Age-based life history of Pacific longnose parrotfish Hipposcarus longiceps from New Caledonia.

Abstract

The Pacific longnose parrotfish, Hipposcarus longiceps, is a medium‐ to large‐bodied scarine labrid that is among the most commonly harvested species in mixed reef fisheries across the Indo‐Pacific. Despite its ecological and fisheries importance, assessments of stock status and development of appropriate management strategies for the species have been limited by an absence of biological information. To date, the only detailed studies of the biology of H. longiceps have occurred in tropical regions. This study examined the biology of H. longiceps in southern New Caledonia, towards the southernmost extent of the species' distribution. In addition, resulting estimates of longevity and asymptotic length were compared against those derived for the species elsewhere in the Pacific, and regional patterns in these parameters were explored for correlation with sea surface temperature (SST). A total of 212 H. longiceps were collected from commercial fishers or fish markets between September 2015 and March 2017. Sampled individuals ranged from 28.2 cm fork length (L F) to 57.3 cm L F, and from 424 g to 3773 g. Examination of sectioned otoliths showed a clear pattern in increment formation, with opaque zones forming annually in most individuals between July and August (i.e., austral winter). Estimated longevities were similar between sexes, at ~18 years for females and ~19 years for males. These estimates extend the reported longevity of H. longiceps by at least 5 years. Despite this species being a diandric protogynous hermaphrodite, sex ratios were only slightly female biased, with 1 female:0.6 males. Primary males (i.e., those individuals that are male at first sexual maturity) constituted 30% of all sampled individuals and 79% of all males. A clearly defined, yet protracted, spawning season was evident, with peak spawning occurring from December–February, extending from November to April in some individuals. The estimated median length (L 50) and age (A 50) at female maturity were 38.9 cm L F and 5.7 years, respectively, while the estimated length at which females changed sex to secondary males was 52.5 cm L F. Reported longevity and asymptotic length were found to exhibit considerable regional variation, and both were negatively associated with SST. The results highlight the importance of geographically disparate studies into the species' biology, inform future assessments for the species, provide key baseline information for comparative work and improve understanding of spatial patterns of the life history of parrotfish species.