Sea of Cortez biogeography

Marine Biogeography of the Sea of Cortez and the Pacific Coast of Baja California

There are two regions for this general area, the Eastern Warm Temperate region in the north, and the eastern tropical Pacific region in the south.

The actual boundaries of these regions, provinces, and areas depend to some extent on the taxa considered and the investigator describing the area, although the broad patterns of distribution are often similar. The map at left and the regions described are based on the NOAA (1990) data atlas, and are used here as one example of a classification scheme of biogeographic areas.

The Eastern Warm Temperate Region includes two provinces:

The San Diegan Province includes the Pacific Coast of the Baja California peninsula. This province includes two areas:

The Southern Coast area
This area is strongly warm temperate without much coastal upwelling, and the fauna resembles that of the Southern California bight. However, the southernmost of these subareas, from Laguna San Ignacia to Magdalena Bay, has many tropical species as well (Hewit, 1981).

The Baja California upwelling area
This is an area of strong coastal upwelling, with many species more typical of the Central California and Oregon coasts.

Cortez Province includes the Sea of Cortez coast north of tropical waters. In general, the entire Sea of Cortez is primarily tropical in origin, and subtropical presently (Brusca, 1980). As with other subtropical regions throughout the world, it represents a gradient of more tropical species in the south, to a northern fauna of fewer (and more eurythermal) tropical species. This province includes two areas:

The Upper Gulf area
This area is strongly warm temperate with cooler winter temperatures. The temperatures in summer can be quite warm, with relatively cold winter temperatures. Accordingly, this area contains relatively eurythermal species of mostly tropical origin.

The Middle Gulf area
This is a transitional area, with increasing numbers of tropical species occuring as one moves southward. At the southern edge of this area the fauna is largely tropical in character.

The Eastern Tropical Pacific Region includes the Panamic Province , which extends southward to Ecuador. This area contains primarily tropical species.