KOSKNBLUM and NIESEN: SPAWNING CYCLE OK A/1 .4 4/ffiN/lftM 



CANDLESTICK 



ISABEL 



X = 57.0 

 SD = 9.1 

 n = 447 



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FOSTER CITY 



X = 61.6 

 SD = 13.3 

 n = 351 



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BURLINGAME 



X = 55.0 

 SD = 12.3 

 n =466 



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SIZE CLASS 



Figure 2. -Size-frequency histograms for the four populations studied. Size classes are (in mm) 10.0-14.9, 



15.0-19.9, etc. 



sampled were inactive and 5% still showed a few 

 mature gametes which would probably have been 

 resorbed. All individuals were inactive by the end of 

 December 1979. 



The first sign of gonadal activity appeared at the 

 end of January 1980; by March, 82.1% of the clams 

 sampled were active. In April, all individuals were 

 either ripe or spawning. Peak spawning occurred 



407 



