high spring flows, and brackish water extends as far north as Poughkeepsie during summer low water flows. The Hudson River estuary is a tidally dominated system, with tidal flows from 10 to 100 times the total freshwater inflows. Salinity influences the distribution and function of both plants and animals within the Hudson Estuary. The distribution of tidal marsh communities and plants in the Hudson is influenced by surface water salinity during the growing season. Freshwater tidal marsh communities generally occur north of Newburgh-Beacon, brackish tidal marsh communities generally occur south of Newburgh-Beacon, and small remnant salt marshes occur south of Yonkers. The Hudson River is partially regulated by the Hudson River-Black River Regulating District, one goal of which is to minimize spring flooding in the upper Hudson (above the Troy dam) and to provide some augmentation flows during the low flow periods. A secondary goal is providing freshwater flows during drought conditions to assist in keeping the salt front below the freshwater intakes at Poughkeepsie. Benthic communities vary in distribution depending on bottom water salinity, with a typically marine benthos from Stony Point south dominated by marine worms and crustacea, a mixture of freshwater and marine organisms between Stony Point and Poughkeepsie, and freshwater snails, clams, chironomids, and insects north of Poughkeepsie. Coastal and estuarine fish species tolerate a wide range of salinities, while freshwater species can tolerate only a narrow range to live and reproduce successfully. Anadromous fish species require different salinities at the different phases of their life cycles.
The mid-estuary from Stony Point to Poughkeepsie is generally the oligohaline (0.5 to 5 parts per thousand salinity) zone in the Hudson, including the seasonal inland extent of brackish water in the Hudson, although the limits of this zone change with the amount of freshwater flow. The mid-estuary begins north of the wide bays region (Haverstraw Bay/Tappan Zee) at Stony Point at river kilometer 66 (mile 41). North of Peekskill at river kilometer 71 (river mile 44), the river passes into the Highlands where it narrows to an average width of about 550 meters (1,800 feet). This is a deep (15 to 60 meters [49 to 197 feet]) and turbulent mixing zone with little shoal area and steep shorelines. The adjacent uplands are steep, forested areas with limited development. At Cornwall, river kilometer 90 (river mile 56), the river passes out of the Highlands and widens to an average of 1.8 kilometers (1.1 miles). The average mid-channel depth is about 12 meters (40 feet). There are wider shoal areas along the shoreline, especially on the eastern shore, supporting growth of submerged aquatic vegetation (SAV). The adjacent uplands are more gently sloping, with a mix of forested, agricultural, and developed (residential, commercial, and industrial) land use. North of Wappinger Creek at river kilometer 108 (river mile 67), the river narrows again and increases in depth to as much as 38 meters (125 feet). Throughout the entire mid-estuary, there are railroads on either shoreline, cutting off embayments from the river and limiting access. Several cities occur on this portion of the river, including Peekskill, Newburgh, and Poughkeepsie.
The vegetational and faunal communities found in and along the Hudson depend on the river's depth and salinity. The deepwater tidal river zone occurs below the depths that support plant growth, about 2 meters (6 feet) in the turbid Hudson. Primary production in this zone comes only from phytoplankton. These deepwater zones generally have swift currents and rocky bottoms. The two sections of deepwater within the mid-estuary are Hudson River 44-56 and the Poughkeepsie Deepwater. The shallow subtidal zone occurs below mean low tide but above the deepwater zone. Submerged aquatic vegetation may occur in narrow, shallow, subtidal bands along the shoreline and in a few wider shoals areas such the shoals along the Fishkill-Beacon shoreline. Characteristic plants include waterweed (Elodea nuttallii), coontail (Ceratophyllum demersum), naiad (Najas guadalupensis), sago pondweed (Potamogeton pectinatus), horned pondweed (Zannichellia palustris), and widgeon grass (Ruppia maritima). Water chestnut occupies substantial portions of this part of the river from river kilometer 93 (river mile 58) (Pollapel Island) north to about river kilometer 105 (river mile 65) (Chelsea). The tidal zone in the Hudson consists of sparsely vegetated intertidal shore and flats and tidal marsh communities. Because of the generally steep shoreline, deep water, and strong currents in this stretch of the river, marshes and flats occur only at the mouths of tributaries or in the shelter of islands where sediment can accumulate. The four major tributaries