LGL Ltd environmental research associates
LGL Ltd environmental research associates
Gregory P.T.,University of Kent |
Tuttle K.N.,University of Victoria |
Tuttle K.N.,LGL Ltd Environmental Research Associates
Herpetologica | Year: 2016
An animal's decision to stay in a protective refuge or venture from it will depend on the exigencies of other necessary functions (e.g., feeding, breeding, thermoregulation), which often will interact themselves. In this study, we determined broad patterns of use of cover objects in five species of diurnal natricine snakes at two locations in Canada and one location in the UK. In particular, we focused on the influence of body size (larger snakes should incur less risk away from cover) and reproductive state (gravid snakes thermoregulate precisely and therefore should often bask) on the probability that a snake will be found in the open. As we predicted, body size influenced the likelihood of being in the open, both within and between species (one small species was almost always found under cover), even when we took time of day, season, or both into account. Such relationships are unlikely to be solely caused by the thermoregulatory role of cover, and we argue that small snakes sometimes sacrifice basking opportunities to take advantage of the protective qualities of cover. However, small snakes might use cover to avoid dehydration as well as predators. As we also predicted, gravid females were more likely to be in the open at a given body size than other snakes, but only in the three largest viviparous species the smallest species and one oviparous species showed no such effect. In general, body size and reproductive state both determine cover-use behavior. Studies of use of other kinds of cover or refuges by snakes (e.g., vegetation, underground burrows), and of time spent under cover vs. in the open, would help test the generality of our conclusions. © 2016 by The Herpetologists' League, Inc.
Schweder T.,University of Oslo |
Sadykova D.,University of Oslo |
Rugh D.,National Oceanic and Atmospheric Administration |
Koski W.,LGL Ltd environmental research associates
Journal of Agricultural, Biological, and Environmental Statistics | Year: 2010
Abundance, mortality, and population growth of bowhead whales (Balaenamysticetus) are estimated from captures of 4,894 putatively different individuals obtained from 10 years of systematic photographic surveys conducted during the spring migration when most of the Bering-Chukchi-Beaufort population of bowheads migrates past Point Barrow, Alaska. A stringent matching protocol designed to prevent false positive matches of the naturally, but variably marked individuals, led to 42 resightings between years. The flip side of this stringency is a presence of false negatives, i. e., some true recaptures are not recognized as such. The problem of false negatives is addressed by modeling the capture process and the matching process. The captures of an individual are assumed to follow a Poisson process with intensity depending stochastically on the individual whale and on the year. The probability of successfully matching a capture to a previous capture is estimated by logistic regression on the degree of marking and image quality. Individuals are recruited by the Pella-Tomlinson population model, and their mortality rate is assumed to be constant. The point estimate of yearly growth rate is 3. 2%, and bowhead abundance in 2001 is estimated to be 8,250, similar to previous estimates. © 2009 International Biometric Society.
Edgell T.C.,LGL Ltd Environmental Research Associates |
Edgell T.C.,Stantec Inc. |
Demarchi M.W.,LGL Ltd Environmental Research Associates
Marine Ecology Progress Series | Year: 2012
Populations of California sea lions Zalophus californianus and Steller sea lions Eumetopias jubatus in much of the eastern North Pacific Ocean have experienced significant growth since being protected in the early 1970s (by the US Marine Mammal Protection Act and Canada's Fisheries Act) from commercial harvests and fisheries-related culls. However, there remains substantial and unexplained variance in the annual number of sea lions using a major winter haulout at the entrance to the Salish Sea. We used linear regression on principal components to show maximum annual sea lion counts, adjusted for population growth, varied as a function of herring biomass and not local sea surface temperatures or precipitation. Results suggest that Race Rocks, British Columbia, Canada, is used as a stopover for an increasing number of sea lions approaching southern Vancouver Island to feed during the nonbreeding season. Reports of resource-driven movements of sea lions are not new, but this is the first study to use a multidecade data set to show resource-driven movements can underlie long-term patterns of population growth. Finally, we found an unexplained change in the seasonal use of Race Rocks affecting both species. Arrival at Race Rocks has occurred in late summer since 1965, but up to 1979 departure had occurred the following spring; since as late as 1997, departure has occurred mid winter. This study highlights the complexities of enacting conservation plans for species with latitudinal distributions and undergoing long-term population change. © Inter-Research 2012.
Pinno B.D.,Natural Resources Canada |
Hawkes V.C.,LGL Ltd environmental research associates
Forests | Year: 2015
Forest development after land reclamation in the oil sands mining region of northern Alberta, Canada was assessed using long-term monitoring plots from both reclaimed and natural forests. The metrics of ecosystem development analyzed included measures of plant community structure and composition and soil nutrient availability. Early seral reclamation plots were grouped by site type (dry and moist-rich) and age categories, and these were compared with mature natural forests. There were few significant differences in ecosystem metrics between reclamation site types, but natural stands showed numerous significant differences between site types. Over time, there were significant changes in most plant community metrics such as species richness and cover of plant community groups (e.g., forbs, shrubs, and non-native species), but these were still substantially different from mature forests 20 years after reclamation. Available soil nitrogen did not change over time or by reclamation site type but available soil phosphorus did, suggesting that phosphorus may be a more suitable indicator of ecosystem development. The significant temporal changes in these reclaimed ecosystems indicate that studies of ecosystem establishment and development on reclaimed areas should be conducted over the long-term, emphasizing the utility of monitoring using long-term plot networks. © 2015 by the authors.
