Relations of Environmental Factors with Mussel-Species Richness in the Neversink River, New York
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1 Prepared in cooperation with The Nature Conservancy and Sullivan County Division of Planning and Environmental Management Relations of Environmental Factors with Mussel-Species Richness in the Neversink River, New York Significant Findings • A 6-year study of mussel communities and their habitat in the Neversink River basin in southeastern New York found that the principal factors apparently affecting mussel-species richness were site (reach) elevation, drainage-area size, channel width, bottom- material composition, water velocity, shear stress at bankfull discharge, and water quality (acid- neutralizing capacity (ANC) and concentrations of calcium, phosphorus, and sulfate). Together these 10 factors explained as much as 94 percent of the variability in mussel-species richness across the watershed. Swollen wedgemussel (Alasmidonta varicosa) from the Neversink River. • The number of species in mussel communities throughout the basin typically increases in a downstream progression from zero or one species in upstream sites to as many as six species in downstream sites. • A recently removed dam in the lower part of the river may have confined populations of two rare mussel species to lower reaches of the Neversink River; its removal in 2004 could allow those species to populate additional reaches in the upper basin. U.S. Department of the Interior Printed on recycled paper Open-File Report 2007–1283 U.S. Geological Survey March 2008 2 Introduction flow patterns have recently been (richness) were quantified through 2-hour proposed by TNC and could benefit snorkeling searches at 28 sites during the Declines in the distribution, the established mussel populations summer of 1997; of these, 17 were on abundance, and diversity of freshwater- and aquatic communities. The ability the main stem and 11 were on tributaries. mussel species (family Unionidae1) have to protect mussel populations and the Habitat and hydraulic features at each been reported worldwide (Bogan, 1993; potential to increase mussel richness study site were measured using point- Strayer and Jirka, 1997). The principal in the Neversink River is unknown, and-transect methods modified slightly causes of the observed declines are however, because the environmental from those presented in Meador and difficult to confirm, however, because factors that affect the seven mussel others (1993). Water depth, substrate only a few of the many factors that affect species are poorly defined, and the types, and water velocity were measured mussel-species populations have been distribution of mussel beds is patchy and at five to seven equally spaced points identified (Strayer and Ralley, 1993; thus difficult to quantify. across each transect and at the thalweg, Strayer, 1999; Baldigo and others, 2003; In 1997, the U.S. Geological and bank and riparian characteristics Strayer and others, 2006). Survey, in cooperation with TNC, began were measured or visually estimated at The Neversink River, which a 6-year study along the Neversink both ends of each transect. Water samples drains the Catskill Mountains in River and its tributaries to (1) document were collected at the same time from southeastern New York (fig. 1), contains the current distribution of each mussel single samples collected under base-flow seven species of mussels (Strayer and species, (2) assess environmental factors conditions and analyzed for acid- Ralley, 1991; Strayer and Jirka, 1997). in relation to mussel-species richness neutralizing capacity, and concentrations Populations of the endangered dwarf and distribution, and (3) identify the of calcium, phosphorus, sulfate, and 13 wedgemussel (Alasmidonta heterodon) factors that most strongly affect mussel other constituents. and the threatened swollen wedgemussel populations and develop an equation Mussel-transect surveys were done (Alasmidonta varicosa) coexist with other that relates environmental factors to in 2001 and 2002 at the 28 sites studied unionid mussels in the Neversink River mussel-species richness. This report during 1997 and at 4 additional main- (Strayer and Ralley, 1991, 1993; Baldigo (a) summarizes the methods used to stem sites. These surveys counted the and others, 2003). Dwarf wedgemussel quantify or qualify environmental number of each mussel species through populations had previously been found factors and mussel-species distribution snorkel surveys, measured wetted- only downstream from the site of an and abundance, (b) presents a list channel widths and water velocities, abandoned dam in the lower part of the of environmental factors that were documented the bankfull indicators, river at Cuddebackville (fig. 1), and correlated with mussel-species richness, and estimated bankfull width, depth, swollen wedgemussels were only found and (c) offers an empirical model to and cross-sectional area within three in the lower and middle reaches of the predict richness of mussel species bank-to-bank transects across each river. The limited distribution of