in this part of the Hudson are from south to north: Annsville Creek, Moodna Creek, Fishkill Creek, and Wappinger Creek. Marshes and tidal flats occur at these tributary mouths and behind Iona Island, Constitution Island, and Con Hook. Mudflats contain arrowheads (Sagittaria spp.), wild celery (Vallisneria americana), and mud-plantain (Heteranthera reniformis), as well as diverse assemblages of periphyton (attached algae) and bacteria. Freshwater mudflats found from Wappinger Creek north contain several of these species as well as mudwort (Limosella australis). Brackish and freshwater marshes in the Hudson can generally be divided into lower and upper marsh zones. The lower marsh generally experiences large daily fluctuations in water levels and is characterized by peltate-leaved plants (broad leaves on long stalks arising from the plant's base). Characteristic plants include spatterdock (Nuphar advena) in deeper water interspersed with pickerelweed (Pontedaria cordata), big-leaved arrowhead (Sagittaria latifolia), and arrow arum (Peltandra virginica) in shallower water. In areas with sandy substrate, common three-square bulrush (Scirpus pungens), water smartweeds (Polygonum amphibium), and bur-marigolds (Bidens spp.) are characteristic. The upper marsh is only partially flooded during the daily tidal cycle and is characterized by an emergent marsh community. Dominant plants are narrow-leaved cattail (Typha angustifolia) and the invasive common reed (Phragmites australis). In the wetter areas of the upper marsh, the cattail and reed are mixed with wild rice (Zizania aquatica), rice cut grass (Leersia oryzoides), river bulrush (Scirpus fluviatilis), and sweet flag (Acorus americanus).
In addition to the important marsh communities occurring at the mouths, tributaries provide freshwater inflow into the Hudson system, spawning habitat for herrings, and overwintering areas for black bass (Microterus spp.). The adjacent uplands along the mid-estuary shoreline, especially in the Highlands, support a variety of rare plant and animal species. For detail on these communities, please see the habitat narrative and maps for the New York - New Jersey Highlands.
VI. ECOLOGICAL SIGNIFICANCE/UNIQUENESS OF SITE: The Hudson River estuary is a productive and regionally significant estuary supporting important populations of fish and wildlife, as well as rare communities and plants. The mid-Hudson River estuary supports a variety of marine, brackish, and freshwater communities, incorporating 83 species of special emphasis, including the following federally and state-listed species. (Living resources and their habitats are dynamic; therefore, the ecological significance and species information presented here may not be complete or up-to-date. State and federal environmental agencies [see Appendix III for office contacts] should be consulted for additional information.)
Federally listed endangered
shortnose sturgeon (Acipenser brevirostrum)
Federally listed threatened
bald eagle (Haliaeetus leucocephalus)
Federal species of concern(1)
southern estuarine beggar-ticks (Bidens
bidentoides)
1Species of special concern listed here include former Category 2 candidates.
State-listed endangered
cylindrical-headed bulrush (Scirpus novae-angliae)
pygmyweed (Tillaea aquatica)
State-listed threatened
American bittern (Botaurus lentiginosus)
osprey (Pandion haliaetus)
State-listed special concern animals
banded sunfish (Enneacanthus obesus)
least bittern (Ixobrychus exilis)
State-listed rare plants
spongy arrowhead (Sagittaria calycina var.
spongiosa)
Bush's sedge (Carex bushii)
clustered sedge (Carex cumulata)
necklace sedge (Carex hormathodes)
weak stellate sedge (Carex seorsa)
slender crabgrass (Digitaria filiformis)
kidneyleaf mud-plantain (Heteranthera reniformis)
smooth bur-marigold (Bidens laevis)
pinweed (Lechea racemulosa)
yellow harlequin (Corydalis flavula)
redrooted flatsedge (Cyperus erythrorhizos)
salt marsh spikerush (Eleocharis halophila)
starwort (Callitriche terrestris)
slender knotweed (Polygonum tenue)
The open water and tidal wetlands in this 48 kilometers (30 miles) reach of the Hudson are regionally significant as spawning and nursery habitats and as a migratory pathway between the upper and lower estuary for anadromous and resident fish. Striped bass (Morone saxatilis) and Atlantic sturgeon (Acipenser oxyrhynchus) that are spawned in this area contribute greatly to the North Atlantic stock. The habitat contains many unusual features, including deep tidal river habitat that is a rare ecosystem type in the eastern United States, and an important winter foraging area for the federally listed threatened bald eagle (Haliaeetus leucocephalus). The numerous creeks and tidal brackish and freshwater marshes in this stretch serve as breeding, nursery, and migration corridors for fish and wildlife.
