Time filter

Source Type

Whitehorse, Canada

Taylor J.L.,Environmental Dynamics Inc | Arndt S.K.A.,British Columbia Ministry of forests
Transactions of the American Fisheries Society | Year: 2013

This study examined changes in the abundance of juvenile (age-0 and age-1) and adult Burbot Lota lota in Columbia Lake, British Columbia, for the 1991-1999 cohorts. The objectives were to quantify the degree of variation in cohort abundance at different life stages and investigate the timing of recruitment limitation. Adult spawner abundance and age composition were monitored at a tributary spawning site from 1996 to 2001. Juvenile cohort abundance was estimated from 1997 to 1999, providing age-0 abundance indices for the 1997-1999 cohorts and age-1 indices for the 1996-1998 cohorts. The number of tributary spawners declined from about 1,500 in 1996 and 1997 to 86 in 1999 and then rebounded to 995 by 2001. Adult length frequency and age composition showed that this fluctuation reflected periodic influxes of strong cohorts that dominated the spawning population. The strongest new cohort (1999) observed at the tributary in 2001 came from the smallest number of tributary spawners. Substantial differences in the juvenile abundance of cohorts spawned from similar numbers of adults (1996, 1997) suggested a density-independent effect at the egg or larval stage. The 1999 cohort, however, was more abundant than several other cohorts at the adult stage but not at age 0, suggesting a second limiting period after the first growing season. Possible explanations for the exceptional survival of the 1999 cohort include a temporary expansion of interstitial habitat caused by unusually high water levels and low abundance of older Burbot. As large fluctuations in cohort abundance appear to be characteristic of some Burbot populations, inclusion of age composition is recommended for population assessments. Received September 4, 2012; accepted January 30, 2013. © 2013 Copyright Taylor and Francis Group, LLC. Source

Jantunen J.,6 Gillis Place | Macleod A.C.,Environmental Dynamics Inc | Leafloor J.O.,Natural Resources Canada | Scribner K.T.,Michigan State University
Arctic | Year: 2015

Outside of northern Quebec, there is little evidence to confirm reports of nesting by Canada Geese in Arctic habitats of North America, but they nest regularly in the Arctic tundra of West Greenland, from about 62˚ N to as far north as 76.96˚ N, 71.11˚ W. In 2013, we documented successful nesting by a pair of Canada Geese on northern Baffin Island (71.36˚ N, 79.59˚ W), approximately 1200 km north of the nearest known site of regular nesting by this species in northern Quebec. Photographs, egg measurements, and mitochondrial DNA evidence confirmed that these were Canada Geese. Egg laying began around 17 June, the nest of five eggs hatched on 18 July, and we determined that fledging should have occurred around 20 September. Daily mean temperatures on northern Baffin Island fell below freezing after 5 September 2013, and we suspect that the probability of recruitment for this brood was very low. Climate warming in the Arctic is likely to favor northward range expansion by Canada Geese. © The Arctic Institute of North America. Source

Wagner G.N.,Environmental Dynamics Inc | Cooke S.J.,Carleton University | Brown R.S.,Pacific Northwest National Laboratory | Deters K.A.,Pacific Northwest National Laboratory
Reviews in Fish Biology and Fisheries | Year: 2011

Intracoelomic implantation of transmitters into fish requires making a surgical incision, incision closure, and other surgery related techniques; however, the tools and techniques used in the surgical process vary widely. We review the available literature and focus on tools and techniques used for conducting surgery on juvenile salmonids because of the large amount of research that is conducted on them. The use of sterilized surgical instruments properly selected for a given size of fish will minimize tissue damage and infection rates, and speed the wound healing of fish implanted with transmitters. For the implantation of transmitters into small fish, the optimal surgical methods include making an incision on the ventral midline along the linea alba (for studies under 1 month), protecting the viscera (by lifting the skin with forceps while creating the incision), and using absorbable monofilament suture with a small-swaged-on swaged-on tapered or reverse-cutting needle. Standardizing the implantation techniques to be used in a study involving particular species and age classes of fish will improve survival and transmitter retention while allowing for comparisons to be made among studies and across multiple years. This review should be useful for researchers working on juvenile salmonids and other sizes and species of fish. © 2010 Springer Science+Business Media B.V. Source

Antill T.M.,Environmental Dynamics Inc | Naeth M.A.,University of Alberta | Bork E.W.,University of Alberta | Westhaver A.L.,Jasper National Park
Natural Areas Journal | Year: 2012

Invasive plants threaten Canada's National Parks, which have a mandate for conservation of native vegetation. In Jasper National Park, Russian thistle (Salsola tragus L.), an introduced annual forb, has invaded Montane grasslands that constitute critical winter range for bighorn sheep (Ovis canadensis Shaw) and other ungulates. A two year study assessed five strategies for controlling Russian thistle: (1) removal of ungulate grazing; (2) spraying with metsulfuron-methyl; (3) manual pulling of Russian thistle plants; (4) broadcast seeding of native plant species; and (5) integrated weed management combining grazing exclusion, herbicide, and seeding. All treatments that included herbicide reduced Russian thistle, but also removed native forbs. Manual removal of thistle plants reduced the cover and density of the weed, but not final biomass, and may be impractical to implement on large areas. Grazing exclusion resulted in a large decline in Russian thistle density and biomass after two years and coincided with recovery of other forbs, suggesting this weed species is responding to competition and could, therefore, be reduced through management of ungulate grazing pressure. Nomenclature: bighorn sheep, Metsulfuron-methyl, Ovis canadensis Shaw, Russian thistle, Salsola tragus L. Source

Franke A.,University of Alberta | Setterington M.,Environment Canada | Setterington M.,Environmental Dynamics Inc | Court G.,920 108 Street | Birkholz D.,ALS Laboratory Group
Arctic | Year: 2010

The historical decline of the peregrine falcon (Falco peregrinus) in North America was attributed mainly to reproductive failure associated with persistent organochlorine pollutants, in particular DD T (dichloro-diphenyl- trichloroethane). It is generally assumed that declining trends in pesticide loads will be accompanied by a corresponding increase in reproduction. In this study, we concurrently measured occupancy, reproductive performance, and pesticide loads of breeding-aged adults on territory near Rankin Inlet, Nunavut, from 1982 to 2009. Our findings indicate that reproductive success of peregrine falcons in our study population declined despite concomitant reductions in pesticide loads, and that on average, approximately three fewer territories were occupied annually from 2002 to 2009 than were occupied from 1982 to 1989. In addition, the average number of young to reach banding age annually from 2002 to 2009 was approximately half the number banded annually from 1982 to 1989. These results indicate that in recent years fewer pairs have attempted to breed; in addition, those that did breed successfully raised fewer young to banding age. In general, the pesticides examined in this study cannot mechanistically explain either the reduction in occupancy or the decline in reproductive performance. We suggest that the proximate effects of local weather patterns-ultimately associated, either directly or indirectly, with overall climate change-have the greatest potential to explain the altered demographic features of the Rankin Inlet population. © The Arctic Institute of North. Source

Discover hidden collaborations