Habitat use, residency, and seasonal distribution of female leopard sharks Triakis semifasciata in Elkhorn Slough, California

Bays and estuaries play important roles in the life history of leopard sharks Triakis semifasciata, yet these coastal environments are among those most impacted by human activity. To better understand habitat use, spatial associations, and ecological roles of leopard sharks in estuarine environments, movements of leopard sharks were studied in Elkhorn Slough, California, USA. A total of 21 female leopard sharks (78 to 140 cm total length) were tagged with acoustic transmitters and tracked from August 2003 to February 2005. Eight sharks were manually tracked for 20 to 71.5 h, and 13 sharks were monitored for 4 to 280 d using an array of acoustic receivers. Female leopard sharks exhibited a high degree of fidelity to Elkhorn Slough. The distribution of tagged sharks changed seasonally and was likely associated with changes in temperature, salinity, and dissolved oxygen. Sharks used the area that comprises Elkhorn Slough National Estuarine Research Reserve (ESNERR) extensively throughout the year, but especially during spring and summer. When sharks occupied ESNERR, their habitat use was tidally influenced, with sharks using low intertidal mudflats extensively when available. Sharks using the main channel tended to remain in subtidal habitats at all tidal levels. These results suggest that efforts to protect important leopard shark habitats in bays and estuaries should focus on preserving and restoring intertidal mudflats.