Focus areas (from south to north):
Annsville Creek is a tributary flowing south out of the Highlands into Peekskill Bay. The creek and mudflats are substantially cut off from Peekskill Bay and the Hudson River by the railroad. The creek has a moderate-sized area of brackish intertidal mudflats. Camp Smith Marsh is a small brackish tidal marsh with significant invasion by common reed. There are several occurrences of spongy arrowhead in the marsh and in the flats at the mouth of the creek.
Iona Marsh is located within Bear Mountain State Park, about 4.8 kilometers (3 miles) northwest of the town of Peekskill, on the west shore of the Hudson. The 109-hectare (270-acre) freshwater and brackish tidal marsh located to the west of Iona Island receives its freshwater inflows from Doodletown Brook, and is hydrologically connected with the Hudson through culverts under the railroad at both ends of Iona Island. The marsh is a breeding area for many marsh-nesting species of birds, including least bittern, green-backed heron (Butorides striatus), Canada goose (Branta canadensis), American black duck (Anas rubribes), wood duck (Aix sponsa), Virginia rail (Rallus limicola), sora (Porzana carolina), common moorhen (Gallinula chloropus), spotted sandpiper (Actitus macularia), belted kingfisher (Megaceryle alcyon), red-winged blackbird (Agellaius phoeniceus), swamp sparrow (Melospiza georgiana), and marsh wren (Cistothorus palustris). Shorebirds, herons, waterfowl, and osprey congregate on the marsh during both spring and fall migrations. Wintering waterfowl occur in small concentrations, including mergansers (Mergus spp.) and canvasback (Aythya valisineria) with smaller numbers of mallard (Anas platyrhynchos), Canada goose, and common goldeneye (Bucephala clangula). Spawning and nursery habitat for anadromous and resident freshwater fishes is provided by the many creek channels and shallow bay areas. Species found in the area include alewife (Alosa pseudoharengus), blueback herring (Alosa mediocris), white perch (Morone americana), striped bass, mummichog (Fundulus heteroclitus), and banded killifish (Fundulus diaphanus). The area supports a number of other resident species, including mink (Mustela vison), muskrat (Ondatra zibethica), northern water snake (Nerodia sipedon), snapping turtle (Chelydra serpentina), and green frog (Rana clamitans). Rare plants in the marsh and mudflats include pygmy-weed, spongy arrowhead, cylindrical-headed bulrush, starwort, and Long's bittercress (Cardamine longii); plants found along the riverbanks include redrooted flatsedge and salt marsh spikerush, and rare plants on Iona Island include Bush's sedge, slender knotweed, and pinweed. Bald eagles roost on the trees on the river side of Iona Island during the winter and feed in the adjacent deepwater segment of the river.
Hudson River mile 44-56 is a 19.3-kilometer (12-mile) river segment that includes all the fish and wildlife habitat of the main channel below mean low water. The area extends from Cornwall Bay to Peekskill Bay, and is relatively narrow, deep (up to 60 meters [200 feet]), and tortuous as the river passes through the Highlands area. This area is the largest continuous deepwater habitat segment in the river. During the springtime (high flow), it is the southern extent of fresh water; during the late summer and fall (low flow), the salt intrusion extends upstream above this habitat area. The river flow in this area is increased significantly over upstream areas because of the input of three major tributaries: Wappinger, Fishkill, and Moodna Creeks. Because of the rocky substrates, strong currents, and large volume of freshwater during the spring spawning time, this river segment is the primary striped bass spawning habitat in the Hudson, contributing significantly to the New York Bight and southern New England stock. This area is also a major portion of the spawning area for white perch and Atlantic sturgeon in the river, and a migratory pathway as well as a nursery area for a number of other anadromous fish including shortnose sturgeon. During summer flows this area is utilized by some of the marine and estuarine species including bluefish (Pomatomus saltatrix), bay anchovy (Anchoa mitchilli), silversides (Menidia spp.), hogchoker (Trinectes maculatus), and blue crab (Callinectes sapidus).
