5406 COHORT 



-"^ TOTAL FEMALES 



NON-GRAVID FEMALES 

 TOTAL MALES 

 -5309 COHORT 



SO 



10 





', ' 5506 sg 



10 12 14 16 IS 20 22 



FISHERY BULLETIN: VOL. 74. NO. 4 



ADULT MALE . FEMALE 

 Euphausia pacifica 



PATHWAYS OF GROWTH 



AND ABUNDANCE OF 



REPRESENTATIVE COHORTS 



200r 



5507 50 



10 12 14 16 18 20 22 



TOTAL LENGTH (mm) 



5512 COHORT 



10 12 14 16 18 20 22 



Figure 13. -Length-frequencies of adult males and females of Euphausia pacifica. Dashed lines trace development in males and 

 females. Frequencies of females without ripe eggs are indicated (pertinent to discussion of Sex Ratio). 



rapid during the larval phase and slower there- 

 after until large adulthood, 18-19 mm. Positive 

 perturbations appear at 6-7 mm, 9-10 mm, and 

 14-15 mm. Average survivorship is 16% during the 

 1 mo furcilia lan^a phase, as seen in the decline in 

 mean population density from 1,850 to 300/1,000 

 m-' (Figure 14) between 3 mm and about 6 mm in 

 body length which Boden (1950) has shown to be 



750 



larval phase. For juveniles, 6 mm through 9 mm, 

 survivorship is near 67%/mo over about 2 mo. 



For adolescents and young adults of 9-14 mm, 

 average survivorship remains nearly the same, 

 64%/ mo, then decreasing to 60% /mo through 18 

 mm. After that, population decline appears rapid, 

 possibly because sampling of such large in- 

 dividuals is not representative. Apparent 



