Distribution of the acoustic occurrence of dolphins during the summers 2011 to 2015 in the Upper Gulf of California, Mexico

Gustavo Cárdenas Hinojosa; Horacio de la Cueva; Tim Gerrodette; Armando M Jaramillo-Legorreta

doi:10.7717/peerj.9121

Distribution of the acoustic occurrence of dolphins during the summers 2011 to 2015 in the Upper Gulf of California, Mexico

PeerJ. 2020 May 20:8:e9121. doi: 10.7717/peerj.9121. eCollection 2020.

Authors

Gustavo Cárdenas Hinojosa^{1

2}, Horacio de la Cueva¹, Tim Gerrodette³, Armando M Jaramillo-Legorreta²

Affiliations

¹ Departamento de Biología de la Conservación, Centro de Investigación Científica y de Educación Superior de Ensenada, Ensenada, Baja California, México.
² Comisión Nacional de Áreas Naturales Protegidas, Secretaría de Medio Ambiente y Recursos Naturales, Ensenada, Baja California, México.
³ Southwest Fisheries Science Center, National Oceanic and Atmospheric Administration, San Diego, CA, United States of America.

Abstract

Baseline knowledge of spatial and temporal distribution patterns is essential for cetacean management and conservation. Such knowledge is particularly important in areas where gillnet fishing occurs, as the Upper Gulf of California, which increases the probability of bycatch of cetaceans. In this area, the vaquita porpoise (Phocoena sinus) has been widely studied, but the knowledge of other cetaceans is scarce and based on traditional visual survey methods. We used data collected by an array of acoustic click detectors (C-PODs) during the summers 2011 to 2015 to analyze the distribution of dolphins in the Vaquita Refuge in the Upper Gulf of California. We recorded 120,038 echolocation click trains of dolphins during 12,371 days of recording effort at 46 sampling sites. Based on simultaneous visual and acoustic data, we estimated a false positive acoustic detection rate of 19.4%. Dolphin acoustic activity varied among sites, with higher activity in the east of the Vaquita Refuge. Acoustic activity was higher at night than during the day. We used negative binomial generalized linear models to study the count of clicks of dolphins in relation to spatial, temporal, physical, biological and anthropogenic explanatory variables. The best model selected for the response variable included sampling site, day-night condition, and vertical component of tide speed. Patterns in the spatial distribution of predicted acoustic activity of dolphins were similar to the acoustic activity observed per sampling season. Higher acoustic activity was predicted at night, but the tide speed variable was not relevant under this condition. Acoustic activity patterns could be related to the availability of prey resources since echolocation click trains are associated with foraging activities of dolphins. This is the first study of the distribution of dolphins in Mexico using medium-term systematic passive acoustic monitoring, and the results can contribute to better management to the natural protected area located in the Upper Gulf of California.

Keywords: C-Pod; Echolocation clicks; Generalized linear model; Natural protected areas management; Passive acoustic monitoring; Vaquita refuge.

Grants and funding

This work was supported by CICESE, WWF-Mexico, U.S. Marine Mammal Commission, Le Equipe Cousteau, The Ocean Foundation, Fonds de Dotation pour la Biodiversité, MAAF Assurances (Save Your Logo), WWF-US, Opel Project Earth, Secretaria de Medio Ambiente y Recursos Naturales (SEMARNAT), the Instituto Nacional de Ecología (INE), and the Comisión Nacional de Áreas Naturales Protegidas (CONANP). Gustavo Cárdenas Hinojosa received a scholarship granted by CONACYT (Num. 165214/165214) for the CICESE Ph.D. program and a research grant by The Rufford Small Grants Foundation for funding the field trips to collect simultaneously visual and acoustic data of dolphins. There was no additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.