Clipperton Island is an uninhabited coral atoll in the eastern Pacific Ocean off the coast of Central America, with a surface area of 6 km2. It is an overseas minor territory of France, under direct authority of the Minister of Overseas France. Clipperton’s nearest landmass is Socorro Island in the Revillagigedo Archipelago of Mexico, which is about 1,000 km north. The islands structure is generally low-lying and for the most part barren, with some scattered grasses and a few clumps of coconut palms, with one small volcanic rock on its south-east side referred to as "Clipperton Rock". Clipperton does not have permanent inhabitants, receiving occasional visits by fishermen, French Navy patrols, and scientific researchers who come to study its untouched coral reef structure.

Project overview:

Clipperton Atoll is the most isolated and most westerly coral reef in the Eastern Tropical Pacific (ETP). Clipperton is the only atoll in the ETP and its 3.7 km2 coral reef is the largest in the region, considered a cross-roads for the migration of fish both northwards and southwards. Given the isolation of this rich habitat it has provided a safe haven for a number of shark species to thrive.

We are carrying out different studies at the Clipperton Atoll with the following overarching goals:

- Understand movement patterns and residency of sharks using acoustic and satellite telemetry

- Examine long-distance movements of sharks north and southwards from the atoll using acoustic and satellite telemetry

- Understand population size and structure, and connectivity of sharks using genetics

- Examine the role of foraging, the trophic niche and mercury levels of juvenile silvertip sharks

Activities:

1. Ultrasonic tagging. We affix ultrasonic transmitters on different species of sharks. We use ultrasonic tags, which emit a specific code that is recorded by acoustic receivers (listening stations). The transmitters are placed externally in the base of the dorsal fin with a Hawaiian sling used for spearfishing by SCUBA or free divers. Transmitters are also put internally in the intraperitoneal cavity through capture and a small surgery.

2. Listening stations. The stations consist of an underwater receiver VR2W (Vemco Ltd) that records acoustic pulses from the ultrasonic tags in a maximum range of 500 m. The stations are placed at depths between 20 and 40 meters at shark aggregation sites and cleaning stations in the atoll. We have 3 listening stations distributed in the atoll.

3. Satellite tagging. Satellite transmitters are designed to track the large-scale movements and behavior of fish and sharks. These transmitters are equipped with light, temperature, depth and accelerometer sensors, that either archives data in an on-board memory or transmits during deployment. We are deploying satellite transmitters in Galapagos and silky sharks.

4. Genetics. We collect skin biopsies for genetic analysis, with the goal of identifying differences between shark populations in the Eastern Tropical Pacific.

5. Stable Isotope and Heavy Metal analyses. Using Carbon (δ13C) and Nitrogen (δ15N) stable isotope analysis as well as total mercury (THg) concentrations we want to assess the role of foraging site on the trophic niche and THg levels of juvenile silvertip sharks.

Other institutions participating in this Project:

- Center for Insular Research and Observatory of the Environment (CRIOBE)

- Fundación Malpelo

- MigraMar

Species under investigation: