(…) During April 1997 the acoustic detector was successfully used to detect vaquitas for the first time. On that occasion we surveyed on a fixed location, aboard an outboard motor skiff boat (panga), only during daylight hours. The sampling effort on fixed stations was similar to the one applied later on (starting in 2001). The panga was anchored in a spot (with the motor turned off and the acoustic detector deployed and operating at all time) near San Felipe Bay (Figure 1) under daylight conditions during five consecutive days, totaling 31 hours of effort. Since June 2001, up to April 2007, we have completed more than 790 hours of effective effort acoustically surveying for vaquitas in 63 fixed points. This effort has been spread along the potential areas of distribution, in the upper and northern Gulf of California. However, vaquitas have been detected only in front of the coast of Baja California, near San Felipe harbor, a fishing and touristic town (Figure 1).
In this report we present the trend of the acoustic detection rate (number of confirmed acoustic encounters of vaquita groups / effective effort) in this area and discuss its meaning for vaquita current status and recovery plans. (…)