Time filter

Source Type

King City, Canada

Reurink F.,Wageningen University | Reurink F.,Simon Fraser University | Hentze N.,LGL Ltd | Rourke J.,Hemmera Envirochem Inc | And 2 more authors.
Behavioral Ecology

Many studies have investigated how foraging behavior such as prey choice varies with factors such as prey size or density. Models of such relationships can be applied "in reverse" to translate easily observed foraging behaviors into assays of habitat attributes that cannot (easily) be measured directly. One such model analyzes the speed of a forager flying between patches, where it captures prey. Faster flight shortens the travel time and hence elevates the intake rate, but is increasingly expensive. The model shows that the net intake rate is maximized at the point at which the energetic cost of flight is equivalent to the net rate of intake. Easy-to-measure flight speeds can thus be translated into hard-to-measure foraging intake rates using established flight power relationships. We studied nonbreeding Pacific dunlins (Calidris alpina pacifica) at 4 intertidal sites on the Fraser River estuary, British Columbia, Canada. These sites differed sufficiently that we expected food availability and hence the attainable foraging rate to differ. We measured interpatch flight speeds of dunlins foraging along the tideline within each site. The measured ground speed, calculated airspeed, and the statistically derived zero-wind effect airspeed all differed significantly between sites, matching in rank order our expectation of habitat quality based on their physical differences. Intake rate estimates ranged from 4.10 W (best mudflat) to 3.48 W (poorest). We think it unlikely that we would have been able to find such small differences using direct measures of foraging intake. © 2015 The Author. Source

Carroll E.L.,University of Auckland | Patenaude N.J.,University of Auckland | Patenaude N.J.,LGL Ltd | Childerhouse S.J.,Australian Antarctic Division | And 4 more authors.
Marine Biology

The abundance of New Zealand subantarctic southern right whales (Eubalaena australis) was estimated for the first time using mark-recapture methods based on photo-identification and microsatellite genotyping (13 loci). Individual identification photographs of 383 whales and microsatellite genotypes of 235 whales were collected during annual austral winter field surveys from 1995 to 1998. Given the 4-year survey period and lack of geographic and demographic closure, we estimated super-population abundance using the POPAN Jolly-Seber model implemented in the software programme MARK. Models with constant survivorship but time-varying capture probability and probability of entry into the population were the most suitable due to the survey design. This provided estimates of abundance in 1998 of 908 non-calf whales (95% C. L. = 755, 1,123) for the photo-identification and 910 non-calf whales (95% C. L. = 641, 1,354) for the microsatellite genotype data sets. The current estimate of 900 whales may represent less than 5% of the pre-whaling abundance in New Zealand waters. © 2011 Springer-Verlag. Source

Donaldson M.R.,University of British Columbia | Raby G.D.,Carleton University | Nguyen V.N.,Carleton University | Hinch S.G.,University of British Columbia | And 11 more authors.
Canadian Journal of Fisheries and Aquatic Sciences

We evaluate the utility of an inexpensive, portable recovery bag designed to facilitate recovery of fish from capture stress by combining physiological assays, biotelemetry, and social science surveys. Adult migrating Pacific salmon (Oncorhynchus spp.) were used as a model, since some of their populations are threatened. While catch-and-release is common, there is a need to ensure that it is sustainable. A social science survey revealed that anglers generally have positive attitudes towards recovery bag use, particularly if research identifies that such techniques could be effective. Physiological assays on pink salmon (Oncorhynchus gorbuscha) revealed benefits of both highand low-velocity recovery, but high velocity was most effective with reduced plasma cortisol concentrations and similar plasma sodium and chloride concentrations as those found in controls at all recovery durations. A biotelemetry study on sockeye salmon (Oncorhynchus nerka) captured by anglers and stressed by air exposure then placed in recovery bags had 20% higher, but not significantly different, survival than no-recovery salmon. The integration of natural science and social science provides an important step forward in developing methods for promoting recovery of fish from capture. Source

Koski W.R.,LGL Ltd | Abgrall P.,LGL Ltd | Yazvenko S.B.,Second Street
Journal of Cetacean Research and Management

A literature review, internet searches and communications with personnel working with unmanned aerial systems (UAS) were used to identify the capabilities of UAS throughout the world. We assessed their ability to replace manned aerial surveys for marine mammals,sea turtles and seabirds and to monitor, in real time, sea ice and other physical features that might influence marine mammal distribution. The vast majority of the systems identified were either too expensive or their capabilities did not meet minimum standards necessary to perform the tasks required of them in real time. Eight systems were identified that might be able to perform some of the desired tasks. Several other systems had similarcapabilities but had not been tested or would require upgrades. Installation of high-definition (HD) video and better stabilisation systems would improve UAS performance. It is recommended that development of HD video with real-time data transmission and improved stabilisation systems for UAS be pursued and that side-by-side comparisons of a few of the best systems be conducted. Source

Koski W.R.,LGL Ltd | Zeh J.,University of Washington | Mocklin J.,National Oceanic and Atmospheric Administration | Davis A.R.,LGL Ltd | And 3 more authors.
Journal of Cetacean Research and Management

Ice-based surveys near Point Barrow, Alaska, have been used to obtain most estimates of abundance for the Bering-Chukchi-Beaufort (B-C-B) stock of bowhead whales, but global warming has raised concerns that ice-based surveys may not be practical in the future. Aerial photographic surveys provide an alternative method for obtaining abundance estimates and may replace ice-based surveys. Aerial photographic surveys were conducted near Point Barrow during the spring migrations of bowhead whales in 2003 and 2004 and, in 2005, in the northern Bering Sea in spring and near Barrow in fall. The 2003 survey was the most complete photographic survey of the population conducted to date. These surveys provided photo-identification data for use in capture-recapture analyses. A screening procedure was used to define which whales captured in 2003, 2004 and/or 2005 were marked and could be reidentified if photographed on another occasion. An estimate of the number of marked whales was obtained using a closed population model for capture-recapture data. Several models were investigated, including models that accounted for heterogeneity in capture probabilities, but a simple model with no covariates produced the most precise estimate. To account for unmarked whales, the estimate of marked whales was divided by an estimate of the proportion of the bowhead population that was marked based on the 1989-2004 spring photographic surveys near Point Barrow. Abundance of the B-C-B bowhead population in 2004 (excluding calves) was estimated to be 12,631 with CV 0.2442,95% bootstrap percentile confidence interval (7,900; 19,700) and 5% lower limit 8,400. These results were compared with results that used approximate variance expressions for the estimates of the number of marked whales, the proportion of the population that was marked and population abundance instead of using the bootstrap. The estimates of abundance in 2004 computed for comparison included one based on a modified Petersen estimate of the number of marked whales that omitted the 2005 data as well as the estimate of 12,631 described above. The comparison estimates also included estimates of abundance in 1985 computed from 1984-87 photographic survey data using the same methods. AU the abundance estimates computed from photographic data were consistent with expectations based on independent abundance and trend estimates from the ice-based surveys conducted from 1978 to 2001. Source

Discover hidden collaborations