Abstract

The Guadalupe fur seal (Arctocephalus philippii townsendi) is an Endangered Species Act threatened otariid species whose main breeding grounds are located at Guadalupe Island, México. With only one established breeding site and recent increased numbers of malnourished individuals stranding along the U.S. West Coast and Baja California peninsula, this population is vulnerable to the effects of disease epidemics, natural disasters, extreme climatic events, and anthropogenic impacts.^1,2 Thus, monitoring ecological and health parameters is critical. Traditionally, injectable anesthetics have been utilized for immobilization of large otariid species for sample collection, however, some concerns with such techniques include lengthy anesthetic induction and recovery times (potentially predisposing animals to traumatic injury and drowning during the peri-anesthetic period), dosing inaccuracy due to subjective weight estimations, and drug failure due to incomplete injection.^3-7

This study is the first to assess the use of isoflurane gas anesthesia as a sole anesthetic agent in this species. In order to obtain minimally invasive biological samples and place satellite tags, net capture and isoflurane gas anesthesia of 180 free-ranging Guadalupe fur seals (58 pups, 5 yearlings, 63 juveniles, 3 subadults, and 51 female adults) was carried out at Guadalupe Island, México during 2016–2020. This protocol provided rapid induction and recovery times and a lower rate of anesthetic complications (including no deaths) compared to injectable drug combinations reportedly used in other fur seal species.^3-7 Parameters, including disturbance, capture, recovery, and total anesthetic times; isoflurane and oxygen levels; heart and respiratory rates; capillary refill time; and eye position; were assessed across sex, age group, year, and body condition.

Anesthetic induction times were rapid (average 7 minutes), enabling sampling to commence shortly after capture. Heart rate ranged from 80–164 beats per minute (average 118 bpm) and was positively correlated with anesthetic duration, whereas respiratory rate ranged from 1–24 breaths per minute (average 8 bpm) and was negatively correlated with anesthetic duration. Total anesthesia time lasted 14–60 minutes (average 31 minutes) and was dependent on time needed for sample collection and whether or not a satellite tag was placed. Average recovery time was 6 minutes and increased with longer anesthetic duration. Few side effects were observed including mild muscle tremors in 4 individuals, nystagmus in 3 individuals, and apnea requiring intubation and positive pressure ventilation in 6 animals. All seals recovered fully.

This study offers a safe alternative method for obtaining important biological samples and health parameters from Guadalupe fur seals, including affording reduced risk of injury and complication during the peri-anesthetic period, an especially desirable factor when working with animals in remote and topographically challenging field situations.

Acknowledgements

This work was conducted as a collaboration among The Marine Mammal Center (TMMC); Instituto Politécnico Nacional, Centro Interdisciplinario de Ciencias Marinas (CICIMAR-IPN); University of California, Davis; Department of the Navy; NOAA Fisheries, Marine Mammal Laboratory, California Current Ecosystem Program; and Comisión Nacional de Áreas Naturales Protegidas (CONANP), Reserva de la Biosfera Isla Guadalupe. We thank Jeffrey Harris, Donaxi Borjes Flores, María José Amador-Capitanachi, and Geno DeRango for joining us in the field and helping us safely capture and handle the animals, as well as the Mexican Navy, Grupo de Ecología y Conservación de Islas (GECI), and fishermen community for helping tremendously with field logistics. We also thank Commander, U.S. Pacific Fleet; California Department of Fish Game’s Oil Spill Response Trust Fund through the Oiled Wildlife Care Network at the Wildlife Health Center, School of Veterinary Medicine, University of California, Davis; TMMC; CICIMAR-IPN; and NOAA Fisheries for funding this research. This work was conducted under permits issued to Dr. Elorriaga-Verplancken by Secretaría de Medio Ambiente y Recursos Naturales, Secretaría de Gobernación, and CONANP and TMMC Institutional Animal Care and Use Committee protocol number 2018-3.

*Presenting author

Literature Cited

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