462 
Fishery Bulletin 99(3) 
Table t 
The number of estimated annuli after the OTC mark 
versus the expected annuli based on years at large. Num- 
bers in bold indicate those samples in which the number of 
observed annuli equaled the number of expected annuli. 
Expected annuli 
Estimated annuli 12 3 4 
0 
1 
2 
3 
4 
3 1 — — 
328 3 — — 
16 60 
1 1 39 1 
4 3 
(Fig. 20 and clearly visible with ultraviolet light (Fig. 
2D). This fin ray had three annual growth zones after the 
OTC mark, each comprising opaque and translucent zones 
(Fig. 20. An annual growth zone can contain several dis- 
tinct translucent zones, i.e. checks. In this example, the 
tenth labelled annulus did not appear to be continuous 
and could, therefore, be interpreted as a check (Fig. 1, E 
and F). Although this area likely contained checks, the 
thickness and prominence of the labelled translucent zone 
around most of the fin-ray section (Fig. 20 indicated that 
it was the edge of the tenth annulus. 
Fish numbered B8224635 was recovered in July 1985 
and was estimated to be 9 years old (Fig. 3). Unlike the 
previous two examples, the first two annuli were difficult 
to determine because of resorption in the central portion 
of the fin ray (Fig. 3). We used the diameter measurement 
criteria of Chilton and Beamish (1982) to locate the first 
and second annuli. 
The 46 juvenile lingcod available from the creel survey 
in 1987 were used for first and second annular measure- 
ments. The mean first annular diameter was 0.40 mm 
(SD=0.07) and the mean second annular diameter was 
0.63 mm (SD=0.11). With one exception, there was no 
overlap between the measured diameter for the first an- 
nulus and those measured for the second annulus and 
the two means were significantly different (Ctest, t= 17.46, 
df=86, P<0.0001). The mean annular diameter did not 
vary across the range of fork lengths observed (Fig. 4). 
Ages determined by using average diameter for the lo- 
cation of first and second annuli measured in the late- 
1980s were generally one year older than ages determined 
without using a measurement to locate the first two an- 
nuli (Fig. 5). There appeared to be no trend related to 
age. However, across all ages, the unmeasured estimates 
ranged from three years younger to three years older than 
estimates made with the measurement criteria (Fig. 5). 
This result is likely due to the exclusion of annuli that 
cannot be recognized or due to the inclusion of checks, mis- 
taken as annuli, in some fish. There was no difference in 
the number of annuli estimated after the OTC mark. The 
one-year aging bias is illustrated in the age composition 
Figure 3 
Fish numbered B8224635 had resorbed (R) cen- 
tral portion of the fin ray, making identification 
of the first two annuli (arrows) difficult. Subse- 
quent annuli are indicated by dots. Total age 
was 9+. 
for the lingcod recovered in 1983 (n=341). The age com- 
position for the ages determined with the measurement 
criteria had a mode of 6 years, whereas the age composi- 
tion for ages determined without the measurement crite- 
ria had a mode of 5 years (Fig. 6). For all of the samples, 
the estimated ages ranged from three to 18 years. 
Discussion 
Accurate age determination is essential for proper stock 
assessment and fisheries management. Although aging 
inaccuracies of one year might not be critical in long-lived 
species (e.g. 80-year-old rockfish), they can have serious 
stock assessment implications for shorter-lived species, 
such as lingcod. This is likely true because shorter-lived 
species typically have only four or five year classes that 
dominant the fishery. It is therefore important to develop 
accurate methods for age determination and to validate 
those methods. The fin-ray method first described by 
Beamish and Chilton (1977) is an accurate method for age 
determination of lingcod. Annular growth is represented 
by an opaque (summer growth) and a translucent (winter 
growth) zone and the edge of the annulus is assigned to 
the translucent zone (Beamish and Chilton, 1977). Using 
