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Orconectes rusticus (rusty crayfish) has spread from its original range throughout much of northeastern North America. Invading rusty crayfish can completely replace native crayfish and impact other parts of the community through changes in consumption, disturbance, and other effects. Our main objectives were to document rusty crayfish distribution in streams of the upper Susquehanna River watershed, NY, and to determine the extent of changes in crayfish community composition since the last major survey. We sampled streams during 1999–2005 to describe the current distribution of crayfish species and to document short-term temporal changes. To determine long-term changes in species composition and distribution, we compared our data to museum specimen collection records. We found significant changes in the crayfish community; our surveys found 2 species not previously reported from the upper Susquehanna River watershed and failed to find 2 species previously reported. We also found that rusty crayfish are widespread in the watershed and continues to expand, while the ranges of native congeners are retracting.
Prior to this study, undocumented morphological variation in Lythrurus umbratilis (Redfin Shiner) has impaired identification of many samples of eastern populations of the species. Meristics, morphometrics, tuberculation, pigmentation, and nuptial male coloration of over 700 specimens of L. umbratilis were examined in order to assess patterns of geographic variation and species limits in the Ohio River basin. Principle component and spatial autocorrelation analyses of these data demonstrate that morphological variation in L. umbratilis is clinal along most of the length of the Ohio River basin. Specimens from eastern populations have less black in the dorsal fin of breeding males, have lower mean scale counts, and are more slender than western populations. The cline does not extend into central and northern Ohio, as populations have relatively high meristic counts and more robust males. These analyses suggest that recognition of an additional species in the Ohio River basin is not warranted at this time. The cline may reflect the influence of drainage evolution of the region, or even past gene flow with Lythrurus fasciolaris (Scarlet Shiner), a closely related species with a distribution parapatric to that of L. umbratilis.
Fish were sampled from the entire 34.4-km Bronx River each year from 2001 to 2005 inclusive, yielding a database of 4000 fish comprising 23 freshwater species and 22 estuarine species. These data were compared to the historic data from 1936–1998 as recorded in the New York State Department of Environmental Conservation's digital database, Albany, NY. Only 6 freshwater species reported in the historic data—Rhodeus sericeus (Bitterling), Salmo trutta (Brown Trout), Semotilus corporalis (Fallfish), Esox americanus vermiculatus (Grass Pickerel), Etheostoma nigrum (Johnny Darter), and Esox lucius (Northern Pike)—are no longer in the river. However, the original report of the presence of the Johnny Darter probably resulted from taxonomic confusion since this species has never been in the Hudson Valley, and we strongly believe that the report of the presence of grass pickerel is also the result of misidentification of the specimen for the same reason as given for the johnny darter. The report of the Brown Trout should be discounted since this species has been only taken in the Bronx River following a stocking event. We have found a breeding population of Brown Trout in the southern end of Davis Brook, but these have not yet traversed the multi-channel marsh area to enter the Bronx River proper. Therefore, only three previously reported species—Bitterling, Fallfish, and Northern Pike—are no longer in the river. Four spe cies—Fundulus diaphanus (Banded Killifish), Ameiurus nebulosus (Brown Bullhead), Apeltes quadracus (Fourspine Stick leback), and Micropterus dolomieu (Smallmouth Bass)—not reported in the historic database were part of our 2001–2005 freshwater collection. These discrepancies are explained, and on balance, it was determined that for the past 70 years, the Bronx River has been remarkably stable in terms of fish species and diversity. Examination of the estuarine portion of the river shows that it functions as an important nursery ground for many commercial and recreational fish harvested from New York waters.
The British Headquarters Map, circa 1782, provides a remarkable window onto the natural topography, hydrology, and land cover of Manhattan Island, NY, before extensive urbanization. Manhattan formerly hosted a rugged topography watered by over 108 km of streams and at least 21 ponds, flowing in and out of wetlands that covered nearly 10% of the island in the late 18th century. These features are largely representative of the landscape prior to European settlement. We used ecological features interpreted from the British Headquarters Map, and additional historical, ecological, and archeological information, to hypothesize about the ecosystem composition of the pre-European island. We suggest that 54 different ecological communities may have once been found on the island or in nearby waters, including chestnut-tulip tree forests, Hempstead Plains grasslands, freshwater and tidal marshes, hardwood swamps, peatlands, rocky headwater streams, coastal-plain ponds, eelgrass meadows, and culturally derived ecosystems, such as Native American village sites and fields. This former ecosystem mosaic, consisting of over 99% natural areas, stands in sharp contrast to the 21st-century state of the island in which only 3% of its area is dedicated to ecological management.
