Vaquita Autonomous Acoustic Monitoring Development Cruise
Artwork by Barbara L. Taylor
Vaquitas are a critically endangered porpoise found only in a small part of the Upper Gulf of California, Mexico. This porpoise has the smallest distribution of any marine mammal. Recent acoustic data indicating a decline in vaquita numbers taken together with the probable extinction of the Chinese River dolphin prompted the government of Mexico to take unprecedented steps to save their porpoise from the same fate: extinction resulting from accidental deaths when animals drown in fishing nets.
The recently concluded Vaquita Expedition 2008 was a joint US-Mexican effort to provide the best scientific data possible to aid the government of Mexico in conservation decisions for the vaquita. The primary goal was to use passive acoustics to see whether conservation actions to reduce the level and area of gillnetting are allowing vaquita numbers to increase. Three vessels were used: the Koipai Yú-Xá, which has been the primary acoustics research vessel for Mexico and lead the work on stationary acoustic research, the Vaquita Express, a 24 foot (9m) sailing vessel that towed an acoustic array, and United States NOAA Ship David Starr Jordan, which deployed research buoys for autonomous acoustic recorders, conducted oceanographic work to better understand vaquita habitat and carried out visual surveys. Scientists came from Mexico, the US, Canada, United Kingdom, Japan, Germany, Australia and South Africa.
The inventors of the acoustic equipment used to detect porpoises came to the Upper Gulf of California so that they could modify their equipment for this expedition. They discovered that the Upper Gulf of California was very noisy in the high frequencies used by vaquita to echolocate. Despite the challenges, all three types of vaquita detectors successfully detected vaquita. The array towed by the sailboat also detected vaquitas in very shallow water close to one of the main fishing villages. The acoustic detections confirm the good news also seen by the visual team using high powered binoculars: vaquita are not extinct and their distribution is roughly the same as it was ten years ago.
However, data from the research buoys show great differences in vaquita densities within their known range. Some buoys detected no vaquitas in the two month research period, while other buoys detected vaquitas almost daily. Scientists will use these data to design an acoustic monitoring program which will determine whether the current conservation actions to reduce gillnet mortality are being successful.
The Instituto Nacional de Ecología (INE), SEMARNAT, is the Mexican partner in the Vaquita Expedition 2008. Learn more about INE vaquita research http://www.ine.gob.mx/dgioece/con_eco/bitacora_vaquita.html.
US Chief Scientist: Barbara L. Taylor, PhD
Mexico Chief Scientist: Lorenzo Rojas-Bracho