Abstract
The vaquita (Phocoena sinus) is the world’s most endangered marine mammal, found only in the Upper Gulf of California, Mexico. In September 2016 the population estimate was 30 individuals, and the 2017 Acoustic Monitoring Program shows that the decline has continued unabated. Mortality is from drowning in gillnets, most of which are set illegally for endangered totoaba (Totoaba macdonaldi) to supply Chinese markets with swim bladders. Despite a gill net ban, illegal fishing continues, and in spring 2017, three vaquitas were found dead due to entanglement in nets. An ex-situ strategy was requested in 2017 by the Mexican government as a tool to prevent extinction.
The program’s aim was to catch up to 10 vaquitas, house them temporarily in soft-sided enclosures locally, and once catch operations were successful, build a large sanctuary for long-term housing and breeding. Over the summer of 2017, an array of underwater acoustic recording devices was set over the vaquita range to identify areas of echolocation signals. During field operations in October–November 2017, these data guided visual survey effort from boats. Once vaquitas were spotted, gill nets were set in the vicinity of the animals and high speed boats used to herd animals into the nets. Two vaquitas were caught and restrained in two separate sets and temporarily housed in San Felipe, Baja California, MX.
The first vaquita was a 6–8-month-old, 20-kg, female. Following capture, she was transported to a soft-sided indoor pool, then moved to an ocean net pen. During transport, respiratory and cardiac rates were elevated. While housed, the vaquita appeared agitated, and after four hours, due to no apparent calming of behavior, the animal was released close to the capture site. The second vaquita was an adult, non-pregnant female. She appeared stable during capture and transport, but became agitated when housed in the net pen. Due to sudden listlessness, she was given flumazenil and the decision was made to attempt release. During release she ceased breathing, and despite cardiopulmonary resuscitation, she died three hours later. Within an hour of death, tissues were collected for cell culture and ovarian tissue for cryopreservation and potential future gamete culture. Histopathology revealed cardiomyopathy, skeletal muscle degeneration, myoglobinuric nephrosis, and mild pneumonia.
Both vaquitas were given diazepam immediately following capture. Initial dose was 0.2 mg/kg for the juvenile and 0.175 mg/kg for the adult; repeat doses were given for total doses of 0.8 mg/kg and 0.35 mg/kg, respectively. Both animals developed transient symptoms of pulmonary edema (the juvenile had foam from the blow-hole, the adult developed evidence of bilateral alveolar interstitial syndrome detected with ultrasound) which resolved following treatment with furosemide and methylprednisolone. Blood samples from both vaquitas had elevated levels of creatinine kinase (predominantly cardiac isoenzyme) and lactate dehydrogenase. Catecholamine and cortisol levels in the adult female were also high.
These first efforts at capturing and housing vaquitas revealed that the two individuals were highly stressed. Future capture and housing efforts, if any, should focus on mitigation of stress and its effects on these endangered porpoises.
Acknowledgements
We thank the entire VaquitaCPR team, especially Armando Jamarillo Legoretta, Peter Thomas, Barbara Taylor, Randy Wells, Andy Read, Jonas Teilmann, and Mads-Pieter Heide Jorgensen for leading find and catch efforts, and the animal care team Grant Abel, Ricky Rebolledo, Brenda Bauer, Loren Fish, Jenny Meegan, Veronica Cendejas, Whitney Musser, Antonio Ascencio, Ernesto Mendoza, Lupita Esparza, Sacha Stevenson, Nicole Thomas, Kimberly Leroy, Wayne Phillips, Abraham Cardenas, and Jim Antrim. We also thank the Independent Review Panel, the Comit International para la Recuperacion de la Vaquita, the Mexican and U.S governments, the AZA, AMHMAR, and many private donors and supporters.
* Presenting authors