Early epipelagic life-history characteristics of the North Pacific armorhead Pentaceros wheeleri

摘要

North Pacific armorhead Pentaceros wheeleri specimens collected through pelagic surveys in the North Pacific were analyzed to estimate the distribution, hatching season, growth, and the duration of the epipelagic life stage. Most pelagic specimens were collected in the central and eastern North Pacific (36–50°N, 178°E–137°W). This area was considered to be the nursery ground where larvae and juveniles inhabit until subsequent settlement to seamounts. The pelagic specimens were aged 0, 1, and 2?years, and their hatching periods were estimated to be from December to February based on the analysis of daily growth increments of otoliths. Standard length-at-age data were fitted to the mixed model of the von Bertalanffy growth curves, and growth coefficients L∞,k, and t0 were estimated to be 308 and 290?mm, 0.909 and 1.055, and 0.183 and 0.256?years for males and females, respectively. The standard length of fish at age 2.5?years was estimated at 263–271?mm, which is close to the size of demersal fish commonly harvested from the southern Emperor-northern Hawaiian Ridge seamounts. Since only a few age 3 fish were collected in pelagic samples, presumably most individuals shift to demersal life on seamounts before age 3.