This study examines the ecology of Rangifer tarandus caribou (woodland caribou) in the Naosap range in west-central Manitoba, Canada. This population is considered to be of high conservation concern because of potential resource-development impacts; therefore, baseline data are required to guide and evaluate the management of this species in this area. Radio-telemetry data were collected every two weeks from February 1998 to April 2001 and used in combination with forest-inventory data to evaluate habitat selection, site fidelity, movement, and grouping patterns. In both summer and winter, selected habitats were mature upland spruce and pine forests, as well as treed muskeg. Hardwood forests were least selected at all scales. Mature coniferous forest was preferred over immature coniferous forests in a pair-wise comparison in winter, but not in summer. Home-range sizes were within expected ranges of variation. Animals used distinct areas in summer and winter, showing broad fidelity to seasonal ranges. However, small shifts in the core areas were observed, particularly in winter. Movement rates and grouping behavior were typical of other caribou. Habitats used in winter were common in the study area, but the ability of the animals to disperse to alternate winter areas is not known. Management efforts could focus on protecting known calving and winter-use areas, and regenerating coniferous forests after logging, which is consistent with regional forest-management objectives.
Sixteen Acer rubrum (red maple)-dominated wetlands in three hydrogeomorphic settings (depressional, riverine, seepage slope) were sampled in southeastern Massachusetts. Quantitative data of vegetation from five strata were compared with soil-chemistry measurements using detrended correspondence analysis (DCA) to determine if hydrogeomorphic (HGM) setting was related to species composition. Although all sampled wetlands were dominated or co-dominated by red maple, DCA-differentiated stands according to HGM setting, i.e., riverine flood-plain wetlands separated from depressional (kettle) wetlands and slope wetlands on the DCA ordination. Further, species richness was lowest in depressional wetlands and highest in riverine wetlands, reflecting differences in soil chemistry and soil type, ultimately determined by hydrogeomorphic setting. Depressional swamps overwhelmingly dominated by red maple and those with Chamaecyparis thyoides (Atlantic white cedar [AWC]) were very similar in understory composition, soil chemistry and type, and ordination position, suggesting that many of the red maple depressions were probably once AWC swamps. Post-colonial forest-management practices such as repeated cutting of stands, fire suppression, draining for conversion to cranberry bog, and subsequent abandonment have degraded and fragmented AWC swamps throughout southeastern Massachusetts and extensively reduced their areal extent. However, recent abandonments of cranberry bogs have provided opportunities for restoring AWC wetlands to a portion of their original habitat.
Studies of forested rural watersheds provide estimates of background contamination for comparison with streams and rivers in other settings. We performed a landscape analysis and measured major dissolved ions and benthic macroinvertebrates for a small rural watershed in Albany County, NY, to determine spatial variation in water quality. An estimated 73% of the surface cover is post-agricultural forest, with only 2.3% of the watershed covered by roads and other impervious surfaces. Although water quality was consistently high in most of the creek, we detected three relatively distinct zones separated by impoundments; zonation was most apparent in relative concentrations of major ions, less so with benthic macroinvertebrate community similarity. At ten sample stations, buffer size, measured as upstream land cover and distance to nearest road, did not correlate well with chemical water quality indicators. In particular, we found the highest levels of chloride, indicative of road-salt contamination, in areas of maximum forest buffer. Small feeder creeks that drain nearby roads may function as “leaks” in otherwise well-buffered watersheds with low road densities.
