Time filter

Source Type

Bedford, NH, United States

Adams A.M.,Ben - Gurion University of the Negev | McGuire L.P.,Texas Tech University | Hooton L.A.,Normandeau Associates Inc. | Brock Fenton M.,University of Western Ontario
Canadian Journal of Zoology | Year: 2015

Passive acoustic monitoring is a common tool used for monitoring bat activity levels. Identifying periods and locations of peak levels provides insight into bat ecology and has important management implications. One limitation of passive acoustic monitoring is the relative nature of the data, often relying on subjective interpretation of descriptive terminology such as “higher” or “lower”. We propose the use of percentile thresholds (PTs) for objectively identifying peak activity. By compiling a reference data set, it is possible to define percentiles of the observed activity levels and these percentiles can provide objective thresholds for comparing activity levels. We used acoustic recordings from sites in Canada and calculated PTs based on the distribution of the number of calls per hour across all nights and sites for three species of bat. Given species ecologies (e.g., hibernating, migrating), we were able to use PTs to objectively identify peak activity levels on a species-specific basis. Percentile thresholds are also a replicable method of describing within-night activity by evaluating species-specific activity patterns and important times of night. Our analyses and examples represent a proof of concept. The next step is to move towards a standardized distribution to generate PTs. Creating a public repository of acoustic data sets to evaluate activity of a species in the context of its entire range would allow us to standardize terms such as “high” activity in an objective manner. © 2015, National Research Council of Canada.All rights reserved. Source

Stonedahl S.H.,Northwestern University | Stonedahl S.H.,Davenport University | Harvey J.W.,U.S. Geological Survey | Detty J.,U.S. Geological Survey | And 3 more authors.
Water Resources Research | Year: 2012

Improved predictions of hyporheic exchange based on easily measured physical variables are needed to improve assessment of solute transport and reaction processes in watersheds. Here we compare physically based model predictions for an Indiana stream with stream tracer results interpreted using the Transient Storage Model (TSM). We parameterized the physically based, Multiscale Model (MSM) of stream-groundwater interactions with measured stream planform and discharge, stream velocity, streambed hydraulic conductivity and porosity, and topography of the streambed at distinct spatial scales (i.e., ripple, bar, and reach scales). We predicted hyporheic exchange fluxes and hyporheic residence times using the MSM. A Continuous Time Random Walk (CTRW) model was used to convert the MSM output into predictions of in stream solute transport, which we compared with field observations and TSM parameters obtained by fitting solute transport data. MSM simulations indicated that surface-subsurface exchange through smaller topographic features such as ripples was much faster than exchange through larger topographic features such as bars. However, hyporheic exchange varies nonlinearly with groundwater discharge owing to interactions between flows induced at different topographic scales. MSM simulations showed that groundwater discharge significantly decreased both the volume of water entering the subsurface and the time it spent in the subsurface. The MSM also characterized longer timescales of exchange than were observed by the tracer-injection approach. The tracer data, and corresponding TSM fits, were limited by tracer measurement sensitivity and uncertainty in estimates of background tracer concentrations. Our results indicate that rates and patterns of hyporheic exchange are strongly influenced by a continuum of surface-subsurface hydrologic interactions over a wide range of spatial and temporal scales rather than discrete processes. © 2012. American Geophysical Union. All Rights Reserved. Source

Hooton L.A.,University of Western Ontario | Hooton L.A.,Normandeau Associates Inc. | Dzal Y.A.,University of Western Ontario | Dzal Y.A.,University of British Columbia | And 3 more authors.
Canadian Journal of Zoology | Year: 2016

Sediments of the upper Hudson River, New York, USA, contain polychlorinated biphenyls (PCBs). Consequently, elevated levels of PCBs have been found in the tissues of bats and their insect prey along this region. However, it is not clear whether bat activity and foraging behaviour have been affected. To assess possible effects of PCBs on bat activity and foraging behaviour, we measured the activity of little brown bats (Myotis lucifugus (LeConte, 1831)) and hoary bats (Lasiurus cinereus (Palisot de Beauvois, 1796)) along the upper Hudson River, as well as abundance of insect prey at the same locations. We also measured foraging duration and distances travelled by radio-tagged M. lucifugus.We found that bat activity and insect abundance did not differ with PCB concentration. We did, however, find that foraging behaviour along the Hudson River differed from a control site. Specifically, M. lucifugus foraging along PCBcontaminated areas of the Hudson River travelled shorter distances from their roosts and spent less time foraging than bats at an uncontaminated site. Our results show that while bats roost and forage in areas historically exposed to PCBs, this exposure has not adversely affected bat activity, foraging behaviour, or abundance of insect prey. © 2016, All rights reserved. Source

