To the issue of the origin of false annual rings on scale of juvenile Pacifi c salmon in the Bolshaya River system (Southeast Kamchatka)

Abstract

Seasonal growth and formation of annual rings on scale of juvenile Pacifi c salmon (Chinook, sockeye, coho and cherry salmons) restart in the Bolshaya River basin from mid May to mid June. In the last half of June and until the end of July, there are actually no additional formations on the scales of both underyearlings and yearlings. In August–October false annual rings (FARs) of dense circuli can be observed on scales of underyearlings of species mentioned above. Forming the extra FARs in the yearlings of coho and cherry salmon during their second season of growth not found (few exceptions only). The underyearling’s FARs are most frequent (17.4%) in Chinook salmon, following by sockeye salmon (12.1%) and coho salmon (7.1%), and the most rare (1.0%) in cherry salmon. The frequency of the FARs in yearlings during their growth period in the fi rst summer is 28.1% in Chinook salmon, 12.6% in sockeye salmon, 11.7% in coho salmon and 4.8% in cherry salmon.