Sharks and Marine Protected Areas in the Eastern Tropical Pacific

The global decline in shark populations over the last few decades has been a key consideration in the development of marine protected areas around oceanic islands. Cocos Island lies in the Pacific Ocean 340 miles from Costa Rica. It is surrounded by a 12 mile area of protected waters where fishing of any kind is not permitted. The Revillagigedo Archipelago is made up of four widely spaced islands 450 miles west of Manzanillo, Mexico. Each island is ringed by core protected waters and a buffer zone. Both locations are widely known for their abundance and diversity of sharks and have been the focus of recent studies of shark movement patterns, using externally placed ultrasonic tags and an array of underwater listening stations deployed at each location and at other locations in the Eastern Tropical Pacific. In cruises to Revillagigedos (November 2010) and Cocos (January 2011), we used a lift to place internal acoustic tags and SPOT5 satellite tags on tiger sharks and silky sharks to study their long distance movement patterns in the region and outside the protected waters. Here, we present the first 100 days of data from these tags. Silky sharks were found to spend less time at the islands, and ranged greater distances – one individual entered the Gulf of California and then swam southeast for over 1000 km and another one moved 700 km to the south. Tiger sharks generally remained close to the island where they were tagged. In particular, those sharks tagged at Socorro Island (Revillagigedo) displayed a preference for the northern coast of the island, and made several short (<5 km) offshore movements before returning to this site. Along with site fidelity data from ultrasonic receivers and tags placed on hammerheads, silvertip, silky, and Galapagos sharks, this information will help us understand the spatial dynamics of sharks in the region, and how the design of marine protected areas can be improved to contribute to the conservation of these key species.