McFarlane and King: The validity of the fin-ray method of age determination for Ophiodon elongotus 
463 
0.8 r 
0.7 - 
E 
.E, 0.6 - o 
if) 
« 0.5 - 
D • 
| 0.4 - 
< 
0.3 - 
□ 
□ 
□ 
□ 
□ 
□ 
□ 
□ □ 
□0 
□ 
B 
□ 
0.2 ■ i i » i » < 
240 280 320 360 400 440 480 520 
Fork length (mm) 
Figure 4 
The mean diameter of the first (circles) and the second (squares) annuli are 
0.40 mm and 0.62 mm, respectively. The mean diameters do not show a change 
in value across the fork lengths observed. 
~G 
0 
if) 
13 
<5 
O 
E 
CC 
-O 
if) 
D 
c 
c 
nJ 
cn 
> 
<D 
CD 
< 
20 
16 
12 
8 
4 
3 
1 
1.-1 
5.-d 
1 .-3 
2. -8 4 
1 ip.-2o 3 
1 7.-49 11 1 
3. -75 21 1 
ip- '68 29 1 
4. -54 18 1 1 
,--f2 6 
1 
0 ~r — i 1 1 1 1 1 1 1 1 1 1 1 1 1 r 
0 4 8 12 16 20 
Age (avg. annulus diameter not used) 
Figure 5 
For all recovered lingcod, the ages determined when average annulus diam- 
eter measurements were used to estimate the location of the first and second 
annuli were approximately 1 year greater than ages determined when average 
annulus diameter measurements were not used (i.e. intercept on regression 
line=l). Because many data points overlapped, numbers indicate the number 
of observations at each point. 
this method in our validation study, we found that in most 
cases the number of annuli estimated after an OTC mark 
corresponded to the number of expected annuli based on 
years at liberty. 
Lingcod, and other species, resorb the central portion of 
their fin rays, making the identification of the first few an- 
nuli difficult in older fish (Beamish and Chilton, 1977). In 
order to obtain the most accurate ages, mean annular 
diameter measurements should be used routinely to locate 
the first and second annuli. We found no significant overlap 
between the first and second annular diameter measured 
in juvenile lingcod. It is therefore a useful criterion for 
