FISHERY BULLETIN: VOL. 75, NO. 2 

 TABLE 10. — Percentage of adult Pacific Ocean perch in each maturity stage, by stock, during 1968-73. 



1 All fish examined during this month came from research vessel catches. 



08- 



06- 



04 



2- 



MARCH 



FEMALES 



AUG -NOV 



08- 



06- 



04 



02- 



MALES 



MARCH 



molure 

 "maturing" 



30 35 40 45 25 30 



Length (cm) 



35 



40 



45 



FIGURE 18. — Seasonal changes in the relative gonad weight of 

 mature and "maturing" Pacific ocean perch by length group and 

 sex. 



"immature" males in all analysis of length or age 

 at maturity. 



There was considerable overlap in the relative 

 gonad weight of mature and "maturing" males 

 during March. Relative gonad weight of adult 

 males examined during the mating season in- 

 creased exponentially with size, however, so that 

 mature and immature fish were readily differen- 

 tiated for fish longer than about 32 cm. For smaller 

 fish, however, the relative size of the gonad was 

 not sufficient to determine whether or not a fish 

 was mature, and color had to be relied on to a large 

 degree. If the gonads were white rather than 

 brown, this was taken to indicate the presence of 

 developing sperm and the fish was classified as 

 mature. Whether or not these small males actu- 

 ally participate in mating remains an unanswered 

 question, however. 



Because mature and "maturing" males were 

 most readily differentiated when mature fish had 

 white, swollen gonads, only data collected during 

 June-October were used to determine size and age 

 at maturity. The data in Table 10 show that sig- 

 nificant quantities of males with Stage 3 gonads 

 were found during this period. 



386 



