Marine ecorregions in Mexican Pacific Transition

The Mexican Pacific Transition is a fairly complex region, with a narrow shelf that drops off steeply to great ocean depths close to the coast. It is incised by several canyons and the Mesoamerican Trench that plunges to depths between 4,000 and 5,000 m. In addition, the region is dotted by numerous submarine hills and mountains, and includes a rift system and volcanic cones that have emerged from the depths of the ocean. It also has a great diversity of coastal systems and subsequently high species diversity. Tourism has contributed to shaping many of the coastal communities in the region. The Mexican Pacific Transition is a tropical sea that is seasonally affected by the winter influence of the California Current. Waters off the Mexican states of Jalisco, Colima, Michoacan, Guerrero and Oaxaca and the southernmost tip of Baja California Sur are included in this region. The northernmost limit of this region, in general coincides with where the California Current turns westward in summer, leaving the region under the influence of the warm Costa Rica Coastal Current.

Rationale: Encompasses the southernmost winter influence of the California Current; its northernmost limit, in general coincides with where the California Current turns westward in summer, leaving the region under the influence of the warm Costa Rica Coastal Current.

Major community types and subtypes: Rocky shores, sandy shores, coastal lagoons, estuaries, generally small deltaic systems, reef patches and mangroves, and deep-sea communities.

Species at risk: Loggerhead sea turtle, East Pacific green sea turtle, leatherback sea turtle, and olive ridley sea turtle. Species like the silky shark, scalloped hammerhead, and smooth hammerhead are presenting signs of overfishing from artisanal shark fisheries targeted at immature individuals. Offshore fisheries may be impacting species with low fertility rates such as the pelagic thresher and bigeye thresher. Other species of concern include the whale shark, great white shark, sawfish, and mantas (giant manta, spinetail mobula, smoothtail mobula, pygmy devil ray, and sicklefin devil ray).

Human activities and impacts: Fisheries, coastal tourism and urban development.