Sea of Cortez fieldtrip overview

Modified from NOAA-NGDC image

The Sea of Cortez and the Baja California peninsula

Overview

The Sea of Cortez is a partially enclosed sea that lies between the Baja California peninula and the Mainland of Mexico. In 1540 the Spanish explorer Francisco de Ulloa named it El Mar de Cortes (the Sea of Cortez) after his leader, Hernan Cortez. However, the official name is El Golfo de California (the Gulf of California). Here we will use these two names for the sea interchangeably.

The Baja peninsula is the second longest isolated peninsula in the world, only the Malay peninsula is longer. The peninsula extends over 1,070 km (about 700 miles) in a southeastward direction from its attached base on the west coast of the North American continent, and varies in width from about 100 to 200 km. The Sea of Cortez between the Mainland and the peninsula is relatively narrow, but extends from warm temperate areas in the north to the tropics in the south. It therefore has a great diversity of organisms within this ten degree span of latitude, changing significantly from the northern end to its southern limits. The sea was originally much longer as it extended northward, but Colorado River sediment deposits have dammed off the northern end, forming what is now Imperial Valley, California.

Because the coastal areas on both sides of the sea are mostly arid with few resources for development, the area surrounding the Gulf has been relatively unspoiled by human activities. The islands within the Gulf are probably one of the most pristine archipelagoes left on earth. They are consequently of enormous biological and ecological value, with the Sea and its islands considered a great natural laboratory for the investigation of speciation and island biogeography. (Case and Cody, 1983).

The Colorado river flows into the northern end of the Gulf, however its inflows have been reduced enormously during the 20th century by water diversions to the growing populations of Arizona and Southern California. Increased commercial fishing pressure and agricultural development in surrounding coastal areas threaten the pristine state of the Sea of Cortez, and in the last few decades there has been a substantial decline in the distribution and abundance of many species.