Bull Sharks in Cabo Pulmo

Cabo Pulmo National Park (CPNP), located in the in the southwestern Gulf of California, is one of the most successful marine protected areas in the world, where a large population of bull sharks (Carcharhinus leucas) exists within the park. Historical records about the abundance and distribution of these sharks in the park were scarce but finally we were able to publish the first paper about the movement patterns and residency of bull sharks within this national park.

To understand how these animals use this area, we used devices known as acoustic transmitters that were attached to the sharks externally using a spear gun. Whenever a tagged shark passed near our underwater receiver a time stamp was recorded. Thanks to this technology we found that the bull sharks occurred more frequently in the park From February to April at the coastal receivers, and from July to September at the deep receivers. However, almost no bull sharks were detected during October at both receiver arrays, which coincides with the highest recorded water temperatures. Most bull sharks prefer water temperatures below 28°C and depths from 14 m to 160 m, occupying a wide range of habitats with diverse prey, from shallow to deep reefs.

Our results suggest that females segregate from males probably for reproductive reasons (pupping in another area) or to feed on more energy-rich prey. This study provides information germane to the protection and management of bull sharks in CPNP. The growing popularity of diving with sharks has drawn tourism to CPNP from all over the world in the last decade. Although the coral reef has been the main highlight of the park, diving with bull sharks in natural conditions has become a major attraction that could increase in the next years if proper management is carried out to avoid the negative effects of uncontrolled diving activity near and around their natural aggregations in Cabo Pulmo.