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
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