134 
Fishery Bulletin 95( 1 ), 1997 
38 
36 
34 
32 
30 
28 
26 
24 
1 2 3 4 5 6 7 
38 
36 
34 
32 
30 
28 
26 
24 
1 2 3 4 5 6 7 
No. of rings 
Figure 6 
Length at age and 95% Cl of the (A) 1980 spring-hatched and (B) 1979 
autumn-hatched cohorts in the late fall (October-December), once the 
spawning season had been established as determined by their matu- 
rity stages for each cohort ( age is expressed as the number of otolith 
rings — see text). 
t i r 
S 
o 
■S 
W) 
c 
1 ) 
hJ 
studies have concluded that either density-dependent 
(Anthony, 1971; Lett and Kohler, 1976) or density- 
independent factors (Moores and Winter, 1982), or 
both (Anthony and Fogarty, 1985; Haist and Stocker, 
1985), contribute to the significant inter- and intra- 
annual variations in the growth rates of juvenile 
herring. There has developed a general consensus 
among these authors that differences observed in 
length at age between year classes of adult herring 
originated in the juvenile phase, before maturation. 
Further, Toresen (1990) compared the growth of ju- 
venile Norwegian herring from the 1950’s with that 
from the 1970’s and concluded that variable growth 
rates depended mainly on where the juveniles spent 
their early years. Large cohorts showed both den- 
sity-dependent growth when these cohorts were dis- 
tributed in the fjords, as well as environmentally 
induced growth variations when components of the 
cohort were distributed in less productive areas of 
the Barents Sea. This study demonstrated that dif- 
ferent components of a single cohort can encounter 
different growth conditions before maturation and 
thus can experience different growth rates. 
Density-dependent and environmentally induced 
variability in growth and condition in the juvenile 
phase is believed to affect the onset of first matura- 