Bald eagles fish the upwelling, ice-free waters of this stretch of the river from December through March. Upwelling here is caused by the rapid rise of the river bottom in this zone, and the area is ice-free because of ice breaking activities for shipping lanes. Favorite winter food items for the bald eagles include resident fish such as the sunfish (Lepomis spp.), brown bullhead (Ameriurus nebulosus), and the exotic goldfish (Carrasius auratus), as well as anadromous fish such as juvenile and adult alewife and white perch. Concentrations of waterfowl feed and raft here in the winter, especially mergansers and canvasbacks, with lesser numbers of common goldeneye and Canada goose.
Con Hook Marsh is a small, brackish tidal marsh at river kilometer 79 (river mile 49) with a common reed-dominated marsh and an intertidal mudflat area with several rare plants, including cylindrical-headed bulrush, spongy arrowhead, necklace sedge, and pinweed. Con Hook Marsh is also a known concentration area for newly hatched Atlantic tomcod (Microgadus tomcod) and a wintering area for waterfowl, especially mergansers. There is another small marsh, Manitou Marsh, on the east shore just above the Bear Mountain Bridge. It is somewhat cut off from the river by the railroad, but has an outlet that provides tidal flow.
Constitution Marsh is a 161-hectare (400-acre) freshwater to brackish tidal marsh, dominated by narrow-leaved cattail emergent marsh; the remainder is intertidal mudflats and subtidal aquatic vegetation beds. It is located on the east side of the Hudson River south of the village of Cold Spring and is the largest undeveloped brackish tidal wetland on the Hudson River. Past discharges from an battery factory into Foundry Cove in Cold Spring have subjected this area to chemical pollution, chiefly cadmium and nickel in the north end of the marsh. A major contaminant remediation and wetland restoration project is now being completed in Foundry Cove. Aside from Foundry Cove, the surrounding area has minimal human disturbance, and a number of quality freshwater inflows makes this area an important breeding and feeding area for marsh-nesting birds, including least bittern, green-backed heron, Canada goose, mallard, wood duck, American black duck, sora, common moorhen, spotted sandpiper, belted kingfisher, marsh wren, fish crow (Corvus ossifragus), common yellowthroat (Geothylpis trichas), hooded warbler (Wilsonia citrina), red-winged blackbird, and swamp sparrow. The state-listed threatened osprey, waterfowl, herons, and shorebirds use this area during their spring and fall migrations. Overwintering waterfowl include mallard, American black duck, Canada goose, mergansers, and canvasback. The stream mouths and shallow water areas are spawning and nursery areas for anadromous fish including alewife, blueback herring, white perch, and striped bass, and for resident estuarine and freshwater species such as mummichogs, banded killifish, and largemouth bass. Snapping turtle take advantage of this forage base and are found in large numbers. Rare plants in the marsh include spongy arrowhead and smooth bur-marigold. Rare natural communities occurring on Constitution Island include a granite/gneiss cliff community and pitch pine-oak-heath rocky summit. Rare plants found on the island include Long's bittercress, clustered sedge, weak stellate sedge, yellow harlequin, slender crabgrass, pygmyweed, and taperleaf bugleweed (Lycopus rubellus).
