Abstract

The vaquita (Phocoena sinus) is a small porpoise found only in the northern Gulf of California. This species may have been subject to high levels of mortality in the gill-net fishery for totoaba (Totoaba macdonaldi) in the 1960s and early 1970s (prior to a ban on totoaba fishing). Incidental fishing mortality continues to be associated with shark gill-net fishing and illegal totoaba fishing. Based on its limited range and history of incidental mortality, several national and international organizations have concluded that P. sinus is in danger of extinction, and the species is included in the list of U.S. Endangered Species. Little is known about the species. Food sources include small fish and squid. Sightings have occurred most commonly in water from 13 to 18 m deep. No population estimates have been made to date, and the present and historical range of the species is currently the subject of debate. Researchers who have conducted surveys agree, however, that the species is rare. Insufficient information exists to estimate population growth rates, but based on comparisons to closely related species, the maximum annual rate is probably less than 10%. The actual rate of growth is less (and may be much less) due to continued fishing mortality and possible habitat modifications. Given available information and current survey technology, it will be many years before researchers can determine whether population size is increasing or decreasing.