[MARMAM] New Paper Available
Dear MARMAMers, My co-authors and I are pleased to announce the publication of the following paper: Jefferson, T. A., M. A. Smultea and E. J. Ward. (2023). Distribution and Abundance of California (Zalophus californianus) and Steller (Eumetopias jubatus) Sea Lions in the Inshore Waters of Washington, 2013-2016. Aquatic Mammals, 49, 366-381. https://doi.org/10.1578/am.49.4.2023.366ABSTRACT: Two species of sea lions occur in the inlandwaters of Washington State, the California sea lion (Zalophus californianus) and Steller sea lion (Eumetopias jubatus). Both species breed elsewhere, but typically moveinto Puget Sound and adjacent waters of the Salish Sea from autumn throughspring months. There is a need forinformation on their current abundance and seasonal use patterns, as bothspecies prey heavily on threatened/endangered stocks of salmon and steelheadtrout (Oncorhynchus spp.), andempirical abundance estimates of these species are lacking for inlandWashington waters. From 2013-2016, we conducted 39,399 km of aerial surveys formarine mammals in this area, sighting 255 groups of sea lions. We used a subset of 7,841 km of effort and165 sea lion sightings made during surveys in good sighting conditions toestimate in-water abundance using line-transect methods. Historical tagging data collected in PacificNorthwest waters were used to evaluate the proportions of time that eachspecies spent on land and conducting dives, and then to develop correctionfactors to derive total abundance for both sea lion species, providing the firstempirical abundance estimates for these waters. We estimated that between 33 and 442 California sea lions were found inPuget Sound/Hood Canal in different seasons, with nearly 3,000 being found in thebroader inland Washington waters in the peak season (spring). Steller sea lions occurred in much smallernumbers, with a peak of 219 animals in Puget Sound/Hood Canal/Strait of Juan deFuca in autumn (and possibly as many as 600-700 in the entire study area). Whilesome estimates suffer from low precision, this study demonstrates thatsubstantial numbers of sea lions use waters of the study area throughout muchof the year. Our results provide animportant step toward better understanding of these two species in the inlandwaters of Washington, as well as their potential effects on protected salmonidprey species. The paper is available upon request or from the Aquatic Mammals website. Tom Jefferson ___ MARMAM mailing list MARMAM@lists.uvic.ca https://lists.uvic.ca/mailman/listinfo/marmam
[MARMAM] New Paper Available
Dear MARMAMers, My co-authors and I are pleased to announce the publication of the following paper: Jefferson, T. A., E. A. Becker and S. L. Huang. (2023). Influences of natural and anthropogenic habitat variables on Indo-Pacific humpback dolphins Sousa chinensis in Hong Kong. Endangered Species Research, 51, 143-160. https://doi.org/10.3354/esr01249ABSTRACT: Indo-Pacific humpback dolphins Sousa chinensis in Hong Kong (HK) waters are part of a large (ca. 2000−2500), but declining, population that occurs in the Pearl River Estuary of southern China. To understand the factors that may influence dolphin densities in 4 different parts of HK, a 25 yr (1996−2020) database containing 66 439 km of line-transect survey effort and 4052 dolphin sightings was used. Seventeen variables representing natural and anthropogenic habitat factors were evaluated using generalized additive models (GAMs) to identify the preferred habitat of humpback dolphins in HK waters. In the environmental GAMs, rainfall, salinity, and river discharge were significant factors related to dolphin density, consistent with their observed strong preference for estuarine habitat. Sea surface temperature was also important for one of the 4 subareas. In the anthropogenic GAMs, the only significant variable was the amount of habitat area lost to land reclamation in North Lantau. This finding is consistent with previous hypotheses that heavy coastal engineering in North Lantau has contributed to observed declines in dolphin abundance during the study period. This study provides some of the first quantitative indications of factors that are potentially influencing the density of the animals in various parts of HK. As such, it will be a valuable tool for evaluating and mitigating potential impacts of both natural and anthropogenic factors on the population in the future. The paper is open access. PDFs can be obtained here: https://www.int-res.com/articles/esr2023/51/n051p143.pdfTom Jefferson ___ MARMAM mailing list MARMAM@lists.uvic.ca https://lists.uvic.ca/mailman/listinfo/marmam
[MARMAM] New Paper Available
Dear MARMAMers, I am pleased to announce the publication of the following paper: Jefferson, T. A. (2023). Marine mammals of the United States Exploring Expedition, 1838–1842: history and taxonomy. Archives of Natural History, 50, 101-117. https://doi.org/10.3366/anh.2023.0831ABSTRACT: The United States Exploring Expedition of 1838–1842, in some ways, represents the beginning of American marine mammal biology. The expedition returned home with information on at least twelve marine mammal specimens (mostly small cetaceans or pinnipeds), seven of which were considered new species at the time. Commanded by Lieutenant Charles Wilkes, the expedition covered over 80,000 miles, surveyed new waters and lands, and brought back thousands of scientific specimens. Official publications of the expedition by Titian Peale and John Cassin cover the birds and mammals collected. The squadron’s publications, and the journals of its officers and scientists also contain a good deal of information about sightings of marine mammals. Of particular interest were whaling operations and grounds, and the expedition did much to help expand the whaling prospects of the United States around the globe, with a focus on the South Pacific islands. Though largely forgotten today, the “U. S. Ex. Ex.” played an important early role in establishing American influence in marine mammal biology and global whaling operations. PDFs can be purchased online, or requested from me (sclym...@aol.com).Tom Jefferson ___ MARMAM mailing list MARMAM@lists.uvic.ca https://lists.uvic.ca/mailman/listinfo/marmam
