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FIRST ESTIMATES OF VAQUITA ABUNDANCE
Author(s) -
Barlow Jay,
Gerrodette Tim,
Silber Greg
Publication year - 1997
Publication title -
marine mammal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.723
H-Index - 78
eISSN - 1748-7692
pISSN - 0824-0469
DOI - 10.1111/j.1748-7692.1997.tb00611.x
Subject(s) - porpoise , phocoena , abundance (ecology) , aerial survey , transect , population , biology , cetacea , geography , fishery , ecology , environmental science , cartography , demography , harbour , sociology , computer science , programming language
A bstract 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.