Moodna Creek-Cornwall Bay is located north of the village of Cornwall on the west side of the Hudson River at river kilometer 92 (river mile 57). The habitat includes the creek from its mouth to the first dam just upstream of Route 32 at Orrs Mill, approximately 5.6 kilometers (3.5 miles). The tidally influenced portion of the creek, the lower 1.6 kilometer (1 mile), provides rare natural brackish communities, including tidal marsh and intertidal mudflats. One rare plant, spongy arrowhead, occurs in this area. There are extensive flats at the creek mouth and bay area that form a productive breeding habitat for least bittern, green-backed heron, Canada goose, mallard, wood duck, black duck, Virginia rail, spotted sandpiper, belted kingfisher, marsh wren, fish crow, common yellowthroat, hooded warbler, red-winged blackbird, downy woodpecker (Picoides pubescens), northern flicker (Colaptes auratus), eastern kingbird (Tyrannus tyrannus), and swamp sparrow. This area is a known migration corridor along the north slope of the Highlands for raptors, including bald eagles, which are consistently observed in the summer and winter. The area supports a diversity of other wildlife species, including raccoon (Procyon lotor), muskrat, white-tailed deer (Odocoileus virginianus), snapping turtle, green frog, and northern water snake. Moodna Creek is an important spawning area for anadromous fish, including alewife, blueback herring, rainbow smelt (Osmerus mordax), tomcod, white perch, and striped bass; the creek mouth provides nursery habitat. Various warmwater freshwater resident fish use the lower creek year-round, including largemouth bass (Micropterus salmoides), introduced bluegill (Lepomis macrochirus), indigenous pumpkinseed (Lepomis gibbosus), and brown bullhead. Marine species associate within this area when the salt front moves north in the dry season.
Fishkill Creek is on the east side of the Hudson in the city of Beacon at river kilometer 96 (river mile 60). The lower 2.4 kilometers (1.5 miles) of the creek from the mouth to the first dam is an important spawning area for anadromous fish. Between April and June it is extensively used by spawning alewife, blueback herring, and white perch. Tomcod spawn here in December and January. Marine fishes including bluefish, hogchoker, anchovy, and silversides are occasionally found here, and it is probably the northern extent of blue crab in the estuary. Resident freshwater species include largemouth bass, bluegill, brown bullhead, and goldfish. Both Fishkill and Wappinger Creeks are important overwintering areas for largemouth bass. Raptors migrating along the Highlands use this area as a major crossing of the Hudson Valley, and osprey are regularly sighted during the spring migration period. The creek also provides habitat for important resident furbearers and turtles, as well as feeding and resting areas for waterfowl. Invasion of the open water creek mouth area by water chestnut (Trapa natans) has reduced some of this area's habitat value; however, rare plant species such as northern estuarine beggar ticks (Bidens hyperborea), smooth bur-marigold, and heartleaf plantain (Plantago cordata) occur in the estuary area.
Wappinger Creek is a tidally influenced large warmwater perennial creek at river kilometer 108 (river mile 67). The first 3.2 kilometers (2 miles) runs from the mouth to the first dam in the village of Wappinger Falls, and serves as an important spawning area for anadromous fish including alewife, blueback herring, white perch, and tomcod. Most of the area is tidally influenced and contains a variety of habitat types, including freshwater tidal marsh and intertidal mudflats, aquatic beds, sandbars, and rocky shore. This area is the southernmost extent of sizable freshwater tidal marsh in the Hudson. The diversity of this riverine habitat provides favorable habitat for herons, waterfowl, furbearers, and turtles. Osprey congregate during the spring migration at the creek mouth where they take advantage of the abundant forage fish. Small concentrations of canvasback and other waterfowl species occur both north and south of Wappinger Creek in the winter. The area supports a full array of freshwater resident fish species, including largemouth bass, bluegill, pumpkinseed, red-breast sunfish (Leopomis auritus), and brown bullhead. The area has been extensively invaded by water chestnut, somewhat reducing habitat quality; however, a number of rare plant species are known to occur in the tidal estuary, including grassleaf arrowhead (Sagittaria graminea), spongy arrowhead, kidneyleaf mud-plantain, and southern estuarine beggar ticks. This area is within the reach of the river identified to be important for Atlantic sturgeon spawning.
Mine Point is located on the east shore of the Hudson River just south of Poughkeepsie at river kilometer 118 (river mile 74). The site contains a good occurrence of a limestone woodland community on steeply sloping limestone knobs, and supports an excellent occurrence of yellow harlequin, a rare plant.
