Cetaceans Research Papers - Academia.edu (original) (raw)

Interest in the study of Mexican marine mammals dates from the
mid-nineteenth century, a result of their commercial exploitation. Nevertheless, until the 1970s scientifi c studies of the marine mammals of Mexico were infrequent and mainly limited to occasional observations by American and a few Mexican scientists. Beginning in the late 1970s, the number of reports published on individual species or groups of species in the Gulf of California began to increase substantially.
The marine mammal fauna of the Gulf is surprisingly diverse, with
36 species representing 31 cetaceans in eight families (Balaenidae, Eschrichtiidae, Balaenopteridae, Physeteridae, Kogiidae, Ziphiidae, Delphinidae, Phocoenidae), four pinnipeds in two families (Phocidae, and Otariidae), and one bat in the family Vespertilionidae. The Gulf of California has 39 percent of the world’s 83 cetacean species. The Odontoceti (toothed whales) are represented by 23 species, 33 percent of the extant species, and the Mysticeti (baleen whales) by 8 species, 61 percent of the extant species. The notable diversity (i.e., species richness) and abundance of marine mammals in the Gulf can be explained by three main factors. First, the Gulf has an exceptionally high rate of primary productivity that supports complex and productive food webs. Second, the complex topography and oceanography of the Gulf presents a high diversity of habitats. And third, the warm and relatively calm waters found in the Gulf during winter and spring are exploited by several migratory species to give birth, nurse, and care for their newborn.
According to the IUCN, the Gulf of California includes one species
that is critically endangered (vaquita), four that are endangered (bluewhale, fi n whale, sei whale, northern right whale), and two that are vulnerable
(humpback whale, sperm whale). The Mexican Government’s Offi
cial Standard (NOM-59-ECOL-2001) includes all of the cetacean species
entering Mexico’s waters. The North Pacifi c right whale and the vaquita
are listed as “in danger of extinction” and all others as “subject to special
protection.” The main human-caused mortalities of cetaceans in the Gulf of California are related to fi sheries. The cetaceans most frequently involved in incidental mortality from fi sheries are the short-beaked common dolphin, long-beaked common dolphin, common bottlenose dolphin, pantropical spotted dolphin, and vaquita. Yet large cetaceans, including sperm, gray, and humpback whales, also have been affected by fi sheries. There is no single body of legislation enacted for the sole benefi t of cetaceans in the Gulf. Instead there are several different laws relevant to their conservation and management that apply to all of Mexico. Additionally, in May 2002, Mexico established the Mexican Whale Refuge (Refugio Ballenero Mexicano), consisting of its entire Exclusive Economic Zone (about 3 million km2).