459 
Abstract— Oxytetracycline (OTC) in- 
jections were used in a mark-recap- 
ture experiment undertaken to validate 
the fin-ray method of age determina- 
tion of lingcod ( Ophiodon elongatus). In 
most cases, the number of annuli that 
formed beyond the OTC mark corre- 
sponded to the number of years at lib- 
erty. Expected and interpreted annuli 
counts from fin rays matched in 94%, 
92%, 91%, and 75% of lingcod at lib- 
erty for one, two, three, and four years, 
respectively. These results validate the 
annual pattern of banding in fin-ray 
sections of fish up to 18 years of age. 
One of the consequences of not estab- 
lishing and following age determina- 
tion criteria is illustrated by the change 
in age composition due to misidentifi- 
cation of the first few annuli. A change 
in age composition has implications for 
stock estimates, such as mortality rates, 
and harvest strategies. For example, 
overfishing could result from underes- 
timated mortality rates if fishery man- 
agers used a strategy that set fishing 
mortality equal to natural mortality. It 
is recommended that age determination 
criteria be routinely assessed to provide 
reliable age estimates. 
Manuscript accepted 18 December 2000. 
Fish. Bull. 99:459-464 (2001). 
The validity of the fin-ray method of age 
determination for lingcod ( Ophiodon elongatus ) 
Gordon A. McFarlane 
Jacquelynne R. King 
Pacific Biological Station 
Fisheries and Oceans Canada 
Nanaimo, British Columbia 
V9R 5K6 Canada 
E-mail address (for G. A. McFarlane): mcfarlanes@pac.dfo-mpo.gcca 
Lingcod ( Ophiodon elongatus) are dis- 
tributed off the west coast of North 
America in the nearshore waters from 
Baja, California, to the Shumigan 
Islands, Alaska. They have been an 
important component of the commer- 
cial fishery off British Columbia since 
the mid- 1880s and a favorite target of 
recreational anglers since the 1950s. 
They inhabit nearshore waters and are 
commonly found along the bottom at 
depths ranging from 3 to 400 m; how- 
ever most are found in rocky areas 10 
to 100 m. Growth during the first years 
of life is rapid and up to age 2 it is 
similar for males and females, both 
reaching an average length of 45 cm. 
After age 2, females grow faster than 
males and the growth of males tapers 
off at about age 8, whereas females con- 
tinue to grow rapidly until about age 
12-14. For waters off the west coast of 
Canada, the maximum age recorded for 
lingcod has been 14 years for males and 
20 years for females. Females reach 
lengths in excess of 100 cm, whereas 
males rarely exceed lengths of 90 cm. 
The fin-ray method for age deter- 
mination has been used for a wide 
range of freshwater and marine species 
such as sturgeon ( Acipensei ■ spp.), Pacif- 
ic salmon (Oncorhynchus spp.), brown 
trout ( Salmo trutta), whiter sucker (Ca- 
tostomus eommersoni), lake whitefish 
( Coregonus clupeaformis), channel cat- 
fish ( Ictalurus punctatus ), common carp 
( Cyprinus carpio), ide ( Leuciscus idus), 
tuna (Thun nus spp.), rudd ( Scardinius 
erythropthalmus), chub ( Squalls ceph- 
alus), roach ( Rutilus rutilus), bream 
( Abramis brama), and yellow perch ( Per- 
ea fluviatilus ) (Beamish 1981). Howev- 
er, in only a few instances have there 
been attempts in recent years to val- 
idate age estimates with the fin-ray 
method ( Rien and Breamesderfer, 1994; 
Rossiter et al., 1995; Stevenson and 
Secour, 2000) despite the caution posed 
by Beamish and McFarlane ( 1983) that 
validation of age determination tech- 
niques is difficult, albeit critical. 
Beamish and Chilton (1977) devel- 
oped a method of aging lingcod that 
used thin sections of fin rays com- 
bined with mean annular diameter 
measurements to locate the position 
of the first and second annuli. This 
technique allowed estimates of mortal- 
ity rates, growth rates, and fecundity 
to be determined for each age group. 
These rates strongly influenced assess- 
ment and management approaches for 
lingcod. Preliminary validation of the 
method was accomplished by using a 
mark-recapture experiment in conjunc- 
tion with injections of oxytetracycline 
(OTC) (Cass and Beamish, 1983). How- 
ever, this preliminary validation of the 
method was based on only four recov- 
eries. A second experiment was initiat- 
ed in 1982 to complete the validation of 
the fin-ray method for lingcod. Our re- 
port presents the results of this second 
mark-recapture study combined with 
OTC injections. 
During the course of analyzing ling- 
cod age data in the early 1990s, it be- 
came apparent that the annular diam- 
eter measurement criteria suggested by 
Beamish and Chilton ( 1977) were no lon- 
ger being followed. Resulting parameter 
estimates based on these age estimates 
had changed. This resulted in a mis- 
understanding of growth, mortality, and 
age at maturity, which had implications 
for development of management strate- 
gies for lingcod. We therefore also report 
on a re-examination of the measurement 
