Marine protected areas for whales, dolphins, and porpoises: a world ...

Habitat Protection for Cetaceans around the World 397
along the entire Pacific coast of Central and South America. (Please note that
in oceanographic and biogeographical studies, the Southeast Pacific is usually
considered distinct from Central America, often referred to as the Eastern
Pacific, but we treat both areas together here for consistency with the WCPA
division into 18 marine regions that we have adopted.) Therefore, the Southeast
Pacific features portions of the Pacific subpolar, temperate, subtropical and
tropical waters, the latter two on both sides of the Equator. Notable offshore
islands include the Galápagos Archipelago, Cocos Island and the Juan
Fernández Archipelago. The Southeast Pacific Marine Region has two large
marine ecosystems (LMEs): the Humboldt Current and the Pacific Central-
American Coastal.
The surface oceanography of the northern hemisphere part of the region
is determined by the warm North Equatorial Counter Current which enters the
region at up to 10ºN and splits off Costa Rica, flowing north and south along
the coast and turning into a cyclonic eddy off Panamá and Colombia and an
anti-cyclonic eddy off Nicaragua.
From the south, the cold, nutrient-rich waters of the Antarctic Circumpolar
Current flow toward the southern tip of South America from the west,
branching to the north and south. The northern section splits into the coastal
Humboldt Current and the Peru Oceanic Current, both of which are separated
by the warm, southward-flowing Peru-Chile Counter Current. The key
productive current is the Humboldt Current, which is cold and rich in nutrients
and has numerous gyres that give rise to local countercurrents and upwellings.
The Humboldt Current supports some of the most productive fisheries in the
world off Peru and Chile. Flowing north along the coast, when the Humboldt
Current reaches about 6ºS, it meets and mixes with warm, southward flowing
currents as it veers west, turning into the South Equatorial Current.
The most important alteration in the oceanography of this region comes
from the periodic El Niño event. When this occurs, the warm waters from the
Equator dominate the Humboldt Current causing seawater temperature rises
of 2–3º C and sea level rises of up to 1.6 ft (50 cm), with nutrient levels greatly
reduced in the surface waters. El Niño causes declines in marine life dependent
on these key productive areas of the region, and it is devastating to many local
and commercial pelagic fisheries.
Coral reefs in the region are limited to Central America plus Colombia and
are not nearly so extensive or diverse as on the Atlantic and Caribbean side of
South and Central America. Mangroves extend a little further south to the
border of Ecuador and Peru.
The most dominant factor for offshore cetacean presence is the occurrence
of upwellings that attract feeding baleen whales, as well as various toothed
whales and dolphins. Besides the Humboldt Current, there are large upwellings
in the Gulf of Papagayo, the Gulf of Panamá and seasonal upwellings off the
coast of Chile. The Galápagos upwelling is produced when the west underwater
Cromwell Current meets the westernmost islands, Fernandina and Isabela; this
most productive area of the Galápagos supports a large number of cetaceans,
especially sperm whales and various baleen whales. The Peru-Chile Trench