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.
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.
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.
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.