Hudson River Fishes and their Environment

<em>Abstract.</em>—Hudson riverine and coastal marshes provide a paleoecological archive consisting of information on climate and land use at both the local and watershed scales. The timing of formation of these marshes is documented using accelerator mass spectrometry (AMS) ¹⁴C dating of identified plant macrofossils in basal marsh organic sediments. While the Staten Island marsh is oldest and dates to 11,000 years before present (BP), Piermont, Iona, and Croton marshes date to the mid-Holocene, and the Jamaica Bay marshes formed most recently. Pollen and spores, charcoal, and plant macrofossils in the marsh sediments document marked climatic shifts as well as anthropogenic impact in the region. Assessment of the inorganic and organic content of the sediments in the marshes reveals a pattern of decreasing inorganic supply with the arrival of the Europeans, possibly due to the construction of numerous Hudson River tributary dams. Piermont Marsh, because of its sensitive location in the Hudson River, records droughts and wet intervals through species which have specific salinity affinities. Throughout the marsh records, the ragweed <em>Ambrosia </em>pollen rise marks the anthropogenic impact at the landscape scale. The recorded changes in hydrology and salinity that occurred throughout the centuries and millennia would have had profound effects throughout the food web and estuarine ecosystem. Fish populations would have been affected by changes in the food supply due to shifts in runoff affecting turbidity and light penetration in the river. Local vegetation changes within marshes may also have affected juvenile fish populations.

Hudson River Fishes and their Environment

<em>Abstract.</em>—Using a combination of data sources and historic or contemporary accounts, we describe and document changes in the Hudson River watershed’s population size, agricultural and forested land uses, and the construction of dams, largely since the time of European colonization. Population within the watershed has grown from 230,000 at the time of the first census in 1790 to around 5 million today (not including parts of those boroughs of New York City outside the watershed, such as Queens). The watershed was almost entirely forested in 1609, with minor amounts of Indian agriculture. By 1880, approximately 68% of the watershed was farmland, but as soil productivity declined and industry created other jobs, much cleared land gradually reverted to secondary forest. Most land not in agriculture was forested and exploited first for lumber and tanbark and, later on, pulpwood for paper. The tanning industry existed from the 1700s, but reached its height in the mid-1800s, collapsing from a combination of resource (hemlock) exhaustion and market forces. Finally, available records list nearly 800 dams, ranging from 0.6 m to 213 m (Ashokan Reservoir) in height and with maximum storage of 1.07 km³ (Sacandaga Reservoir), that were constructed from the early 18^th century until 1993. The environmental legacies of these changes include effects on hydrology, soils, vegetation, biogeochemical cycling, sediment loading, and ecological relationships

Hudson River Fishes and their Environment

<em>Abstract.</em>—Our objective was to determine if dispersal of age-2+ striped bass out of the Hudson River was affected by cohort abundance or stock size. We evaluated dispersal using the location of tagged age-2+ striped bass (in or outside of the Hudson River) and distance from the mouth of the Hudson River when they were recaptured by anglers. The proportion of age-2+ striped bass recaptured outside the Hudson River annually during May was significantly and positively correlated with cohort abundance (<em>r </em>= 0.978, <EM>P </EM>< 0.001), but not with stock size <em>(r </em>= 0.739, <EM>P </EM>= 0.094). The maximum distance at which an age-2+ striped bass was recaptured outside the Hudson River annually was also significantly and positively correlated with cohort abundance (<em>r </em>= 0.869, <EM>P </EM>< 0.025). Therefore, it appears that dispersal of age-2+ striped bass out of the Hudson River was densitydependent and due to cohort abundance.

Hudson River Fishes and their Environment

<em>Abstract.</em>—Our objectives were to determine if striped bass <em>Morone saxatilis </em>larvae were present in the East River and if so, could they have come from the Hudson River. To meet the first objective, we examined entrainment data collected at the Charles Poletti Power Plant (Poletti) during the years 1999 through 2002. To meet the second objective, we examined the simulated release of 168,000 neutrally buoyant, passive particles in the lower Hudson River Estuary, using a particle-tracking model that was linked to an estuarine circulation model. We also compared the abundance of striped bass post-yolk-sac larvae (PYSL) collected in the East River at Poletti with the abundance of striped bass PYSL collected in the Battery region of the lower Hudson River Estuary and the abundance of striped bass PYSL in the Battery region with freshwater flow in the estuary. Striped bass PYSL were collected by entrainment sampling in the East River at Poletti every year from 1999 through 2002. The striped bass PYSL in the East River probably came from the Hudson River Estuary because the median probability that neutrally buoyant, passive particles would be transported from the lower Hudson River Estuary to the upper East River and western Long Island Sound was 0.12, with a median transport time of 2 d, and because the mean density of striped bass PYSL was highest at Poletti and in the Battery region during the same year. The abundance of striped bass PYSL in the Battery region was higher when freshwater flow during May and early June was higher.

