25. Alto Golfo de California

Site Overview

The Upper Gulf of California is a unique oceanographic area. This area has some of the largest tides to be found anywhere in the world, with vertical displacement of as much as six to nine meters (20 to 30 feet), while the total depth of the region only reaches approximately 200 meters (650 feet). Sea surface temperatures vary greatly due to seasonal changes, and the waters are highly saline, especially along the shallower coastlines where evaporation rates are high. It is near the mouth of the Colorado River, where hypersaline water from the tidal flats in the region meets the cooler, less saline water from the south. The area is considered an inverse estuary because evaporation exceeds input from precipitation and because of the minimal input of freshwater from the Colorado River.

Coastal strand species are dominated by Atriplex and Ambrosia species, and the endemic pickleweed (Suaeda puertopenascoa) is known only from estuaries in Sonora (Felger 2000). Due to trenches and basins nearby, this area experiences intense upwelling, along with strong tidal mixing, which creates one of the most productive areas in the Gulf of California. Commercial fishing, such as shrimp trawling and hand diving for blue crab (Callinectes bellicosus), is practiced here. This area is characterized by endemic species, among them 22 endemic fish species, including the critically endangered totoaba.

A wide variety of seabirds, such as brown booby, black skimmer (Rynchops niger) and occasionally Heermann’s gull, nest on the islands in the area. Isla Montegue is one of only five known breeding sites for elegant tern (Sterna elegans). The green sea turtle uses the resources in this area for feeding, and juvenile loggerheads are also occasionally seen in these waters following possible migratory paths from as far away as Japan.

The only marine mammal endemic to the Gulf of California is the vaquita, a small porpoise. A recent estimate suggests fewer than 600 individuals remain in the population, restricted to a small area of the upper Gulf north of Puertecitos (30°45'N) (Jaramillo-Legorreta et al. 1999). Eight other marine mammals are found in this region, including the fin whale, bottlenose dolphin and California sea lion.

Despite some local support, funding and available information for management and conservation, destructive coastal land use continues to rise, and conflicts between fisheries and conservation still exist. This is especially true regarding commercial fishing in areas with vaquita. The limited freshwater input from the Colorado River due to high usage upstream by the United States is a major threat to ecosystem stability.