CALIFORNIA FISH AND GAME. 171 



NOTE ON THE HABITS AND USE OF THE SMALL SAND CRAB 



(Emerita analoga)/'= 



By FRANK W. WEYMOUTH, Stanford University. 



Of the many baits used for surf and pier fisliiug iu southern 

 California, few are more popular than the "soft-shelled" sand crab, 

 of which numbers may be seen for sale in the fish markets on the piers 

 at Santa Monica, Venice, Long Beach, Corouado and other coast 

 towns. Some recent observations on its habits suggested that those 

 who use it as bait might be interested in its mode of life and where 

 it may be caught. 



The small sand crab, as it may be called to distinguish it from a 

 larger form also found in the sand, or more technically Emerita 

 analoga, is found on sandy beaches exposed to the open ocean along 

 the entire coast of California, but never in bays or other sheltered 

 locations. The reason for this will be clear when we have considered 

 its feeding habits. At the level washed by the waves it burrows in 

 the sand, and is found grouped in beds which can be recognized even 

 at a distance by peculiar diamond-shaped ripple marks in the water 

 running off the sand after the breaking of the wave. These ripples 

 are caused by the feathered "feelers," or antennae, of the sand crab, 

 which it thrusts up into the receding wave. With these it combs from 

 the water the microscopic animals and plants upon which it feeds. 



If one has patience to wade into such a bed and wait quietly until 

 the crabs have recovered from their first alarm, the interesting process 

 of feeding may easily be watched. As the water clears of sand after 

 the inrush of the wave, dozens of pairs of the plume-like antenna will 

 be seen to pop out of the sand into the seaward-running water, where 

 they remain until the wave drains oft', occasionally disappearing for a 

 fraction of a second to be freed of their catch of tiny organisms. 

 Corresponding to this habit of feeding on material too fine to be 

 chewed, the jaws, which have hard-cutting edges in other crabs, are 

 here small, soft, degenerate vestiges. 



If a shovel is thrust into the sand of one of these "beds" it will 

 turn out scores of these crabs which "dig in" again so rapidly that 

 few can be caught. If numbers are wanted the best way to catch 

 them is to shovel the sand, crabs and all, into a box having wire screen 

 in the sides, and let the sand be washed out by the waves as they 

 sweep in and out. Another but less efficient method sometimes prac- 

 ticed is to hold a screen across one of the sand gullies found in this 

 part of the beach and so catch the crabs which happen to be swimming 

 a1)out in the receding wave. 



Observations recently made show that the crabs move up and down 

 the beach with the tides so that the beds may always be found in the 

 area washed by the waves, and here they may easily be recognized bj'" 

 the ripple marks already mentioned. 



Crabs caught by any of these methods will be noticed to differ 

 much in size. In this species, unlike most of the Crustacea, the males 

 are much smaller than the females, and it will l)e found during the 

 breeding season, which falls in the summer months, that only the 



♦California State Fisheries Laboratory, Contribution No. 8. 



