Shark research in the Pacific islands off Baja California Sur

By Pelagios Kakunjá

Our most recent shark research expedition was carried out onboard the M/V Storm to the Pacific islands off Baja California Sur in search of sevengill sharks (Notorynchus cepedianus)! This species lives in estuaries and bays from southeastern Alaska to the southern Baja California Peninsula.

Although we weren’t lucky to find sevengill sharks because the weather conditions were difficult, we successfully serviced our array of acoustic receivers and deployed pelagic stereo BRUVS (Baited Remote Underwater Video System).

The underwater receivers record acoustic pulses from ultrasonic tags in a maximum range of 500 m. They are placed at depths between 20 and 40 meters at shark aggregation sites. Every time a previously tagged shark passes nearby it sends a specific code that is recorded by the receiver. This allows us to understand the habitat use and migratory movements of sharks. We got pings from 4 different transmitters and we are now trying to identify what species they are, by collaborating with several scientists working in the Eastern Tropical Pacific using the same technology.

Also, we are happy that we used the pelagic stereo BRUVS system for the first time in the Pacific waters! This is a non-invasive technique that consists of underwater video cameras with bait that are deployed at different areas. The videos obtained are later analyzed in the laboratory to determine diversity and abundance of sharks and pelagic fish.

The Pelagios Team participating in this expedition was: Dr. Mauricio Hoyos (principal researcher), Miguel Grau (coordinator of acoustic receivers and pelagic BRUVS), Abel Trejo (shark tagging coordinator), and students Irene Casanova and Fernanda Raygoza (field work assistants).

Thank you to Ocean Blue Tree for their support to make this possible, and thank you to the M/V Storm crew for all their help during the expedition!

Blog publication date: October 20, 2021