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Mervi Kunnasranta - One of the best experts on this subject based on the ideXlab platform.

  • a Mark Recapture approach for estimating population size of the endangered ringed seal phoca hispida saimensis
    PLOS ONE, 2019
    Co-Authors: Meeri Koivuniemi, Mika Kurkilahti, Marja Niemi, Miina Auttila, Mervi Kunnasranta
    Abstract:

    Reliable population estimates are fundamental to the conservation of endangered species. We evaluate here the use of photo-identification (photo-ID) and Mark-Recapture techniques for estimating the population size of the endangered Saimaa ringed seal (Phoca hispida saimensis). Photo-ID data based on the unique pelage patterns of individuals were collected by means of camera traps and boat-based surveys during the molting season in two of the species’ main breeding areas, over a period of five years in the Pihlajavesi basin and eight years in the Haukivesi basin. An open model approach provided minimum population estimates for these two basins. The results indicated high survival rates and site fidelity among the adult seals. More accurate estimates can be obtained in the future by increasing the surveying effort both spatially and temporally. The method presented here proved effective for evaluating population size objectively, whereas the results of the current snow lair censuses are dependent on varying winter conditions, for instance. We therefore suggest that a photo-ID-based non-invasive Mark-Recapture method should be used for estimating Saimaa ringed seal abundances in order to ensure reliable, transparent population monitoring under changing climatic conditions.

  • A Mark–Recapture approach for estimating population size of the endangered ringed seal (Phoca hispida saimensis)
    2019
    Co-Authors: Meeri Koivuniemi, Mika Kurkilahti, Marja Niemi, Miina Auttila, Mervi Kunnasranta
    Abstract:

    Reliable population estimates are fundamental to the conservation of endangered species. We evaluate here the use of photo-identification (photo-ID) and Mark-Recapture techniques for estimating the population size of the endangered Saimaa ringed seal (Phoca hispida saimensis). Photo-ID data based on the unique pelage patterns of individuals were collected by means of camera traps and boat-based surveys during the molting season in two of the species’ main breeding areas, over a period of five years in the Pihlajavesi basin and eight years in the Haukivesi basin. An open model approach provided minimum population estimates for these two basins. The results indicated high survival rates and site fidelity among the adult seals. More accurate estimates can be obtained in the future by increasing the surveying effort both spatially and temporally. The method presented here proved effective for evaluating population size objectively, whereas the results of the current snow lair censuses are dependent on varying winter conditions, for instance. We therefore suggest that a photo-ID-based non-invasive Mark-Recapture method should be used for estimating Saimaa ringed seal abundances in order to ensure reliable, transparent population monitoring under changing climatic conditions.

John Boulanger - One of the best experts on this subject based on the ideXlab platform.

  • multiple data sources improve dna based Mark Recapture population estimates of grizzly bears
    Ecological Applications, 2008
    Co-Authors: John Boulanger, Katherine C Kendall, Jeffrey B Stetz, David A Roon, Lisette P Waits, David Paetkau
    Abstract:

    A fundamental challenge to estimating population size with Mark-Recapture methods is heterogeneous capture probabilities and subsequent bias of population estimates. Confronting this problem usually requires substantial sampling effort that can be difficult to achieve for some species, such as carnivores. We developed a methodology that uses two data sources to deal with heterogeneity and applied this to DNA Mark-Recapture data from grizzly bears (Ursus arctos). We improved population estimates by incorporating additional DNA "captures" of grizzly bears obtained by collecting hair from unbaited bear rub trees concurrently with baited, grid-based, hair snag sampling. We consider a Lincoln-Petersen estimator with hair snag captures as the initial session and rub tree captures as the Recapture session and develop an estimator in program Mark that treats hair snag and rub tree samples as successive sessions. Using empirical data from a large-scale project in the greater Glacier National Park, Montana, USA, area and simulation modeling we evaluate these methods and compare the results to hair-snag-only estimates. Empirical results indicate that, compared with hair-snag-only data, the joint hair-snag-rub-tree methods produce similar but more precise estimates if capture and Recapture rates are reasonably high for both methods. Simulation results suggest that estimators are potentially affected by correlation of capture probabilities between sample types in the presence of heterogeneity. Overall, closed population Huggins-Pledger estimators showed the highest precision and were most robust to sparse data, heterogeneity, and capture probability correlation among sampling types. Results also indicate that these estimators can be used when a segment of the population has zero capture probability for one of the methods. We propose that this general methodology may be useful for other species in which Mark-Recapture data are available from multiple sources.

  • an empirical test of dna Mark Recapture sampling strategies for grizzly bears
    Ursus, 2006
    Co-Authors: John Boulanger, Stefan Himmer, Michael F Proctor, David Paetkau, Gordon B Stenhouse, Jerome Cranston
    Abstract:

    Abstract Despite the widespread use of DNA Mark–Recapture for estimation of grizzly bear (Ursus arctos) population size, there have been no designed experiments of DNA sampling strategies. We designed a large-scale study (8,820 km2) in the foothills of Alberta, Canada, to test sampling strategies associated with the hair snag DNA method. The main sampling method for this project used a traditional design in which bait sites were moved within 180 7 x 7 km grid cells for 4 2-week sampling sessions in the spring of 2004. However, we also tested other strategies concurrently with the traditional design. We sampled fixed sites within each cell to test the utility of moving sites compared to the less-expensive method of not moving sites. We also placed a second, lower strand of barbed wire on bait sites to see if this could identify cubs, which are not typically sampled by the usual knee-height strand of barbed wire. We compared summary statistics, capture probability variation, population estimates, and the pr...

