BUTLER: NORTHERN ANCHOVY GROWTH IN THE CALIFORNIA CURRENT 



than those of 1983 (Figs. 3, 4). Cohorts did not 

 differ significantly in growth until approximately 

 40 mm. The age of the end of the late larval (10 

 mm) period was 20 days in 1980 and 19 days in 

 1983. A local minimum for gi'owth rates of 1983 

 fish occuiTed at about 35 mm and at about 42 mm 

 for gi'owth rates of 1980 fish. This corresponds, 

 appro.ximately, to metamorphosis from late lar- 

 val stage to juvenile stage. The duration of the 

 late larval period (10-35 mm) was about 70 days 

 in both 1980 and 1983. 



After metamorphosis, growth rates increased 

 in 1980 and 1983 until about 40 mm. At about 40 

 mm, the gi'owth rates of the two cohorts di- 

 verged, and the mean back-calculated growth 

 rate of the 1983 cohort was well below the esti- 

 mated 95% confidence interval of the 1980 

 cohort. Growth rates declined steadily in 1983 at 

 sizes larger than 40 mm, while growth rates of 

 about 0.4 mm/d were sustained in 1980 until al- 

 most 60 mm. After 60 mm, growth dechned at 

 about the same rate as the decline in the 1983 



5 20 



60 80 100 120 140 160 180 200 



AGE (days) 



Figure 3. — Length versus age of northern anchovy larvae and juveniles of the 

 March 1980 and 1983 cohorts back calculated from daily increments in otoliths. 



>, 

 ra 

 ■o 

 \ 

 E 

 E 



X 



o 

 o 



0.7 



0.6 



0.5 



0.3 



1980 



40 50 60 



LENGTH (mm) 



70 



80 



Figure 4. — Age-specific growth rates back calculated from daily increment 

 widths of northern anchovy spawned in March 1980 and March 1983. Growth 

 rate of length in mm per day. Shaded areas are 95% confidence intervals. 



649 