Poughkeepsie Deepwater is another stretch of deepwater tidal river in the Hudson. This estuarine habitat is composed of a 22.5-kilometer (14-mile) stretch of the river formed by a large trench. Water depths start at 9 meters (30 feet) and increase to the bottom of the river where they exceed 38 meters (125 feet) in an area known as "Crum Elbow" at approximately river kilometer 129 (mile 80) in the Upper Hudson River Estuary. Denser brackish water is overlain by fresh water near the salt wedge, providing an environment that supports an assortment of marine and estuarine fish, including wintering habitat for shortnose sturgeon. Estuarine-dependent and marine species are found in this area, including silversides, bay anchovies, bluefish, weakfish (Cynoscion regalis), and hogchoker.
VII. THREATS AND SPECIAL PROBLEMS: All activities that degrade water quality in the mid- Hudson River estuary adversely affect the fish and wildlife that use this habitat for various life functions. Water pollution by toxic, chemical, or oil spills, excessive turbidity, sedimentation, and nonpoint source pollution degrade the quality and function of this habitat. Toxic contamination also carries with it long-term effects to the food chain through bioaccumulation and biomagnification and their possible effects on people. Habitat disturbance by human activities such as dredging and in-river and shoreside construction result in impaired water quality that may impede migrating anadromous fish trying to reach their spawning areas. This disturbance also impacts many of the other species using the estuary as a nursery area. Human disturbance from recreational activities such as boating, fishing, and hunting is also a threat.
Several major power plants occur in the mid-Hudson River estuary, including Lovett at river kilometer 67 (river mile 42), Indian Point at river kilometer 69 (river mile 43), and Roseton and Danskammer at river kilometer 107 (river mile 66). The use of fresh water, especially nonconsumptive use, can disturb the salt wedge dynamics, altering the salinity gradients in the river. The effect is twofold, removing fresh water from the watershed and, after it is used, discharging it artificially in a higher salinity zone. Such actions allow the salt front to migrate much higher in the estuary, which is most evident during the summers of drought years. The natural salinity regime is important to maintaining habitat function and species diversity. Operation of water intakes significantly impacts fish populations through impingement of adults and juveniles and entrainment of the critical egg and larval life stages. Another adverse impact can be attributed to discharge of thermally altered water into the river; temperature change of 10°C (17.8°F) over the ambient can affect critical life stages of many of the river's inhabitants. An equally pervasive concern is the lack of minimum freshwater flows in many of the tributaries, making many spawning and nursery habitat only marginal during low flow years. The net effect of dams on most of the tributaries is the removal of a great number of miles of suitable anadromous fish spawning habitat from the system. Transportation has had a major effect on the Hudson; railroad bed construction as early as the 1840's paralleled both banks of the river, crossing all tributaries and isolating many of the tidal marsh complexes. Maintenance and rebuilding of railroads, roads, and bridges along the Hudson could adversely impact wetlands, rare plants, fish, and wildlife. Herbicide use along roads and railroads could destroy adjacent rare plant populations. Nonpoint source pollution in the form of runoff is a constant concern. Dredging necessary to maintain a shipping channel is of grave concern as dredge material disposal options become limited; many former or proposed sites, especially deepwater sites, are not biologically suitable as dredge disposal sites. Deposition of dredged material on or adjacent to rare natural communities and plant populations is a threat.
Invasion by exotic plant species including Eurasian water-milfoil (Myriophyllum spicatum) in subtidal areas, water chestnut in subtidal areas and mudflats, and purple loosestrife (Lythrum salicaria) and common reed in emergent marsh areas is a continuing problem.
The zebra mussel (Dreissena polymorpha) is a recent invader of North American freshwater lakes and ponds; in the mid-Atlantic drainage, zebra mussels now inhabit the Mohawk River and the Hudson River from Albany to Haverstraw Bay. Zebra mussels displace native benthic species, greatly reduce the amount of available phytoplankton, and are responsible for drastic changes in water clarity. These filter-feeding bivalves are capable of significant filtration rates (the volume of water filtered by an individual mussel per unit of time) that reduce available water column food chain production. Phytoplankton and detritus are major food sources for lake and riverine food webs, and excessive removal of phytoplankton and detritus reduces the zooplankton species that feed upon them and can result in fisheries-related impacts. Zebra mussels tend to colonize on rocky substrate in shoal areas, directly impacting these habitats. Their filtering activity tends to increase water clarity; with the increased light penetration, benthic community structure can change dramatically. Zebra mussels outcompete native mussel species for food and space, leading to a decline in native mussel population numbers. An equally disturbing impact of the zebra mussel infestation is the fouling of raw water intake systems such as those for drinking water, electrical generation, or industrial use; controlling fouling is problematic, since biocides introduced into the system in mitigation efforts are themselves detrimental to the ecosystem. Zebra mussel infestation also impacts recreational water use, affecting boaters and marina operators. These mussels are readily transported in ballast and on boat hulls; precautions must be taken to help prevent the further spread of this invasive exotic species.