  • sources of heterogeneity bias when dna Mark Recapture sampling methods are applied to grizzly bear ursus arctos populations
    Journal of Mammalogy, 2004
    Co-Authors: John Boulanger, Gordon B Stenhouse, Robin Munro
    Abstract:

    One of the challenges in estimating grizzly bear (Ursus arctos) population size using DNA methods is heterogeneity of capture probabilities. This study developed general tools to explore heterogeneity variation using data from a DNA Mark-Recapture project in which a proportion of the bear population had GPS collars. The Huggins closed population Mark-Recapture model was used to determine if capture probability was influenced by sex or collar status. In addition, trap encounter rates were estimated by comparing the closest distance from traps where hair was snagged of bears that were captured, with bears for which we had radiolocations but were not captured. Results of the Huggins analysis suggested that sex, distance of bear DNA capture from grid edge, and whether a bear was radiocollared potentially affected capture probabilities. The encounter rate analysis estimated that 63% of bears that encountered traps were snagged, and that males encountered more traps than females. The following conclusions arise from this study. First, the distance of DNA capture of bears relative to the grid edge should be modeled as an individual covariate to ensure robust estimates of superpopulation size when closure violation is suspected. Second, sampling should be intensive to minimize heterogeneity and to ensure all bears encounter traps. Finally, estimators that are robust to heterogeneity variation should be used, given the various sources of heterogeneity variation.

  • monitoring of grizzly bear population trends and demography using dna Mark Recapture methods in the owikeno lake area of british columbia
    Canadian Journal of Zoology, 2004
    Co-Authors: John Boulanger, Stefan Himmer, C Swan
    Abstract:

    We used DNA sampling and Mark–Recapture modeling to estimate population trend(s), population size, and the demographic response of a coastal British Columbia grizzly bear population (Ursus arctos L...

  • sampling design and bias in dna based capture Mark Recapture population and density estimates of grizzly bears
    Journal of Wildlife Management, 2004
    Co-Authors: John Boulanger, Bruce N. Mclellan, John G Woods, Michael F Proctor, Curtis Strobeck
    Abstract:

    Abstract Over a 3-year period, we assessed 2 sampling designs for estimating grizzly bear (Ursus arctos) population size using DNA capture–Mark–Recapture methods on a population of bears that included radioMarked individuals. We compared a large-scale design (with 8 × 8-km grid cells and sites moved for 4 sessions) and a small-scale design (5 × 5-km grid cells with sites not moved for 5 sessions) for closure violation, capture-probability variation, and estimate precision. We used joint telemetry/capture–Mark–Recapture (JTMR) analysis and traditional closure tests to analyze the capture–Mark–Recapture data with each design. A simulation study compared the performance of each design for robustness to heterogeneity bias caused by reduced capture probabilities of cubs. Our results suggested that the 5 × 5-km grid cell design was more precise and more robust to potential sample biases, but the risk of closure violation due to smaller overall grid size was greater. No design exhibited complete closure as estim...

Samu Mantyniemi - One of the best experts on this subject based on the ideXlab platform.

Adam Barnett - One of the best experts on this subject based on the ideXlab platform.

  • Integrating acoustic telemetry into Mark-Recapture models to improve the precision of apparent survival and abundance estimates
    Oecologia, 2015
    Co-Authors: Christine L. Dudgeon, Jayson M. Semmens, Kenneth H. Pollock, J. Matias Braccini, Adam Barnett
    Abstract:

    Capture–Mark–Recapture models are useful tools for estimating demographic parameters but often result in low precision when Recapture rates are low. Low Recapture rates are typical in many study systems including fishing-based studies. Incorporating auxiliary data into the models can improve precision and in some cases enable parameter estimation. Here, we present a novel application of acoustic telemetry for the estimation of apparent survival and abundance within capture–Mark–Recapture analysis using open population models. Our case study is based on simultaneously collecting longline fishing and acoustic telemetry data for a large mobile apex predator, the broadnose sevengill shark (Notorhynchus cepedianus), at a coastal site in Tasmania, Australia. Cormack–Jolly–Seber models showed that longline data alone had very low Recapture rates while acoustic telemetry data for the same time period resulted in at least tenfold higher Recapture rates. The apparent survival estimates were similar for the two datasets but the acoustic telemetry data showed much greater precision and enabled apparent survival parameter estimation for one dataset, which was inestimable using fishing data alone. Combined acoustic telemetry and longline data were incorporated into Jolly–Seber models using a Monte Carlo simulation approach. Abundance estimates were comparable to those with longline data only; however, the inclusion of acoustic telemetry data increased precision in the estimates. We conclude that acoustic telemetry is a useful tool for incorporating in capture–Mark–Recapture studies in the marine environment. Future studies should consider the application of acoustic telemetry within this framework when setting up the study design and sampling program.

Daniel D Roby - One of the best experts on this subject based on the ideXlab platform.