The validity of the fin-ray method of age determination for lingcod

Oxytetracycline (OTC) injections were used in a mark-recapture experiment undertaken to validate the fin-ray method of age determination of lingcod (Ophiodon elongatus). In most cases, the number of annuli that formed beyond the OTC mark corresponded to the number of years at liberty. Expected and interpreted annuli counts from fin rays matched in 94%, 92%, 91%, and 75% of lingcod at liberty 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 establishing and following age determination criteria is illustrated by the change in age composition due to misidentification 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 underestimated mortality rates if fishery managers 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.