Colorado River Delta - Ecology

Ecology

The delta supports a variety of wildlife, including several threatened and endangered species. Mexico’s Environmental Regulations on Endangered Species lists the following endangered species found in the terrestrial and aquatic regions of the delta (Diario Officiel, 1994):

• the desert pupfish, also listed as an endangered species in the U.S., the largest remaining population anywhere is in La Ciénega de Santa Clara
• the Yuma Clapper Rail, also listed as an endangered species in the U.S.
• the bobcat
• the vaquita porpoise, the world's smallest marine cetacean, listed as a species of special concern by the U.S. Marine Mammal Commission. There are thought to be less than 250 vaquita left in the world.
• the totoaba, now virtually extinct, a steel-blue fish that grows up to 2m (7ft) and 136kg (300 pounds), and once supported a commercial fishery that closed in 1975 (Postel et al., n.d.).
• the Colorado delta clam, once an extremely abundant species and important in the trophic dynamics of the ecosystem.

Although not extensively studied, the delta’s significance for migratory birds is indisputable, as it is the principal freshwater marsh in the region. A total of 358 bird species have been documented in the Colorado River Delta and upper Gulf of California region. From these, two are listed as endangered, six as threatened, and sixteen are under special protection in Mexico. Two wintering species and five breeding species have been locally extirpated, including the Southwestern Willow Flycatcher, the Fulvous-whistling Duck, and the Sandhill Crane.