Tidal movements of female leopard sharks (<Emphasis Type="Italic">Triakis semifasciata</Emphasis>) in Elkhorn Slough,California |
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Authors: | Aaron B Carlisle Richard M Starr |
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Institution: | (1) Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA;(2) Hopkins Marine Station of Stanford University, 120 Oceanview Blvd, Pacific Grove, CA 93950, USA;(3) University of California Sea Grant Extension Program, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA |
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Abstract: | The leopard shark (Triakis semifasciata) is one of the most common species of elasmobranch in California, and uses the shallow bays and estuaries of California extensively
throughout its life history. To examine the role that tides and time of day play on the distribution and movements of leopard
sharks in an estuarine environment, a total of 22 female leopard sharks (78–140 cm TL) were tagged with acoustic transmitters
in Elkhorn Slough, California, USA. Eight sharks were manually tracked for 20–71.5 h, and 13 sharks were monitored for 4–280 days
using an array of acoustic receivers. Overall, the distribution and movements of sharks were strongly influenced by the tides
and to a lesser extent by period of day, although general patterns of movement differed depending on what region of Elkhorn
Slough the sharks were using. In the main channel of Elkhorn Slough, sharks generally moved with the tide, maximizing the
area over which they could forage on a more dispersed prey field. Conversely, leopard sharks within the Elkhorn Slough National
Estuarine Research Reserve regularly swam against strong currents to remain in proximity to the intertidal mudflats. This
high degree of fidelity to a specific region was probably due to an abundance of important prey in the area. These results
indicate that movements, and thus the foraging ecology, of leopard sharks show a high degree of plasticity and are influenced
by tidal stage, tidal current, availability of suitable habitat, and availability and distribution of important prey items. |
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