Evans T.G.,Canadian Department of Fisheries and Oceans |
Hammill E.,Canadian Department of Fisheries and Oceans |
Kaukinen K.,Canadian Department of Fisheries and Oceans |
Schulze A.D.,Canadian Department of Fisheries and Oceans |
And 4 more authors.
Molecular Ecology | Year: 2011
Environmental shifts accompanying salmon spawning migrations from ocean feeding grounds to natal freshwater streams can be severe, with the underlying stress often cited as a cause of increased mortality. Here, a salmonid microarray was used to characterize changes in gene expression occurring between ocean and river habitats in gill and liver tissues of wild migrating sockeye salmon (Oncorhynchus nerka Walbaum) returning to spawn in the Fraser River, British Columbia, Canada. Expression profiles indicate that the transcriptome of migrating salmon is strongly affected by shifting abiotic and biotic conditions encountered along migration routes. Conspicuous shifts in gene expression associated with changing salinity, temperature, pathogen exposure and dissolved oxygen indicate that these environmental variables most strongly impact physiology during spawning migrations. Notably, transcriptional changes related to osmoregulation were largely preparatory and occurred well before salmon encountered freshwater. In the river environment, differential expression of genes linked with elevated temperatures indicated that thermal regimes within the Fraser River are approaching tolerance limits for adult salmon. To empirically correlate gene expression with survival, biopsy sampling of gill tissue and transcriptomic profiling were combined with telemetry. Many genes correlated with environmental variables were differentially expressed between premature mortalities and successful migrants. Parametric survival analyses demonstrated a broad-scale transcriptional regulator, cofactor required for Sp1 transcriptional activation (CRSP), to be significantly predictive of survival. As the environmental characteristics of salmon habitats continue to change, establishing how current environmental conditions influence salmon physiology under natural conditions is critical to conserving this ecologically and economically important fish species. © 2011 Blackwell Publishing Ltd.
Goudie R.I.,LGL Ltd Environmental Research Associates |
Scheidegger C.,Swiss Federal Institute of forest |
Hanel C.,Environment Canada |
Munier A.,Royal Roads University |
Conway E.,Harbour Group
Endangered Species Research | Year: 2011
A preliminary population model was developed for the boreal felt lichen Erioderma pedicellatum (Hue) P. M. Jørg. in Newfoundland using life stage data collected in eastern and south-central Newfoundland, Canada. This Critically Endangered epiphytic lichen displayed a life history strategy with high adult survival and low recruitment. Deterministic models in 6 mo to 1 yr intervals were generated, yielding similar results to the overall mean values for the 4 yr of study in eastern Newfoundland. The populations of E. pedicellatum in Newfoundland are predicted by our models to be unsustainable because of adult mortality, and we attribute this problem to a decline in the forests of balsam fir Abies balsamea (Mill) that predominantly support this lichen. In eastern Newfoundland, thalli are located almost entirely on mature to over-mature balsam fir, and there is little regeneration because of heavy browsing by the introduced moose Alces alces population. The current and projected predictors indicate that habitat effects may be important in predicting future population size. An assessment of the stable stage distribution indicated that the current population has more juveniles and fewer apothecia-bearing thalli than projected, meaning the current population likely generated from a different set of survival and recruitment rates. The projected annual population growth rates calculated for 4 yr indicated that populations are declining (λ < 1.0, mean decline ± SD = -0.175 ± 0.079). The elasticity values support the fact that the population growth rates are most sensitive to changes in the survival of necrotic (apothecia-bearing) cohorts. We suggest that conservation is best focused on the inventory and protection of old-growth forests important to this species, the reduction of the introduced moose population and the use of herbivore exclosures in specific core population areas. © Inter-Research 2011.
Broker K.,Royal Dutch Shell |
Gailey G.,Texas A&M University |
Muir J.,LGL Ltd environmental research associates |
Racca R.,JASCO Applied science
Endangered Species Research | Year: 2015
A 4D seismic survey was conducted in 2010 near the feeding grounds of gray whales off Sakhalin Island, Russia. To minimize disruptions to the whales' feeding activity and enhance understanding of the potential impacts of seismic surveys on gray whales Eschrichtius robustus, an extensive monitoring and mitigation plan (MMP) was developed. Typically, mitigation plans involve observers on seismic vessels to monitor for the presence of marine mammals in an exclusion zone so as to prevent physical injury to the animals. Due to the protected status of western gray whales, an additional protection zone based on a behavioural disturbance threshold of exposure of 156 dB re μPa2-s per pulse was applied for whales within their feeding habitat defined by the estimated 95% abundance contour. Real-time radio-transmitting acoustic recorders were deployed along this contour to verify modelled acoustic footprints within the feeding grounds. Shore- and vessel-based observation teams monitored for the presence and activity of whales. A real-time GIS workflow tracking procedure was developed that integrated acoustic and whale positioning data to determine if sound levels at a whales' position within the feeding area exceeded the behavioural threshold, in which case a shut-down of the seismic source was implemented. Additionally, behaviour and distribution surveys were conducted before, during and after the seismic survey to evaluate the effectiveness of the MMP. No large changes in whale movement, respiration, or distribution patterns were observed during the seismic survey. This could be interpreted to mean that the MMP was effective in reducing the sound exposure and behavioural responses of gray whales to seismic sounds. © The authors 2015.
