The Influence of Environmental Variables on the Distribution and Abundance of Three Elasmobranchs in Tomales Bay, California |
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Authors: | Todd E. Hopkins Joseph J. Cech Jr |
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Affiliation: | (1) Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, USA;(2) Present address: US Fish and Wildlife Service, South Florida Ecological Services Office, 1339 20th Street, Vero Beach, FL 32960, USA |
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Abstract: | We tested the hypothesis that temperature, salinity, and dissolved oxygen affect elasmobranch distribution and abundance in Tomales Bay, California, with monthly longline samples over a 20 month period. We used a Poisson regression under generalized least squares and found that temperature and salinity were the most important factors determining the distribution and abundance of the three most common elasmobranch species, bat ray, Myliobatis californica, leopard shark, Triakis semifasciata, and brown smoothhound shark, Mustelis henlei. Females of all three species were more abundant than males throughout the Bay, and were most abundant in the warmer, more saline inner bay. All three species apparently left Tomales Bay in late fall as water temperatures in the bay decreased to <10–12° C, and returned in early spring after temperatures increased to > 10° C. Three of 257 bat rays tagged in Tomales Bay were recaptured, all within 1km of their tagging location despite having been free for up to 583d. |
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Keywords: | bat ray Myliobatis leopard shark Triakis brown smoothhound Mustelus |
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