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Distribution and Abundance
The Vaquita is the only species of porpoise found in such a small
region: the upper Gulf of California. It is found nowhere else
in the world, making it an endemic species of the upper Gulf of
California.
Scientists believe that the Vaquita is part of a fauna that originated
in cool temperate waters, like most porpoise species. They think
the Vaquita was trapped in the upper Gulf during a period of global
warming when tropical waters expanded northward. These warm seas
formed a high temperature barrier for these typically cool water
creatures.
The Vaquita's limited range of distribution was determined by
studying records of animals that were stranded on the beach or
recovered from gill nets and from sightings of live animals. To
confirm this distribution and to estimate the size of the Vaquita
population various efforts have been made to observe live animals.
The last of these, conducted in 1997 by an international team
of researchers, concluded that the geographical distribution of
the Vaquita is restricted to the upper Gulf of California, in
an area to the North of Puertecitos, near Rocas Consag Island
and El Golfo de Santa Clara and around and north of Puerto Peñasco.
Movement within the habitat
A large percentage of Vaquita sightings have been registered in
waters between 21 and 35 meters depth, with visibility ranging
from 0 to 12 meters. All the reports of Vaquitas entangled in
nets come from waters between 4 to 36 meters in depth and within
3 to 33 km of the coast.
Because the turbidity of these waters makes visual detection by
predators and prey alike difficult, scientists believe that the
acoustic sounds produced by the Vaquita help it detect prey near
the sea floor.
Sightings of Vaquita in the upper
Gulf in the fall and in the spring suggest that they occupy the
upper Gulf throughout the year. It is thought that the Vaquita's
small size and their relatively tall dorsal fin may be adaptations
to tolerate the high summer temperatures of the Northern Gulf.
Local distribution seems to be concentrated near San Felipe and
Rocas Consag, as well as near El Golfo de Santa Clara. The presence
of upwelling near Rocas Consag could account for the constant
sightings of Vaquita in this area, as they are possibly being
drawn there to feed..
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