Browsing by Author "Schroeder, Leslie"

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    Data and R code to support: Estimating densities of zebra mussels (Dreissena polymorpha) in early invasions using distance sampling
    (2019-01-18) Ferguson, Jake M; Fieberg, John R; McCartney, Michael A.; Blinick, Naomi S.; Schroeder, Leslie; jakeferg@umn.edu; Ferguson, Jake M; Minnesota Aquatic Invasive Species Research Center
    These files are the data and code needed to reproduce the analysis of the manuscript "Estimating densities of zebra mussels (Dreissena polymorpha) in early invasions using distance sampling". The data include spatial coordinates of transects used to survey for zebra mussels in Lake Sylvia and Lake Burgan in the summer of 2017, the counts of zebra mussels on each transect, and environmental covariates collected along transects and at each detection. We also provide the R code needed to process and analyze these data following the distance survey approach described in the manuscript. We provide code for a straightforward distance survey, which doesn't include any spatial covariate information, as well as a more computationally intensive analysis that does include spatial covariates.
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    Die another day; Growth model reveals high natural survival rates in loggerhead sea turtles
    (2017-07) Schroeder, Leslie
    Accurate survival estimates are essential to sea turtle conservation but difficult to estimate due to anthropogenic mortality and confounding factors such as tag loss and emigration. The Lester Growth Model allows for the estimation of sex-specific adult natural survival rates (the rate that a population would experience independent of human influence) from length-at-age and maturity data. I applied this model to individual loggerheads of the Northwest Atlantic subpopulation. Both male and female annual natural survival rates were estimated to be 96-97%; ~0.14 higher than published total survival values. This result was corroborated by a population model designed to estimate a range of possible adult survival rates. These natural survival rates, in conjunction with published rates, allow for the estimation of anthropogenic mortality and assessment of the impact of confounding factors on mark-recapture studies. It is likely that this technique can be leveraged for other loggerhead populations and sea turtle species.