Spatial and Temporal Patterns of Movement and Habitat Utilization of Adult and Juvenile Leopard Sharks in Elkhorn Slough, California	Photo: Monterey Bay Aquarium
Aaron Carlisle email: acarlisle@mlml.calstate.edu

Shallow, highly productive areas such as coastal embayments and estuaries are known to be important foraging areas for sharks and rays. In addition to their importance in feeding, a number of studies show shallow estuaries and bays as nurseries are used by neonate and juveniles sharks and rays of many species because of lower rates of predation (due to their inaccessibility to large predators), high abundance of prey items, and the generally warmer waters that may be conducive to rapid growth and improved physiological rates.

Elkhorn Slough, California is an estuary that is utilized by a number of elasmobranchs, with leopard sharks (Triakis semifasciata) being the most abundant. Leopard sharks utilize Elkhorn Slough throughout their life history for feeding, mating, pupping, and as a nursery ground. However, the dynamics of Elkhorn Slough have been and continue to be greatly impacted by human activities. The extensive mudflats, salt marshes, and tidal creeks that they use so extensively are being dramatically altered through erosion and other changes brought about by a number of events such as the installation of the Moss Landing harbor jetties, dredging of the mouth of the harbor, breaching of dykes inside the slough, farming, the 1989 Loma Prieta earthquake, etc… This potential loss of critical habitat is made more worrisome due to the lack of basic information about how the leopard shark moves about and utilizes this environment. My research involves using acoustic telemetry techniques to explore patterns of movement and habitat utilization of leopard sharks inside Elkhorn Slough, California. Both active manual tracking and passive tracking techniques will be used in this project. Actively tracking a shark using a mobile surface tracking system allows data to be collected on short term movements and habitat use, while passive tracking techniques allow for longer term patterns in movement and habitat utilization to be monitored by placing an array of receivers around the slough. Movements will be examined to assess sex and age differences in patterns of movement and habitat use, in addition to patterns for the species as a whole in Elkhorn Slough.

Because of the potential loss of critical habitat, their susceptibility to overfishing and the fact that they are a species that is targeted by commercial and recreational fisheries, it is important to learn as much as possible about how they use an area like Elkhorn Slough, which is likely to be so important throughout their life history (such as functioning as a breeding and nursery ground), in order to better manage and protect the species. I hope that this information will provide managers with information that will allow them to protect critical areas of the slough by identifying potential Essential Fish Habitat (EFH) and assist in the management of the species as a whole.