Roberts Jason J.

No Thumbnail Available
Last Name
First Name
Jason J.

Search Results

Now showing 1 - 3 of 3
  • Article
    Striking the right balance in right whale conservation
    (NRC Research Press, 2009-08-14) Schick, Robert S. ; Halpin, Patrick N. ; Read, Andrew J. ; Slay, Christopher K. ; Kraus, Scott D. ; Mate, Bruce R. ; Baumgartner, Mark F. ; Roberts, Jason J. ; Best, Benjamin D. ; Good, Caroline P. ; Loarie, Scott R. ; Clark, James S.
    Despite many years of study and protection, the North Atlantic right whale (Eubalaena glacialis) remains on the brink of extinction. There is a crucial gap in our understanding of their habitat use in the migratory corridor along the eastern seaboard of the United States. Here, we characterize habitat suitability in migrating right whales in relation to depth, distance to shore, and the recently enacted ship speed regulations near major ports. We find that the range of suitable habitat exceeds previous estimates and that, as compared with the enacted 20 nautical mile buffer, the originally proposed 30 nautical mile buffer would protect more habitat for this critically endangered species.
  • Article
    Counting whales in a challenging, changing environment
    (Nature Publishing Group, 2014-03-13) Williams, R. ; Kelly, N. ; Boebel, Olaf ; Friedlaender, Ari S. ; Herr, H. ; Kock, K.-H. ; Lehnert, L. S. ; Maksym, Ted ; Roberts, Jason J. ; Scheidat, M. ; Siebert, U. ; Brierley, A. S.
    Estimating abundance of Antarctic minke whales is central to the International Whaling Commission's conservation and management work and understanding impacts of climate change on polar marine ecosystems. Detecting abundance trends is problematic, in part because minke whales are frequently sighted within Antarctic sea ice where navigational safety concerns prevent ships from surveying. Using icebreaker-supported helicopters, we conducted aerial surveys across a gradient of ice conditions to estimate minke whale density in the Weddell Sea. The surveys revealed substantial numbers of whales inside the sea ice. The Antarctic summer sea ice is undergoing rapid regional change in annual extent, distribution, and length of ice-covered season. These trends, along with substantial interannual variability in ice conditions, affect the proportion of whales available to be counted by traditional shipboard surveys. The strong association between whales and the dynamic, changing sea ice requires reexamination of the power to detect trends in whale abundance or predict ecosystem responses to climate change.
  • Article
    Extrapolating cetacean densities to quantitatively assess human impacts on populations in the high seas
    (John Wiley & Sons, 2017-04-28) Mannocci, Laura ; Roberts, Jason J. ; Miller, David L. ; Halpin, Patrick N.
    As human activities expand beyond national jurisdictions to the high seas, there is an increasing need to consider anthropogenic impacts to species inhabiting these waters. The current scarcity of scientific observations of cetaceans in the high seas impedes the assessment of population-level impacts of these activities. We developed plausible density estimates to facilitate a quantitative assessment of anthropogenic impacts on cetacean populations in these waters. Our study region extended from a well-surveyed region within the U.S. Exclusive Economic Zone into a large region of the western North Atlantic sparsely surveyed for cetaceans. We modeled densities of 15 cetacean taxa with available line transect survey data and habitat covariates and extrapolated predictions to sparsely surveyed regions. We formulated models to reduce the extent of extrapolation beyond covariate ranges, and constrained them to model simple and generalizable relationships. To evaluate confidence in the predictions, we mapped where predictions were made outside sampled covariate ranges, examined alternate models, and compared predicted densities with maps of sightings from sources that could not be integrated into our models. Confidence levels in model results depended on the taxon and geographic area and highlighted the need for additional surveying in environmentally distinct areas. With application of necessary caution, our density estimates can inform management needs in the high seas, such as the quantification of potential cetacean interactions with military training exercises, shipping, fisheries, and deep-sea mining and be used to delineate areas of special biological significance in international waters. Our approach is generally applicable to other marine taxa and geographic regions for which management will be implemented but data are sparse.