FIRST ESTIMATES OF VAQUITA ABUNDANCE |
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Authors: | Jay Barlow Tim Gerrodette Greg Silber |
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Institution: | Southwest Fisheries Science Center, P. O. Box 271, La Jolla, California 92038, U.S.A.;Marine Mammal Commission, 1825 Connecticut Ave, N.W. #512, Washington, DC 20009, U.S.A. |
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Abstract: | 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. |
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Keywords: | vaquita Gulf of California harbor porpoise Phocoena sinus abundance population line-transect survey trends endangered species Mexico |
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