Age estimation of barracouta (Thyrsites atun) off southern New Zealand

Abstract

Age determination of barracouta (Thyrsites atun) by counting translucent zones in whole otoliths was validated by examining the number of zones in otoliths from consecutive juvenile modes and following the progression of a strong year class in age-frequency distributions. Readings from whole otoliths, rather than otolith sections, do not result in under-ageing of this species. The ageing interpretation was supported by the progression of a length mode in commercial catch samples over 5 years. The available data indicated a wide variation in year class strengths between years, a characteristic that was very useful in the validation study. Von Bertalanffy growth parameters were calculated, separately by sex, for barracouta from the Southland shelf, New Zealand. Female barracouta reach a significantly larger size than males.