The Revillagigedo Archipelago is located 250 nautical miles south of the Baja California Peninsula, in the Mexican Pacific Ocean. it comprises of three volcanic islands and one islet: Socorro, San Benedicto, Clarion and Roca Partida and in total they occupy a surface area of 148,000 km2. In 1994, the Archipelago was established as a Natural Protected Area under the national classification as a Biosphere Reserve. In 2002, the Mexican government banned commercial fishing within 9 nautical miles around the four islands and UNESCO declared it a world heritage site in 2016. In 2017, the marine protected area was expanded and now covers of a total 14 million hectares of waters surrounding the islands. These islands host a great terrestrial and marine biodiversity, with 16 endemic species of fish present in the area, sea turtles’ nesting sites, 18 species of marine mammals and a great elasmobranchs diversity, with 28 species of sharks recorded in the archipelago.

Project overview:

The Revillagigedo Archipelago is a marine predator refuge in the Mexican Pacific. It is a habitat of utmost importance that contains one of the richest insular shark faunas in the Eastern Tropical Pacific, where you can observe up to five different species in a single dive.

We are carrying out different studies at the Revillagigedo islands with the following overarching goals:

- Understand movement patterns, inter-island connectivity, and residency of sharks and rays using acoustic and satellite telemetry

- Examine abundance, diversity and behavior of sharks and rays using Baited Remote Underwater Video Systems (BRUVS) and underwater surveys

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

Activities:

1. Ultrasonic tagging. We affix ultrasonic transmitters on different species of sharks at each island. 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 incision.

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 archipelago. We have 14 listening stations distributed in the four islands of the archipelago.

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 silky, hammerhead and tiger sharks.

4. BRUVS. We use benthic (bottom) BRUVS at or near cleaning stations to record the behavior and diversity of sharks visiting this important habitat. We also use pelagic (midwater) BRUVS to study the abundance and diversity of sharks in open water.

5. Genetics. Using SCUBA, we collect skin biopsies for genetic analysis, with the goal of identifying differences between populations in Revillagigedo and the Gulf of California.

Other institutions participating in this Project:

- Centro Interdisciplinario de Ciencias Marinas-IPN

- Florida International University

- MigraMar

- University of California, Davis

Species under investigation: