464 
Fishery Bulletin 99(3) 
120 
80 
40 
20 
. 
p 1 
Hi 
ill 
f 
2 3 4 5 6 
10 11 12 13 14 15 16 17 18 19 
Age (yr) 
Figure 6 
Age composition for the 341 lingcod recovered in 1983 when no measurements 
were used to estimate location of first and second annuli (striped bars) and 
when average measurements were used to estimate their location (solid bars). 
age determination and can be used for 
lingcod inhabiting waters off the coast 
of British Columbia. The fin-ray method 
for age determination is routinely ap- 
plied to other species (Beamish, 1981) 
and we suggest investigators examine 
similar criteria to ensure the identifica- 
tion of the first few annuli. 
Consistent use of mean annular diam- 
eter for age determination of lingcod will 
enable the best estimation of ages. We 
have illustrated that when the estab- 
lished criteria are not applied to identify 
the first few annuli, systematic underag- 
ing of approximately one year occurs — 
a serious consequence for stock assess- 
ment. For example, underestimates of 
age would overestimate mortality rates. 
If managers set fishing mortality equal 
to natural mortality (i.e. F-M) to es- 
timate fishery yields, then overfishing 
would result (Tyler et al., 1989). If re- 
cruitment were estimated from a catch- 
at-age analysis, erroneous age compo- 
sition and overestimates of mortality 
would lead to gross overestimates of recruitment (Tyler et 
al., 1989). 
Recently, rapid and major shifts in marine ecosystems 
have been shown to have consequences for the biology 
and behavior of a large number of fish species (Beamish 
et al., 2000). These shifts can occur within a year; there- 
fore it might be expected that growth of some species 
could change rapidly because of environmental effects. Ex- 
amination of growth time series would likely indicate a 
change coincident with environmental changes. However, 
we have illustrated that a rapid change in a growth time 
series can also be the result of the change in aging criteria. 
Therefore, for age determination to be valid and effective 
in fishery and ecosystem research, the criteria used should 
be routinely reviewed and verified. 
Literature cited 
Beamish, R. J. 
1981. Use of fin-ray sections to age walleye pollock, Pacific 
cod, and albacore, and the importance of this method. 
Trans. Am. Fish. Soc. 110:287-299. 
Beamish, R. J., and D. E. Chilton. 
1977. Age determinations of lingcod ( Ophiodon elongatus ) 
using dorsal fin-rays and scales. J. Fish. Res. Board Can. 
34:1305-1313. 
Beamish, R. J., and G. A. McFarlane. 
1983. The forgotten requirement for age validation in fish- 
eries biology. Trans. Am. Fish. Soc. 1 12: 735-743. 
Beamish, R. J, G. A. McFarlane, and J. R. King. 
2000. Fisheries climatology: understanding decadal scale 
processes that naturally regulate British Columbia fish 
populations. In Fisheries oceanography: an integrative 
approach to fisheries ecology and management (P. J. Har- 
rison, and T. R. Parsons, eds.), p. 94-139. Blackwell Sci- 
ence Ltd., Oxford. 
Cass, A. J., and R. J. Beamish. 
1983. First evidence of validity of the fin-ray method of age 
determination for marine fishes. N. Am. J. Fish. Man. 
3:182-188. 
Cass, A. J., E. Cameron, and I. Barber. 
1982. Lingcod tagging study off southwest Vancouver Island, 
M.V. Pacific Eagle — July 14-27, 1982. Can. Data Rep. 
Fish. Aquat. Sci. 406, 84 p. 
Chilton, D. E., and R. J. Beamish. 
1982. Age determination methods for fishes studied by the 
Groundfish Program at the Pacific Biological Station . Can. 
Spec. Pub. Fish. Aquat. Sci. 60, 102 p. 
McFarlane, G. A., and R. J. Beamish. 
1987. Selection of dosages of OTC for age validation stud- 
ies. Can. J. Fish. Aquat. Sci. 44:905-909. 
Rien, T. A., and R. C. Breamesderfer. 
1994. Accuracy and precision of white sturgeon age esti- 
mates from pectoral fin-rays. Trans. Am. Fish. Soc. 123: 
255-265. 
Rossiter, A., D. L. G. Noakes, and F. W. H. Beamish. 
1995. Validation of age estimation for lake sturgeon. Trans. 
Am. Fish. Soc. 124:777-781. 
Stevenson, J. T., and D. H. Secor. 
2000. Age determination and growth of Hudson River Atlantic 
sturgeon, Acipenser oxyrinchus. Fish. Bull. 97:153-166. 
Tyler, A. V., R. J. Beamish, and G. A. McFarlane. 
1989. Implications of age determination errors to yield esti- 
mates. In Effects of ocean variability on recruitment and 
an evaluation of parameters used in stock assessment 
models (R. J. Beamish, and G. A. McFarlane, eds.), p. 27- 
35. Can. Spec. Publ. Fish. Aquat. Sci. 108. 
