Sea of Cortez shorelines

Modified from NOAA-NGDC image, data from Thomson et al, 1979.	Shoreline substrates of the Sea of Cortez The map at left shows the extent of Rocky shorelines (in red) within much of the Sea of Cortez (between white arrows, which excludes most of the Pacific coast of the Baja California peninsula and the mainland south of Topolobampo). The other shorelines are generally sandy beaches or mudflats. However, within the area shown as rocky shoreline, there are numerous small sandy beaches, especially in coves between rocky headlands. The type of substrate is a major determinant of which species of organisms inhabit an area. Intertidal and subtidal organisms in sandy or muddy substrates are commonly burrowing forms, which often have specific requirements for certain grain sizes. There are usually fewer epibenthic forms in these fine grained substrates. In contrast, rocky reef and rocky intertidal areas are usually dominated by epibenthic forms, although many can be found in crevices and under rocks, and a few forms actually burrow into softer rocks. Benthic fishes usually show a strong preference for certain substrate types, and even midwater and surfacewater fishes show preferences for areas with a certain substrate type.

	At above left is a typical coastal area near San Carlos, on the Mexican mainland (shown in red on map at left). This is a rocky shore, mostly of bedrock, and is similar to many areas of rocky shoreline all around the Gulf. Above right is another shoreline not far away, but this is a predominately rocky area, and there is a sizeable sand-gravel beach at this location.

	At above left is a typical rocky shoreline of soft bedrock near Cabo Pulmo, in the southeastern corner of the Baja California peninsula, (shown in red on map at left). Above right is a rocky headland near the same area, surrounded by sizeable sand-gravel beaches.

	At above left is an extensive mudflat at Cholla Bay, north of Puerto Penasco at the northern end of the Gulf (shown in red on map at left). This mudflat is several kilometers across, and is in an area with some of the largest tides in the world, with 20 to 30 feet of vertical displacement (Brusca, 1980). Above right is a tractor at Puerto Penasco, modified so that it can pull boats out on the mudflats into deep enough water for launching (when the tide is high).