Barlow, J., T. Gerrodette, and G. Silber. 1997. First estimates of vaquita abundance. Marine Mammal Science 13(1): 44-58.
*Southwest FIsheries Science Center, P.O. Box 271, La Jolla, CA 92038 USA
The abundance of the only population of vaquitas, Gulf of California harbor porpoise (_Phocoena sinus_), is estimated from four surveys conducted in Mexico between 1986 and 1993, using a variety of methods. A line-transect approach was applied, using some parameters estimated from a related species, the harbor porpoise (_Phocoena phocoena_). Vaquita abundance is estimated as 503 (CV = 0.63) from 1986-1988 boat surveys, 885 (CV = 0.50) from 1988-1989 aerial surveys, 572 (CV = 1.43) from a 1991 aerial survey, and 224 (CV = 0.39) from a 1993 ship survey. A weighted log-linear regression indicates a rate of population change (decline) of -17.7% per year (95% CI = -43.2% to +19.3%) between 1986 and 1993. All of these estimates of vaquita abundance indicate that the species is at a critically low level.