The fin-ray method of aging lake whitefish

We report the results of a long-term age validation of the fin-ray method of aging lake whitefish (Coregonus clupeaformis). We further compare fin-ray ages with otolith ages and describe a technique to back-calculate lengths of lake whitefish. Using ages determined from individuals when tagged, we correctly predicted the ages determined from fish when they were recaptured one to 28 years later for 1092 (73%) of the 1492 individuals that we examined. When differences occurred between predicted and actual ages at recapture, there was no tendency for the actual ages to be greater or less than the predicted age. We found no significant difference between fin-ray and otolith ages for individual lake whitefish from two other lakes, although the ages agreed for only 49% of the age pairs. We used the upper section of the first pelvic fin ray to back-calculate fork lengths of lake whitefish from one population using the direct proportionality method, and compared these predicted lengths with actual lengths recorded one to three years earlier when fish were tagged to validate the method.