Age determination and growth estimation from otolith micro-increments and fin spine sections of blue marlin (Makaira nigricans) in the western North Pacific.

Age determination and growth estimation of blue marlin (Makaira nigricans) were performed by combining method of otolith micro-increment counts of 27 young (17-185-cm lower jaw-fork length, LJFL) and sectioned dorsal fin spines of 571 adult individuals (155-352 cm). Otolith micro-increments were counted with ages of 26-338 days old. The estimated mean length (185 cm) at Year 1 and growth rate were used to predict the position of the first annual growth band in sectioned fin spines. Distinct growth bands were formed in fin spines annually between September and October. Indistinct growth bands were considered false-annual growth bands. The observed and back-calculated LJFLs at each age were highly variable for both sexes. Von Bertalanffy growth parameters were estimated using mean back-calculated LJFL data as: L_∞ = 295 cm, k = 0.23, t₀ = -3.31 years for females and 212 cm, 0.29, -4.49 years for males. Females grew to >200 cm in 2 years and to >250 cm in 5 years on average, whereas the growth of males slowed appreciably after they reached the age of 1 year. This is the first study of blue marlin growth for entire life stages. Although age and growth of blue marlin (Makaira nigricans) have been studied for decades, no results are generally accepted to date. The present study described the growth of blue marlin from juvenile to adult stages using otolith micro-increment and sectioned fin spine analyses first time. Obtained results will largely improve the stock assessment of the species. [ABSTRACT FROM AUTHOR]