Age estimation of striped marlin (Kajikia audax) in the eastern North Pacific using otolith microincrements and fin spine sections

Abstract

The age of striped marlin (Kajikia audax) in days and years (daily and yearly ages) were estimated by counts of otolith microincrements (n=25) and dorsal fin spine annuli (n=175) using specimens caught in the tropical eastern North Pacific between September and November 2004. Daily ages of small striped marlin (87.0–145.5cm lower jaw–fork length) were estimated to range from 81 to 239 days, which indicates that the species in the area grow, on average, to over 100cm within 4 months. Back-calculated hatch dates were estimated to be from March to July; this period is earlier than the known spawning season in a slightly more northern area. Approximately 20% of these year-0 striped marlin had one or more growth bands in the sectioned spine. They were thought to be false annual growth bands and excluded from yearly age estimation. The estimated yearly age of 175 individuals (87.0–228.4cm) ranged from 0 to 5 and was dominated by ages-0 to 3 (>90%). Age composition was different among three subregions in the eastern North Pacific.