Nelson T.C.,Fraser River Sturgeon Conservation Society |
Gazey W.J.,Wj Gazey Research |
English K.K.,LGL Ltd Environmental Research Associates |
Rosenau M.L.,British Columbia Institute of Technology
Fisheries | Year: 2013
Sturgeon (Acipenseridae) stocks worldwide are generally in decline, with many populations close to extirpation. One prominent species, the White Sturgeon (Acipenser transmontanus), with spawning populations distributed throughout three large, western North American watersheds (the Sacramento, Columbia, and Fraser rivers), has experienced population declines in the past decade. In 2003, the Committee on the Status of Endangered Wildlife in Canada designated all six populations of White Sturgeon in Canada "endangered." To assist sturgeon recovery initiatives in the lower Fraser River (British Columbia), a stewardship-based monitoring and assessment program was developed by the Fraser River Sturgeon Conservation Society. A descriptive population model was developed to provide reliable annual population estimates by size/age group and location, based on tag release and recapture data collected by trained volunteers. As of January 2011, the population estimate (from 40- to 279-cm fork length) was 44,713 (95% confidence level 42,634-46,792). Group size analyses suggest that abundance decreases have been greatest for juvenile sturgeon under 100-cm fork length. Recruitment decline may be the result of several factors, including destruction of important spawning and early life history rearing habitats; fewer successful adult spawners due to in-river fisheries; and/or impacts of reduced food supply and ecological imbalances on both early life and adult stages.
Higdon J.W.,University of Manitoba |
Higdon J.W.,University of Winnipeg |
Hauser D.D.W.,78 Marine Drive |
Hauser D.D.W.,LGL Ltd Environmental Research Associates |
And 2 more authors.
Marine Mammal Science | Year: 2012
Killer whales (Orcinus orca) have a global distribution, but many high-latitude populations are not well studied. We provide a comprehensive review of the history and ecology of killer whales in the Canadian Arctic, for which there has previously been little information. We compiled a database of 450 sightings spanning over 15 decades (1850-2008) to document the historical occurrence, distribution, feeding ecology, and seasonality of killer whales observed throughout the region. Sighting reports per decade increased substantially since 1850 and were most frequent in the eastern Canadian Arctic. The mean reported group size was 8.3 (median = 4, range 1-100), but size varied significantly among regions and observed prey types. Observations of predation events indicate that Canadian Arctic killer whales prey upon other marine mammals. Monodontids were the most frequently observed prey items, followed by bowhead whales (Balaena mysticetus), phocids, and groups of mixed mammal prey. No killer whale sightings occurred during winter, with sightings gradually increasing from early spring to a peak in summer, after which sightings gradually decreased. Our results suggest that killer whales are established, at least seasonally, throughout the Canadian Arctic, and we discuss potential ecological implications of increased presence with declining sea ice extent and duration. © 2011 by the Society for Marine Mammalogy.
Crossman J.A.,BC Hydro |
Martel G.,BC Hydro |
Johnson P.N.,LGL Ltd Environmental Research Associates |
Bray K.,BC Hydro
Journal of Applied Ichthyology | Year: 2011
The feasibility of using Dual-frequency IDentification SONar (DIDSON) for monitoring white sturgeon (Acipenser transmontanus) presence and activity was tested near a known spawning area in the Columbia River, British Columbia, Canada. A fixed-station DIDSON system was deployed near the river bank adjacent to the spawning site in each 3years (2007-2009). Fixed-station data were collected at this site in July and August each year, with an additional fixed-station site established in 2009 approximately 1.6km upstream. A total of 267, 64, and 210 observations of sturgeon were documented based on fixed-station DIDSON sampling in 2007, 2008, and 2009, respectively. Sturgeon detections within the sample area (standardized by time and day) generally increased during late evening/early morning hours but did not appear to be related to flows. The DIDSON provided estimates of white sturgeon total lengths consistent with known length distributions for this population. Most sturgeon were detected at least 10m away from the shoreline. These results demonstrate the feasibility of using fixed-station DIDSON for remotely monitoring white sturgeon in areas of known use. Observational data from this study also provided information on general sturgeon behaviour that is often difficult to assess with more conventional sampling methods. © 2011 Blackwell Verlag, Berlin.