An exploration of the population characteristics and behaviours of the white shark in Guadalupe Island

Photo credit: © Edgar Becerril

An exploration of the population characteristics and behaviours of the white shark in Guadalupe Island, Mexico (2014–2019): Observational data from cage diving vessels

Omar Santana-Morales | Rebeca Zertuche-Chanes | Edgar M. Hoyos-Padilla | Chugey Sepúlveda | Edgar E. Becerril-García | Juan P. Gallo-Reynoso | Isai Barba-Acuña | Adán Mejía-Trejo | Marc Aquino-Baleytó | Oscar Sosa-Nishizaki | James T. Ketchum | Rodrigo Beas-Luna

Aquatic Conservation: Marine and Freshwater Ecosystems, 31(12), 3480– 3491

DOI: https://doi.org/10.1002/aqc.3734

Abstract

1. In the eastern North Pacific, the Guadalupe Island Biosphere Reserve (GIBR) is one of the most renowned white shark (Carcharodon carcharias) aggregation sites studied to date and an important tourism activity has been developed in the reserve.

2. This study used tourist-based cage diving activities to biologically monitor white sharks from 2014–2019 within the GIBR.

3. The data indicated a gradual increase in the overall abundance of white sharks with an age-structure shift, as young of the year and juvenile sharks were more prevalent during the latter part of the study period (2016–2019).

4. The arrival of young of the year and juvenile white sharks coincided with regional changes in oceanographic conditions off California and Baja California.

5. The arrival of adult female white sharks coincided with the seasonal peak in elephant seal abundance.

6. Records of high-risk white shark behaviours, a shift to sharks of younger ages, and the high prevalence of small individuals during cage diving activities supports the need for the continued revision of operational protocols.

7. This study highlights the importance of white shark biological monitoring to identify threats and challenges to the growing tourism industry and the management of the species in Guadalupe Island and in other aggregation sites.

Keywords: Island, coastal, threatened species, distribution, behaviour, fish