FIRST ESTIMATES OF VAQUITA ABUNDANCE

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, t...

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Bibliographic Details
Main Authors: Barlow, Jay, Gerrodette, Tim, Silber, Greg
Format: Text
Language:unknown
Published: DigitalCommons@University of Nebraska - Lincoln 1997
Subjects:
vaquita
Gulf of California harbor porpoise
Phocoena sinus
abundance
population
line-transect survey
trends
endangered species
Mexico
Environmental Sciences
Phocoena phocoena
Online Access:https://digitalcommons.unl.edu/usdeptcommercepub/234
https://digitalcommons.unl.edu/context/usdeptcommercepub/article/1233/viewcontent/Barlow_MMS_1997_First_estimate_Vaquita.pdf
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Summary: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 in dicates 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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