The most productive areas of the Southern California coastal eco- 

 systems are the marshes, bays, estuaries and mudflats. Accounts of the 

 most significant of these areas, the rare and endangered species they 



support, and estimates of resident wildlife, are included later for each 



14 

 county. 



Sandy beaches form 75% of lower California's 203 mile-long coast. 

 The characteristics of the beaches vary from season to season and year 

 to year depending on currents, storms, changes in offshore bottom topo- 

 graphy, and man-made influences such as breakwaters. Ampipods and 

 isopods scavenge in the intertidal habitat of the shore. Sand crabs, 

 Emerita analoga , are seasonal organisms which inhabit the surf zone. 

 Extremely abundant, sand crabs provide food for several species of 

 fish. The bean clam, Donax gouldii , is also found in the surf zone 

 sand in large numbers. At depths beyond the coastal surf zone to 35 

 feet, a number of larger organisms form communities frequently based 

 on aggregates of sand dollars, Dendraster excentricus , and in some 

 cases various species of clams. 



Below 35-foot depths, the bottom slopes gently seaward, except in 

 regions of canyons. This sloping bottom is the habitat of clams, snails, 

 worms, crabs, sea pens, flatfishes, rays, perch, and croakers. Depths 

 of 60 to 600 feet support populations of nudibranchs, sea cucumers, 

 starfish, sea urchins, brittle stars, worms, crabs, brachiopods and 

 echiuroids in certain areas and carnivorous crabs, snails, and fishes 



that come to prey on the residents. Eels, sharks, rays, perch, rock- 



15 

 fish, and occasional whales and sea lions also occur. Another 



important component of the biota of shallow coastal waters are those 



58 