VIII. CONSERVATION RECOMMENDATIONS: Water quality improvement efforts need to continue throughout the estuary. Upgrading of sewage treatment facilities and control of point and nonpoint source pollution should be a major goal throughout the watershed. Water withdrawal activities must be guided by conservation policy that minimizes impacts by reducing the amount of water withdrawn. Conserving water resources has added benefit by reducing the water that must be treated by municipal treatment facilities. Dredging activities should consider spatial and temporal methods aimed at reducing potential impacts to the migrating fish populations and use of nursery areas. Only comprehensive planning that recognizes the habitat values of this area, balanced with an analysis of the impact to the habitat of individual proposals taken in the context of cumulative impacts, will result in balanced and effective protection of the watershed and the greater New York Bight ecosystem. Maintenance and rebuilding of railroads, roads, and bridges should avoid impacts to wetlands and rare communities and species. Improvements in tidal circulation, such as larger or additional culverts, should be incorporated into maintenance projects.
There is a great deal of pressure for marina construction on the tidal Hudson River. Such projects should only be approved if they do not have significant impacts on fish, wildlife, and rare communities and plants. Dredging of brackish and freshwater intertidal mudflats for access to marinas should be avoided.
Full restoration of the hydrologic continuum (wetlands and the river), especially increasing hydrologic connections under the existing railroad beds, and restoration of riparian corridors along the tributaries to the Hudson will increase available upland habitat, improve the quality of aquatic habitat in the tributaries, and reduce sediment and nutrient input into the Hudson.
The U.S. Army Corps of Engineers, in cooperation with the New York State Department of State and the New York State Department of Environmental Conservation, has a habitat restoration study and project underway in the Hudson River basin. This project should result in restoration of some areas affected by past dredging projects, including improving circulation to tidal marsh areas, control and removal of exotic species, and creation of additional marsh areas. This study identified fifteen high priority sites for restoration, including four sites in the mid-Hudson River estuary: Moodna Creek/Cornwall Bay, Iona Island Marsh, Camp Smith Marsh/Annsville Creek/Peekskill Bay, and Manitou Marsh. A more comprehensive restoration program for the Hudson Estuary, including the tributaries and watershed, should be conducted in concert with this restoration work. Riparian restoration projects along tributaries to the Hudson River are especially important to limit nutrient and sediment loading into the estuary. Further research and carefully monitored restoration of wetlands dominated by exotic and invasive plant species such as purple loosestrife, Eurasian water milfoil, water chestnut, and common reed are needed. The various agencies and environmental organizations working on the Hudson should continue to cooperate and focus on biodiversity.
The New York State Department of Environmental Conservation recently published an action plan for the Hudson River estuary that outlines priorities and actions needed for managing aquatic resources, preserving upland habitat, open space, and scenery, revitalizing the river-based economy through environmental protection, and promoting stewardship through partnership. Among the recommended actions are: increase monitoring of shad, striped bass, and sturgeon populations; standardize monitoring of fish entrainment and impingement at all power generation facilities to determine and regulate cumulative fisheries impacts; establish biocriteria for monitoring water quality in the Hudson; study the feasibility of restoring habitats at up to 15 locations; amend wetland regulations to more completely protect freshwater tidal wetlands; amend regulations to protect class C and D tributaries to the Hudson; conduct a biodiversity survey and recommend measures for protection; evaluate opportunities to transfer open space lands along the river with a target of 1,619 hectares (4,000 acres); promote the cleanup and appropriate reuse of abandoned and/or contaminated waterfront properties; and identify and quantify sources of contaminants of concern. These proposed actions should be fully supported by New York State and its partners.
