u 



a: 



1973-1974 



MONTHS 



FISHERY BULLETIN: VOL. 76, NO. 1 



RESULTS 



Reproductive Cycle 



Reproductively active individuals were encoun- 

 tered throughout the 3-yr study period, the largest 

 numbers occurred in April and July of 1973, 

 March and early July of 1974, and mid-March of 

 1975 (Figure 3). Due to the limited sampling 

 undertaken during the summer of 1975, the sum- 

 mer spawning peak cannot be determined with 

 certainty. 



In February 1974, gametogenesis had begun in 

 both sexes (Figure 4). Ripe and partially spawned 

 clams were observed in mid-March. By late April, 



Figure 3. — Proportions o^Mya arenaria population with active 

 or inactive gonads during 1973-74, 1974-75, and 1975-76. 

 Cross-hatched portions of each bar represent inactive gonads 

 (indifferent, no gamteogenesis, or spent); solid portions repre- 

 sent active gonads (developing, ripe gametes, or partially spent). 

 Observations on males and females were combined. 



CI] SPAWNING 



nSPENT 







FIGURE 4 



158 



F  M ' A  m' J ' J ' A SO N D I J F M A M J J ' A ' S ' ' N ' D I J 

 —Proportions of male and female Mya arenaria with gonads in each developmental phase during 1973-74 and 1974-75. 



