McQuinn: Year-class twinning in sympatric spawning populations of Clupea harengus 
131 
25 
15 20 25 30 35 
25 
15 20 25 30 35 
Length (cm) 
Figure 3 
Length-frequency distributions of the (A) 1980 spring-hatched, 
(B) 1982 spring-hatched, and (C) 1986 autumn-hatched cohorts 
as immature 3-year-olds in 1983, 1985, and 1989, respectively. 
Table 2 
Mean lengths and standard deviations of immature western Newfoundland herring from the 1980 and 1982 spring-hatched 
cohorts as 2- and 3-year-olds in the spring (April-June) and the fall (October-December) fisheries. 
1980 spring-hatched cohort 
1982 spring-hatched cohort 
Year 
Age 
Fishery 
Mean length 
(cm) 
SD 
n 
Year 
Age 
Fishery 
Mean length 
(mm) 
SD 
n 
1982 
2 
Spring 
— 
— 
— 
1984 
2 
Spring 
187.96 
12.87 
ii 
Fall 
248.91 
27.23 
35 
Fall 
248.47 
15.17 
75 
1983 
3 
Spring 
247.86 
20.87 
72 
1985 
3 
Spring 
252.11 
14.50 
77 
Fall 
278.80 
17.43 
585 
Fall 
283.27 
10.56 
310 