IX. REFERENCES:
Bode, R.W., M.A. Novak, and L.E. Abele. 1993. 20-year trends in water quality of rivers and streams in New York State based on macroinvertebrate data 1972-1992. Executive report. Stream Biomonitoring Unit, New York State Department of Environmental Conservation, Albany, NY.
Buckley, E.J. and S.S. Ristich. 1976. Distribution of rooted vegetation in the estuarine marshes of the Hudson River. Boyce Thompson Institute for Plant Research, Inc., Ithaca, NY.
Green, D.M., S.E. Landsberger, S.B. Nack, D.Bunnell, and J.L. Forney, 1993. Abundance and winter distribution of Hudson River black bass. Hudson River Foundation, New York, NY.
Heimbuch, D., S. Cairns, D. Logan, S. Janicki, J. Seibel, D. Wade, M. Langan, N. Mehrotra. 1994. Distribution patterns of eight species of Hudson River fish. Coastal Environmental Services, Linthicum, MD.
Hudson River Valley Greenway Council. 1991. A Hudson River greenway: a report to Governor Cuomo and the New York State Legislature. New York State Office of General Service, Albany, NY.
Lawler, Matusky and Skelly Engineers. 1991. 1990 year class report for the Hudson River estuary monitoring program. For Consolidated Edison Co. of New York. Project no. 115-158.
Limburg, K.E., M.A. Moran, and W.H. McDowell. 1986. The Hudson River ecosystem. Springer series on environmental management, Springer-Verlag, Inc., New York, NY.
New York State Department of Environmental Conservation. 1996. The Hudson River Estuary management action plan. Hudson River Estuary Management Program, New Paltz, NY. 95 p.
New York State Department of Environmental Conservation and U.S. Department of Commerce/NOAA. 1993. Hudson River National Estuarine Research Reserve final management plan. Office of Ocean and Coastal Resource Management, Sanctuaries and Reserves Division, Washington, D.C.
New York State Department of Environmental Conservation and U.S. Fish and Wildlife Service. 1978. Hudson River fish and wildlife report and critical areas listing, Cortland, NY.
New York State Department of State. 1987. Hudson River significant coastal fish and wildlife habitats, a part of the New York State coastal management program. Narratives for Iona marsh, Hudson River mile 44-56, Constitution Marsh, Moodna Creek, Fishkill Creek, Wappinger Creek, and Poughkeepsie Deepwater habitat narratives and maps. New York State Department of State, Division of Coastal Resources and Waterfront Revitalization, Albany, NY.
New York Department of State and The Nature Conservancy. 1990. Hudson River significant tidal habitats: a guide to the functions, values and protection of the river's natural resources. New York State Department of State, Albany, NY.
Reschke, C. 1990. Ecological communities of New York State. New York Natural Heritage Program, New York Department of Environmental Conservation, Latham, NY.
Schmidt, R. E. and K. Limburg, 1989. Fishes spawning in non-tidal portions of Hudson River tributaries. Hudson River Foundation, New York, NY.
Smith, C. L. and T. R. Lake. 1990. Documentation of the Hudson River fish fauna. American Museum of Natural History. New York, NY.
Smith, C. L. 1985. The inland fishes of New York State. New York State, Department of Environmental Conservation, Albany, NY.
State of New York Conservation Department. 1936. A biological survey of the lower Hudson watershed. Supplemental to twenty-sixth annual report. Albany, NY.
U.S. Army Corps of Engineers. 1995. Hudson River habitat restoration, Hudson River Basin, New York: reconnaissance report. U.S. Army Corps of Engineers, New York District, New York, NY.
U.S. Department of Commerce, NOAA Strategic Assessments Branch. 1985. National estuarine inventory: data atlas, Volume I: physical and hydrologic characteristics. NOAA Office of Oceanography and Marine Assessments, Rockville, MD.
Weinstein, L.H. (ed.). 1977. An atlas of the biologic resources of the Hudson Estuary. Boyce Thompson Institute for Plant Research, Inc. Yonkers, NY.
List of Species of Special Emphasis
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