Age, growth and maturation of a rockfish species, Sebastes zonatus, in the Pacific coastal area off the Sanriku, northeastern Honshu, Japan

Abstract

Age, growth, and maturation of the coastal rock fish Sebastes zonatus were estimated on the basis of 1,485 specimens (78–359 mm in standard length: SL) collected in the Pacific coastal area off southern Iwate, northeastern Honshu, Japan by bottom long-line surveys from 2008 to 2018. The length (SL)–weight (BW) relationship was fitted by different allometry equations between both sexes. Transverse otolith sections indicated that an opaque zone was formed once a year, during May–October. The ages identified ranged from 1 to 9 years old, and a von Bertalanffy growth equation was calculated due to no significant difference between both sexes. Seasonal variations of the gonad somatic index indicated that matured females were occurred during March–May at age four or older. The features in age, growth and maturation of S. zonatus were equivalent to previous studies for the Sebastes vulpes species complex (S. zonatus and S. vulpes) along the Pacific coast off Iwate and off Aomori. The time-series for CPUE (inds./100 hooks) in each year class indicated that the relatively strong year classes were occurred in 2005, 2007, 2008, and 2015 from the present waters in the survey period.