populations are large and the major source of gametes supplying recruit- 

 ment to the heavily clammed intertidal areas. Fitch (1965) provided the 

 only evidence of the beds, reporting large numbers of clams at one 

 subtidal location in southern California. 



This study determines the intertidal and subtidal areas of presence 

 and absence of Pismo clams in Monterey Bay and, for those areas where 

 the clams were present, estimates density, dispersion pattern, and 

 vertical distribution. A comparison was also made of physical charac- 

 teristics of beaches with and without clams. 



2. Methods and Materials . 



Intertidal samplings were taken at 10 randomly selected locations 

 in Monterey Bay (Fig. 1). Sampling at eight locations began during 

 June, July, and August 1972. A sample was taken at the Salinas River 

 mouth in November 1972, and at Fort Ord in December 1972. Rio del Mar, 

 Monterey Bay Academy, Sunset State Beach, Zmudowski State Beach, and 

 Moss Landing were resampled during June and July 1973. Twenty 1 -square- 

 meter samples from each station were randomly selected within a 18- by 

 24-meter grid placed so the lowest edge was at approximately the -1.0-foot 

 tidal level. Each square meter was raked with a small hand rake with 

 tines that penetrated 6 inches. A 0.25-square-meter area was subsampled 

 by taking 13 cores (0.018 square meter) that penetrated 6 inches into 

 the sand. The contents were emptied into a sieve box and sieved in the 

 surf (Oliver and Slattery, 1973) . The rake provided an adequate sample 

 of clams greater than 39 millimeters in length since these clams could 

 not pass between the tines. The core samples were quantitative for 

 clams from 10 to 39 millimeters long. The lower limit was dictated by 

 the mesh size of the sieve box. Each clam was measured, the quadrat 

 of occurrence noted, and then reburied. Five sediment cores were also 

 taken at each of the distribution study sites. 



Subtidal samplings were taken offshore of each intertidal sampling 

 station at the -15-foot tidal level in July, August, and September 1972, 

 except for the Fort Ord station which was not sampled due to heavy surf. 

 Because of wave action, the -15-foot tidal level was the shallowest 

 depth the samples could be obtained from a boat. No subtidal sampling 

 was done in 1973 because of the low number of clams found in 1972. 

 The sampling device was a modified portable gold dredge (Brett, 1964), 

 which has also been used in surveys for macrofauna (Hughes and Thomas, 

 1971) and has been compared with other benthic samplers (Hodgson, 1973, 

 unpublished). The gold dredge is powered by a 7-horsepower portable 

 gasoline engine which pumps high-pressure water to the diver below. 

 Water enters the middle of an L-shaped tube 6 inches in diameter and 

 discharges at one end of the tube, causing a powerful suction at the 

 other end which lifts sediment and clams. A bag of 3-millimeter nylon 

 mesh is attached to the discharge end to catch the clams, and sediment 

 is expelled through the mesh leaving the clams and larger particles. 

 Twenty 1-square-meter samples to a depth of 6 inches were taken at each 



