BROUSSEAU: REPRODUCTION OF MYTILUS EDULIS 



most mussels were in a ripe condition (stage III) (Fig. 

 3). As spawning proceeded, the variance increased, 

 indicating that the mussels did not all release 

 gametes at the same time. A second peak in the 

 variance, however, occurred during February and 

 March 1981 and December and January 1982. This 

 apparent synchrony was probably due to an extend- 





ed spawning period, especially during 1982. During 

 that period, mussels were reported in various repro- 

 ductive states (gametogenic, gravid, and spawning). 



Photomicrographs of representative male and 

 female stages in the spring and summer peaks of the 

 annual cycle are shown in Figure 5. Stages are 

 assigned according to the "index of bivalve gonad 



December 1981, h) late-developing female (stage II), 17 March 1981, i) ripe female (stage III), 4 May 1982, j) spawning female, 5 October 

 1981, k) recently spent female, 22 June 1982, 1) hermaphrodite, 22 January 1982. 



737 