Hudson River Fishes and their Environment

<em>Abstract.</em>—Pelagic fish abundance and distribution was estimated acoustically at Bowline and Indian Point power plants on the Hudson River, New York, during July, August, and September 1996, in a study designed to determine size-specific spatial and temporal fish abundance and distribution with respect to environmental variables (i.e., photoperiod, depth strata, field). August yielded the greatest (<EM>P </EM>< 0.05) mean density of fish at both power plants. Fish were concentrated in Bowline’s near-field (lagoon) region, thus increasing the potential for deleterious impingement and entrainment effects there. For all size classes, mean fish density was greatest during darkness at both power plants. Generally, the two power plants exhibited similar trends in mean fish abundance with respect to water depth and photoperiod. During July and August mean fish density was significantly higher between 1.5 and 4.5 m (depth strata one) of depth at both power plants. Bowline’s mean fish density was greater under near-field, shallow depth (depth strata one) darkness during July and August. Bowline’s isolated and bathymetrically complex near-field lagoon concentrated pelagic fish compared to the river proper. Hydroacoustics were useful in providing a detailed map of fish distribution relative to each power plant over the course of a few days each month. Hydroacoustic monitoring could mitigate negative effects to pelagic fish at existing and proposed power plants, through sighting of power plant water intake structures or by providing a biological basis for modified production cycles.

Hudson River Fishes and their Environment

<em>Abstract.</em>—Our objectives were to examine the distribution and abundance of bay anchovy <em>Anchoa mitchilli </em>eggs and larvae in the Hudson River and nearby waterways and to determine if past conditional mortality rate (CMR) estimates for bay anchovy entrained at Hudson River power plants may be substantially biased because they were based solely on sampling in the Hudson River. We addressed these objectives by comparing ichthyoplankton samples collected in the Hudson River with those collected in New York Harbor, the East River, and Long Island Sound using the same gear during 2002. Bay anchovy eggs were collected from late April through the end of sampling in the Hudson River (early October) and through the end of sampling in nearby waterways (late July). Bay anchovy larvae were collected from early June through end of sampling in both the Hudson River and nearby waterways. The highest densities of bay anchovy eggs and larvae in nearby waterways were about 13 and 14 times greater, respectively, than the highest densities in the lower Hudson River. The peak standing crops of bay anchovy eggs and larvae in nearby waterways were about eight times larger than those in the Hudson River. Therefore, past CMR estimates for bay anchovy entrained at Hudson River power plants may be substantially biased if the bay anchovy eggs and larvae collected in the Hudson River and nearby waterways during 2002 belonged to one population, as it appears they did, and 2002 was representative of other years.

Hudson River Fishes and their Environment

<em>Abstract.</em>—The Hudson River Estuary (defined here as the Hudson River drainage and New York Harbor) is home to a large and diverse ichthyofauna. Estimates of species richness reflect both their geographic boundaries and time periods. The most complete estimate is for the Hudson River drainage north of the southern tip of Manhattan, where, as of 2005, 212 fish species have been recorded. This includes 11 new forms not reported in the most recently published tally (1990). We categorize the fishes of the Hudson River drainage as derived from 12 zoogeographic or anthropogenic sources (including species for which we make no judgment [<em>n </em>= 26]), the largest contributions from which include temperate marine strays (<em>n </em>= 65), introduced species (<em>n </em>= 28), and freshwater species that survived Pleistocene glaciations in Atlantic coastal refugia (<em>n </em>= 21). Additional species appear to have invaded from the Mississippi refugia, some naturally (<em>n </em>= 11) and some later, via canals (<em>n </em>= 11). Only ten diadromous fishes occur in the estuary, but many of these are, or have been, commercially and recreationally important (e.g., Atlantic sturgeon <em>Acipenser oxyrinchus</em>, American shad <em>Alosa sapidissima</em>, and striped bass <em>Morone saxatilis</em>). Extremely high seasonal temperature changes in the main-channel Hudson River foster a seasonally dynamic ichthyofauna with relatively few species occurring year round. However, the small number of resident estuarine fishes (<em>n </em>= 8) often occur in high abundances. Species richness peaks between June and September and reaches a minimum in winter. Long-term data indicate that although species richness has increased with the additions of new species, diversity is decreasing because of the decrease in population size of certain species, especially native cyprinids. The Hudson estuary hosts a population of one federally endangered species, shortnose sturgeon <em>Acipenser brevirostrum</em>, which is flourishing. Only one species, the anadromous rainbow smelt <em>Osmerus mordax </em>appears to have become extirpated in the Hudson Estuary.

