Life history traits of the Pacific longnose parrotfish Hipposcarus longiceps (Labridae, tribe: Scarinae) in subtropical waters

Abstract

The Pacific longnose parrotfish, Hipposcarus longiceps, is an important target species in tropical and subtropical waters of the Indo-Pacific. However, its life history traits have yet to be characterized in the northern hemisphere. Thus, the age, growth, maturity, spawning season, sex structure, and sex reversal of this species were investigated for the first time in the subtropical Yaeyama region, Japan. According to the age composition of the sexes and the structure of the gonads, this species displayed diandric hermaphroditism with a primary male. The maximum fork length and ages of females, primary males, and secondary males were 506 mm and 17 years, 537 mm and 12 years, and 578 mm and 13 years, respectively. The estimated parameters of the von Bertalanffy growth function for all specimens were L∞=562, k=0.18, and t0=−0.81. The spawning season in the Yaeyama region was estimated to be between April and October according to the gonadal development of both sexes. Compared with previous studies on this species conducted in tropical waters, the Yaeyama population in subtropical waters lives longer, grows larger, and matures and changes sex later. However, previous studies in subtropical waters have shown similar life history parameters as those observed in this study, and spawning was inactive during the low water temperature periods. These features suggest that vulnerability to fishing pressure would be higher in subtropical populations than in tropical populations. This study also confirmed that H. longiceps has an obvious spawning period when the average water temperature is ≥24.6°C. The unique features of H. longiceps in the Yaeyama region are thought to reflect the lower temperature of the region’s subtropical waters. These findings suggest that the future effects of global warming could extend the spawning season of subtropical H. longiceps populations.