Marine mammal monitoring in the Southwest Pacific State of Guerrero, Mexico

Marine mammal diversity, abundance and habitat use data are lacking in the southwestern Pacific state of Guerrero, Mexico. Aggressive behavior from fishing and tourist boats toward marine mammals, exacerbated by the absence of monitoring and enforcement underlies the need for a better understanding of species present. Our intended five-year study aims to document presence/absence of marine mammals, to establish patterns of spatio-temporal habitat use and to identify sensitive marine mammal areas in the interest of improved ecosystem management.

Between January-March 2014-2017, we conducted 200 boat surveys (1303 hours), covering 50 coastal miles surrounding Ixtapa-Zihuatanejo and extending 10 NM to sea. Our focal species were humpback whales; we collected data on other marine mammals and large marine fauna opportunistically. We sampled acoustically every 30 minutes, recorded behaviour and noted resightings inter- and intra-annually. Community members participated in field studies and public educational programs to foster responsible marine stewardship.

Cumulative species count results are: Megaptera novaeanglie (354), Balaenoptera edeni (5), Steno bredanensis (109), Stenella attenuata (403), Tursiops truncatus (35), Stenella longirostris (3), Delphinus delphis (4), Grampus griseus (1), Globicephala macrorhynchus (1), Kogia sima (1), Ziphius cavirostris (1) and Arctocephalus townsendi (2). High percentage of humpback whale calves (11%; 69/611 total animals), courting activity, and frequently detected singing (singing detected 82/181 days; 45%) indicate that Guerrero is a breeding area for this species. Photo-identification matches with other regions suggest that Guerrero humpback whales may be more affiliated with the endangered Central America Distinct Population Segment (DPS) than the main Mexico DPS. 151 individual rough-toothed dolphins have been re-sighted. Interim results show that Guerrero contains significant marine mammal diversity and may include areas of aggregation for multiple species. Final results, along with our concurrent outreach and educational programs will help guide monitoring, protection recommendations and support improved marine resource management in this unregulated region.


Garcia Chavez, A., T. Hanks, J. Calambokidis, E. Dobson, K. Audley. 2017. Marine mammal monitoring in the Southwest Pacific State of Guerrero, Mexico. Abstract (Proceedings) 22nd Biennial on the Biology of Marine Mammals, Halifax, Nova Scotia, October 22-27, 2017.

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