Hudson River Fishes and their Environment

<em>Abstract.</em>—The Hudson River Estuary can be classified as a drowned river valley, partially mixed, tidally dominated estuary. Originally, it had a fjord-like morphology as a result of glacial scour which filled in over the past 3,000 years with river sediments. The hydrodynamics of the estuary are best described by the drivers of circulation, including the upstream river inflows, the oceanographic conditions at the downstream end, and meteorological conditions at the water surface and the response of the waters to these drivers in terms of tides and surges, currents, temperature, and salinity. Freshwater inflow is predominantly from the Mohawk and Upper Hudson rivers at Troy (average flow = 400 m³/s, highest in April, lowest in August). At the downstream end at the Battery the dominant tidal constituent is the semidiurnal, principal lunar constituent (the M₂ tide), with an evident spring/neap cycle. The amplitude of the tide is highest at the Battery (67 cm), lower at West Point (38 cm), and higher again at Albany (69 cm), a function of friction, geometry, and wave reflection. Meteorological events can also raise the water surface elevation at the downstream end and propagate into the estuary. Freshwater pulses can raise the water level at the upstream end and propagate downstream. Tidal flows are typically about an order of magnitude greater than net flows. The typical tidal excursion in the Hudson River Estuary is 5–10 km, but it can be as high as 20 km. Temperature varies seasonally in response to atmospheric heating and cooling with a typical August maximum of 25°C and January-February minimum of 1°C. Power plants cause local heating. The salinity intrusion varies with the tide and amount of upstream freshwater input. The location of the salt front is between Yonkers and Tappan Zee in the spring and just south of Poughkeepsie in the summer. Vertical salinity stratification exists in the area of salt intrusion setting up an estuarine circulation. The effect of wind is limited due to a prevailing wind direction perpendicular to the main axis and the presence of cliffs and hills. Dispersive processes include shear dispersion and tidal trapping, resulting in an overall longitudinal dispersion coefficient of 3–270 m²/s. The residence or flushing time in the freshwater reach is less than 40 d in the spring and about 200 d in the summer. In the area of salt intrusion, it is about 8 d.

Hudson River Fishes and their Environment

<em>Abstract.</em>—Recreational fishing throughout the Hudson River estuary from the federal dam at Troy (river kilometer [rkm] 243) to the George Washington Bridge (rkm 19) was investigated during March 2001 through March 2002. Aerial counting surveys and angler interviews at nearly 200 access points were used to estimate fishing pressure, catch and harvest, catch rates, and various angler attributes. Fishing pressure for the mid-March through November period was estimated at 446,621 angler-hours. Most effort occurred in the late spring by anglers north of the Bear Mountain Bridge (rkm 74). Angling from boats comprised 72.6% of total effort. The total number of fish caught and harvested was estimated at 212,426 and 44,479 individuals, respectively, representing 31 species plus blue crab <em>Callinectes sapidus</em>. Most of the total catch was by boat anglers, although over the entire survey period shore anglers harvested the most fish. In sequence, striped bass <em>Morone saxatilis</em>, river herring <em>Alosa </em>spp., and white perch <em>M. americana </em>were the three most abundant species caught, whereas river herring, white perch, blue crab, and striped bass formed most of the harvest. Catch per unit effort (CPUE) and harvest per unit effort (HPUE) of shore anglers (0.69 fish/h and 0.22 fish/h) were higher than that of boat anglers (0.44 fish/h and 0.02 fish/h). Most anglers throughout spring sought striped bass, whereas during summer and fall boat anglers sought primarily black bass <em>Micropterus </em>spp., with much effort occurring during tournaments. Shore anglers were less focused and sought a broader variety of species. As a group, anglers fishing south of the Bear Mountain Bridge were less aware of fish consumption advisories due to contaminants than anglers fishing elsewhere in the estuary.