Validity of Age Determination in the Fluvial Japanese Charr Salvelinus leucomaenis by Scale Reading

Abstract

The validity of age determination of the Japanese charr Salvelinus leucomaenis using scale readings was examined by the mark and recapture method in a Japanese mountain stream from 1986 to 1989. When recaptured within a year, all of the 3 (1 growth and 2 resting) scale zone fish were found to still have 3 zones on their scales. One year after marking, they had 4 (2 growth and 2 resting) or 5 (3 growth and 2 resting) zones on their scales and after 2 years, they still had 4 or 5 zones. Fish with 1 resting zone, i.e., 1 annulus, were regarded as age 1 + and fish with 2 annuli were regarded as age 2+. Consequently, age determination of the Japanese charr using scales might be reliable to 1+ age but doubtful for 2+ and older.