these in benthic communities throughout study site. Channel-slope measurements two species suggests that they may be the basin. from longitudinal bed-elevation surveys susceptible to local extinctions. were used with bankfull dimensions The distribution of mussel to calculate mean water velocities and populations can be limited by shear stresses for each transect at high impoundments. Mussel larvae develop Methods bankfull-discharge stages for 21 of the in species-specific host fish; thus, 32 study sites. Surveys were conducted during impoundments that restrict passage of The relations between mussel- the summers of 1997–2002 on the these host fish also restrict the extent species richness and water chemistry, Neversink River and its tributaries to of mussels. The Neversink River is habitat features, bankfull-channel document mussel communities, water impounded by the Neversink Reservoir geometry, and basin characteristics (such quality, habitat characteristics, and [241 square kilometers (km2)], a as elevation and size of drainage area) bankfull discharge and geomorphology major source of drinking water for were assessed through simple, multiple, at 28 sites ranging in length from the City of New York, and was also and quantile regression analyses. Ten 100 meters (m) (for habitat assessments) impounded 50 km downstream by the variables (site elevation, drainage-area to 600 m (for geomorphology surveys). Cuddebackville Dam until 2004, when size, mean channel width, amount of sand Habitat characteristics and bankfull the latter was removed by The Nature as a percentage of streambed material, discharge were measured at least once Conservancy (TNC) and the U.S. Army water velocity, shear stress, ANC, and at all sites, whereas complete bankfull Corps of Engineers to improve fish concentrations of calcium, phosphorus, geomorphology surveys were done passage. The removal of this dam has and sulfate) were identified as important provided previously unavailable habitat at only 21 main-stem sites. Sampling to mussel-species richness. The number for diadromous and other fish species methods for each environmental factor of data points used to assess the relations that act as hosts for rare mussel species. and mussel community are summarized of mussel-species richness with each of In addition, releases from the Neversink below and provided in greater detail by the ten factors typically varied between Reservoir that mimic the river’s original Baldigo and others (2002, 2003). 21 and 32 because of the different The number of each mussel species number of sites sampled for each survey 1 Words in boldface are explained in the glossary collected per hour (relative abundance) and ranged as high as 41 when transect on page 6. and the number of mussel species data from 21 sites were used to assess 3 er NY VT k Riv ersin r ev Rive N ink h s Catskill State Park nc ever ra h N MA t B nc Neversink Basin es ra W B st PA CT Ea 74°25' 41°55'0"N nv17 41°55' NJ nv16 nv12 74°45' nv15 41°52'30" nv14 Neversink nv13 Reservoir tr11 nv11 nv10 tr10 nv09 tr09 nv08 r ve tr07 i tr05 R tr08 k n i s tr06 er 74°45' v Ne nv07 41°32'30" tr04 tr02 41°30' tr03 74°22'30" nv06 Cuddebackville Dam nv05 r e v nv04 i R tr01 k nv03 in rs ve Ne nv02 nv01 0 2 4 6 8 10 MILES 0 2 4 6 8 10 KILOMETERS Base from U.S. Geological Survey digital data, 1:100,000, 1983, Universal Transverse Mercator Projection, Zone 18 Mussel species (picture at site indicates presence of species) EXPLANATION Dwarf wedgemussel (Alasmidonta heterodon) Sample site Alewife floater (Anodonta implicata) Triangle floater (Alasmidonta undulata) nv Neversink River reach Swollen wedgemussel (Alasmidonta varicosa) tr Tributary to the Neversink River Creeper (Strophitus undulatus) Absence of mussel-species bar Eastern elliptio (Elliptio complanata) indicates no mussels found. Eastern floater (Pyganodon cataracta) Figure 1. Location and number of mussel species collected during mussel surveys at 28 sites of the Neversink River basin in southeast New York, June–August 1997. 4 Biologists conducting timed snorkel surveys for mussels in the Neversink River. relations with velocity and shear stress. no mussels were found in 7 of the 11 located between the Cuddebackville Dam Separate equations describing the tributaries, nor in the 5 most upstream and site nv10 (fig. 1). maximum species richness, as a function of the 17 main-stem sites (fig. 1). The Relative-abundance data indicate of each variable, were standardized to most widely distributed species in the that the eastern elliptio was the most maximum values of 1. Averaged together, basin was the eastern elliptio (Elliptio abundant mussel species at nearly all these metrics form an unweighted complanata), which is tolerant of a study sites (fig. 2). Relative abundance index capable of predicting mussel- wide range of environmental conditions increased downstream and was generally species richness from similar data and habitat disturbances (Strayer and greatest at main-stem sites in the lower collected at other sites throughout the Jirka, 1997). It was the only species at basin; the primary exception to this Neversink River.