Trested D.G.,Normandeau Associates Inc. | Chan M.D.,Parsons Brinckerhoff | Bridges W.C.,Clemson University | Jeffery Isely J.,U.S. Geological Survey | Jeffery Isely J.,National Oceanic and Atmospheric Administration
Transactions of the American Fisheries Society | Year: 2011

Long-term restoration efforts for lake sturgeon Acipenser fulvescens populations will benefit from better understanding of this species' movements and habitat use in riverine systems. Radio transmitters were implanted in both juvenile and adult lake sturgeon in the Grasse River, New York, and individuals were relocated over a 2-year period. Adult lake sturgeon demonstrated greater minimum daily distance moved, absolute distance moved, and mean home range size than juvenile lake sturgeon during the spring. During the course of the study, both adult and juvenile lake sturgeon exhibited movements upstream and downstream through a breached low-head weir, and individuals did not necessarily remain resident on an annual basis in the Grasse River. Mesohabitat and substrate use patterns were determined based on comparisons of frequency distributions for relocated lake sturgeon and quantified mesohabitat and substrate over a 15-km river reach. Lake sturgeon used pool mesohabitat and limited their use of runmesohabitat under both low- and mid-flow conditions. During most of the year, adult and juvenile lake sturgeon were detected over silt substrate. This study illustrates behavioral differences and similarities between the movements and habitat use of adult and juvenile lake sturgeon in a riverine system. © American Fisheries Society 2011. Source

Gurshin C.W.D.,Normandeau Associates Inc. | Howell W.H.,University of New Hampshire | Jech J.M.,National Oceanic and Atmospheric Administration
Fisheries Research | Year: 2013

Repeated acoustic and trawl surveys were performed in the Gulf of Maine cod spawning protection area (GOMCSPA) to: (a) describe the spatial and temporal distribution of spring-spawning Atlantic cod (Gadus orhua); (b) estimate their abundance and biomass; and (c) evaluate precision of the survey methods. A fishing vessel equipped with 38- and 120-kHz split-beam echo sounders surveyed once monthly from dusk to dawn along ten parallel transects that covered a 80.8km2 area during April-July 2011. During each survey, two bottom trawl vessels (one with a small mesh net and one with a large mesh net) each made ten tows in parallel behind the acoustic survey vessel. Cod abundance and biomass was derived from acoustic backscatter by a combination of methods: (1) species apportionment based on trawl catch vs. echo classification; (2) in situ vs. predicted target strength; (3) size of elementary distance sampling unit (EDSU) and statistical approach; and (4) with and without dead zone correction. The mean cod density based on echo classification and a 100-m EDSU resulted in a substantially lower coefficient of variation when the variance was estimated by geostatistics compared to any other method used. Based on echo classification, semivariogram modeling revealed that 67-77% of the variance in cod biomass density was explained by a spatial structural component at a range (correlation length) of 2.0-2.4km. Density maps, produced by ordinary kriging, showed cod were relatively widespread in the survey area in May, but congregated at higher densities in areas adjacent to two elevated bathymetric features. Most cod converged to a single location in June, and were at a higher concentration compared to the highest densities observed in May. This congregation decreased in size and density in July. The survey estimates of cod biomass were 184-494 mt in May, 138-617 mt in June, and 39-135 mt in July. Based on echo classification, the biomass for the GOMCSPA, extrapolated from these survey estimates, were 260-466 mt in May, 196-513 mt in June, and 91-198 mt in July. These results provide some evidence that adult Atlantic cod in spawning condition congregated within the GOMCSPA during the seasonal fishing closure, and that the biomass being protected by the closure may have represented 4-5% of the GOM cod spawning stock biomass at the time of the study. © 2012 Elsevier B.V. Source

Discover hidden collaborations