Ambystoma texanum (Small-mouthed Salamander) breeds primarily in temporary wetlands, and while natural history studies have suggested a minimum larval period of about 2 mo, it is not clear how hydroperiod (the length of time that a temporary wetland holds water) influences populations. I conducted a mesocosm experiment to investigate the effects of hydroperiod on the completion of metamorphosis, as well as age and size at metamorphosis. I used hydroperiods of 50, 75, and 100 d, and a non-drying treatment as a control. Survival to the end of each hydroperiod was consistent among all groups, but no individuals completed metamorphosis in the 50-d treatment. The proportion of individuals completing metamorphosis increased with longer hydroperiods, as did the age at metamorphosis. The size at metamorphosis, however, was not affected by the length of the hydroperiod. My results show that a minimum hydroperiod of 2.5 mo is necessary for populations of Small-mouthed Salamander. Maintenance of natural hydroperiods in wetlands under the threat of development is a critical consideration for the long-term persistence of Small-mouthed Salamander populations.
We report one instance of conspecific nest reuse by Hylocichla mustelina (Wood Thrush) within the same breeding season, two instances of conspecific nest reuse in subsequent breeding seasons, and two instances of Wood Thrushes reusing nests originally constructed by Pheucticus ludovicianus (Rose-breasted Grosbeaks) during a three-year study in Ontario. Rates of nest reuse were higher than previously reported for Wood Thrush, with conspecific nest reuse accounting for 8–12% of the observed nesting activity, and interspecific nest reuse accounting for 8–9%. Nest reuse occurred following periods of colder minimum temperatures or greater precipitation than in other years. We suggest that instances of nest reuse within and between breeding seasons may occur in response to time or energy constraints on females resulting from unusual weather conditions. Documenting instances of nest reuse behaviour contributes to our understanding of some of the constraints experienced during breeding and may shed light on factors affecting annual reproductive success.
We conducted 11 call-broadcast surveys at one location in each of four wetlands, and detected an Ixobrychus exilis (Least Bittern) on only 9 of the 44 (20%) surveys, while the observer was located on average 50.1 m ± 19.7 SD (range = 25–75 m, n = 11 nests) from at least one active bittern nest during each survey. For 8 of 9 (89%) detections, at least one bittern was already vocalizing at the beginning of the survey, before the Least Bittern call was played. We show that it is possible for this species to remain undetected with the use of call-broadcasts that are less than 30 seconds, even though the species may be nesting as close as 25 m to the location from which the calls are broadcasted. We suggest that systematic nest searches are more reliable than call-broadcast surveys for detecting nesting Least Bitterns.
Impervious surface area (ISA) has emerged as a key indicator to explain and predict ecosystem health in relationship to watershed development. In this study, we extracted the information of ISA for the state of Rhode Island using 1-m spatial resolution true-color digital orthophotography data. We employed an object-oriented algorithm of multiple-agent segmentation and classification (MASC) that we developed for ISA information extraction. The result indicates that, as of 2004, 10% of the state land has been covered by ISA. The major population centers and historical cities, such as Providence, Woonsocket, and Newport, have ISA over 30%. The heavily settled suburban communities have ISA between 10 and 30%. Only 17 out of 39 towns in the state have less than 10% ISA. The average ISA for the coastal towns is 14%. Because most stream-quality indicators are predicted to decline when watershed ISA exceeds 10%, the results from this study serve as an alarming indicator for managing the state's watershed and coastal ecosystems. The tested MASC model could be extended to coastal Massachusetts and Connecticut to provide a more comprehensive indication of the impacts of human-induced land-cover change on southern New England's coast.
During September 2004 and June 2005, the Virginia Institute of Marine Science (VIMS) Juvenile Fish and Blue Crab Trawl Survey collected specimens of three warmwater fish species uncommon to Chesapeake Bay. Captures of Trachinocephalus myops (Snakefish), Citharichthys macrops (Spotted Whiff), and Mullus auratus (Red Goatfish) are the first substantiated records for these species from Chesapeake Bay. These captures also represent extensions in the documented geographic ranges of Snakefish and Spotted Whiff. Occurrences of multiple species heretofore rarely encountered in Chesapeake Bay warrant further attention in view of concerns regarding climate change and its effect on local marine faunas.