The Gulf of California: Biodiversity and Conservation

7. Sea Turtles of the Gulf of California: Biology, Culture, and Conservation

CHAPTER 7 Sea Turtles of the Gulf of California Biology, Culture, and Conservation jeffrey a. seminoff Summary The productive waters of the Gulf of California provide important feeding and developmental habitats for five of the world’s seven sea turtle species. The most abundant species in coastal waters is the green turtle, known locally as the black turtle (Chelonia mydas). The hawksbill turtle (Eretmochelys imbricata) also frequents nearshore waters, although it is more prevalent in the southern Gulf. The olive Ridley (Lepidochelys olivacea ), leatherback (Dermochelys coriacea), and loggerhead (Caretta caretta) may also be present along the coast, but these species are more common in the Gulf’s offshore waters. Exploitation of eggs and turtles for food, degradation of marine and nesting habitats, and incidental mortality relating to marine fisheries have reduced the local populations of all species throughout the region. Industrial-scale exploitation of sea turtles in the region began in the early twentieth century, and hunting was focused primarily on the green turtle. By the 1960s the harvests reached a production peak, primarily for domestic consumption. At the same time, large-scale harvest of nesting females and eggs at nesting beaches, as well as individuals of both sexes from nearshore waters, occurred farther south on the Pacific coast. As it did earlier in other parts of the world, the demand for green turtles, as well as other species, outstripped the ability of these slow-growing animals to regenerate. A total ban on all sea turtle exploitation was declared by a Mexican presidential decree in 1990. Although this legislation set the legal framework for the protection of sea turtles, only recently has there been a perceived decrease in the illegal hunting of these marine species. This has been due largely to a strong network of sea turtle conservation programs throughout the region, centered largely on the Baja California peninsula. This locally 136 / jeffrey a. seminoff based conservation movement augments a regional nesting beach conservation program that has been in place throughout Pacific Mexico since the 1960s. Together, these efforts have contributed to increases in olive Ridley and green turtle populations throughout the region. Unfortunately, the outlook for loggerheads, hawksbills, and leatherbacks is grim, which is mostly due to unabated by-catch in fisheries gear. Recovery for these species may still be possible but the opportunities are rapidly running out. The leatherback in particular teeters at the edge of extirpation in the Pacific Ocean, and immediate and drastic conservation measures are required at remaining nesting sites, feeding areas, and migratory corridors. Rather than rely solely on laws that are difficult to enforce, conservationists in Mexico are embracing education, ecotourism, stronger fisheries management, and other alternative conservation strategies that together could restore all sea turtle species in the Gulf as well as the entire Pacific Ocean. Introduction When the “Albatross” visited San Bartolome on April 11, 1889, a very remarkable catch of green turtle was made. The U.S.S. “Ranger” was there at the same time and a seining party was made up consisting of members of the crew and that of the “Albatross.” In a single haul of a seine 600 feet long we brought ashore 162 green turtles, many of them of large size. Probably half as many more escaped from the seine before it could be beached; there being a continual loss by turtles crawling over the cork lines during the entire time we were hauling it. (Charles Haskins Townsend in “Voyage of the ‘Albatross’ to the Gulf of California in 1911”) When early explorers first set eyes on the Gulf of California, the coastal waters hosted a remarkable abundance of fish, invertebrates, marine mammals, and sea turtles. The populations of many of the most conspicuous species were so healthy that they seemed to be an inexhaustible resource to those who hunted and fished for subsistence or sale to outside markets. Today , however, this former abundance lives only in our collective memory, as decades of exploitation have depleted most of the target species—perhaps none more so than the green turtle (Chelonia mydas). Without a historical Sea Turtles / 137 baseline, it is difficult to believe that during pre-Columbian times sea turtles were the most abundant large vertebrate group in the Gulf of California. Humans have indeed changed the face of the Gulf and its desert shoreline, but the importance of this area for sea turtles has remained. Although some...