Number of Circuli and Time of Annulus Formation on Scales of Pink Salmon (Oncorhynchus gorbuscha)

Abstract

Mean numbers of circuli on scales of juvenile pink salmon collected along the coast of North America in 1964 increased from 1.7 on June 23 to 17.4 on September 10. On scales of adults collected from the eastern North Pacific Ocean from 1962 to 1965, mean numbers of circuli ranged from 24.1 on January 23 (1964) to 46.9 on September 2 (1962). The fork length at time of scale formation was approximately 60 mm. Mean fork length increased with the total number of circuli. The relationship of fork length to number of scale circuli showed some variation between stocks. The winter ring was present or was being formed on the majority of scales taken in late January. The development of the annulus varied considerably among individual fish.