FISHERY BULLETIN: VOL. 83 NO. 3 



NOV 20 -DEC 2 1980 



Males 

 N=242 



Non-0 vigerous Females 

 Stage I 

 N=26 



rL 



Transitionals 

 N=22 



— 1 T" 



1 0- 

 5 • 



_^^ 



Non- ¥ige r o u s Females 

 Stage I 



N-53 F 

 r 1 ■=•  i 



1 

 5 • 



Ovtgerous Females 

 N-54 



Figure 3.-Pandalus montagui numerical lenp^th-frequency (iistribu- 

 tions by sex (including transitionals) anti repnxiuctive stage. 



10- 

 5 



30 

 20- 



10- 

 5  



Transitionals 

 N-' 23 



Transtttonais 

 N=23 



Non- ovigerous Females 

 Stage I 

 N = 204 



r4on - o vigerous Females 

 Stage II 

 N=27 



CARAPACE LENGTH (mm) 



females were obvious as a distinct size-group in the 

 November-December length-frequency data at 6-9 

 mm CL (Fig. 3B). At this time, these females made 

 up 15% of the newly recruiting age-group. The 

 relative abundance of age-group females was 

 considerably higher in the North Sea: 29-37% of 

 most samples in the Thames (Mistakidis 1957) and 

 about 50% in Northumberland (Allen 1963). On the 



sex In their first year following the repression of male sex 

 characteristics and never function as males are called secondary 

 females; and those which function first as males and then change 

 sex are called hermaphroditic females (Mistakidis 1957). Since no 

 distinction could be made in this study between the three types of 

 female P. mxmtagui, we have avoided the use of this termin()lc)gy 

 altogether and simply distinguish between individuals which re- 

 mained as males during their first year, those which were females 

 when they were first captured in November-December of their first 

 year, and those which apparently changed sex during their first 

 winter. 



other hand, only 11.2% of the age-1 P. montagui col- 

 lected in May 1965 in Grand-Rivifere were females 

 (Couture and Trudel 1969b). 



Size (Age) at Sex Transition 



Transitional P. montagui were collected during all 

 five sampling periods, but were most abundant in 

 late March (Table 6) following the end of the 

 breeding period. Sex transition apf)arently began in 

 Januar\', peaked in late March, and continued 

 through the summer and early fall, reaching a 

 minimum in late November. The rapid decline in the 

 relative abundance of males after January 1981 and 

 the accompanying increase in females after March 

 (Table 6) indicated that shrimp, which functioned as 

 males in the previous breeding season and became 



226 



