Moss Landing were also of interest. If these populations are the major 

 source of gametes, keeping them at the present level could prove essential 

 in providing recruitment for the heavily clammed intertidal area. 



2. Methods and Materials . 



About 17 to 20 clams were collected each month from four locations to 

 determine the degree of gonadal maturity. Clams were collected in the 

 intertidal zones near the north end of Manresa Beach from November 1971 

 to October 1973, and Moss Landing from February 1972 to October 1973, 

 and the subtidal zones at Moss Landing from February 1972 to September 

 1973, and Pismo Beach from June to October 1973. The clams were then 

 taken to the laboratory and either processed immediately or put into 

 running seawater and processed within 48 hours. In processing, the clam 

 was removed from the shell and preserved in Formalin. A small block of 

 tissue that included the gonad was later cut from the base of the foot, 

 washed overnight in water, dehydrated with alcohol, saturated with 

 paraffin, and poured into a mold. The mold was sliced into sections, 

 7 micrometers thick, which were stained with eosin and haemotoxlyn and 

 mounted on slides. The tissues were then examined and separated by 

 the stage of gonadal maturity, using a classification modified by Ropes 

 and Stickney (1965). The classification called the gonad inaative if 

 the follicle was collapsed with no gametes (Fig. 5), early active if 

 small oocytes had begun forming on the follicle walls (Fig. 6), late 

 active if oocytes were rounded with well-developed nuclei and attached 

 to the follicle walls (Fig. 7), matwce or vi-pe if most oocytes were 

 well developed and lying free within the follicle (Fig. 8), partly spent 

 if the follicle was partially empty of mature oocytes (Fig. 9) , and 

 spent if the follicle was empty with the exception of residual oocytes 

 (Fig. 10) . Male gonads were not classified because of the extreme 

 difficulty in recognizing the various maturation stages of the testes 

 packed with deeply staining spermatozoa that obscured all detail. 



3. Results . 



a. Stages of Gonad Maturity . Examination of the histological prepa- 

 rations of gonad tissue showed that female Pismo clams in Monterey Bay 

 were in the early active stage from December to July (dominant from 

 January to March, Table 6 and Fig. 11) and the late active stage from 

 March to June (dominant in April and May, Fig. 12) . The clams attained 

 each stage about 1 month earlier in 1973 than 1972. Intertidal clams at 

 Manresa Beach reached each stage 1 month earlier than intertidal clams at 

 Moss Landing. Subtidal clams at Moss Landing remained in each stage 1 

 month later. 



The ripe stage of the clams was from May to September (Fig. 13) . 

 Intertidal clams reached this state at Moss Landing 1 month later in 1973 

 than in 1972, and at Manresa in May of both years. Subtidal clams at 

 Moss Landing reached this stage 1 month later than intertidal clams from 

 Moss Landing or Manresa Beach. Intertidal clams at Manresa and subtidal 



27 



