Reproductive traits of deep-sea snappers (Lutjanidae): Implication for Okinawan bottomfish fisheries management

We examined the reproductive cycle, sexuality, and length at 50% maturity (L50) of the deep-sea snappers Etelis coruscans, Paracaesio caerulea, Pristipomoides filamentosus, and Pr. sieboldii from Okinawan waters based on gonadal histology. The overall sex ratios of E. coruscans and Pr. sieboldii were significantly female-biased, whereas those of Pa. caerulea and Pr. filamentosus were not significantly sex-biased. The spawning season was estimated to occur from May to November for E. coruscans, from April to September for Pa. caerulea, and from March to October for Pr. filamentosus and Pr. sieboldii. Their initial reproductive activity coincided with an increase in sunlight duration. Of the four species examined, E. coruscans and Pr. filamentosus indicated significant peaks of spawning around a specific lunar phase. We observed the presence of multiple oocyte maturation stages with postovulatory follicles (POFs) during the spawning season of each species. Transitional gonads were not observed in these four snappers. The L50 of the females and males were 67.1 cm fork length (FL) and 37.6 cm FL for E. coruscans; 34.8 cm FL and 26.1 cm FL for Pa. caerulea; 35.7 cm FL and ≥20.0 cm FL for Pr. filamentosus; and 24.6 cm FL and ≥24.0 cm FL for Pr. sieboldii, respectively. Thus, the reproductive traits of E. coruscans, Pa. caerulea, Pr. filamentosus and Pr. sieboldii are characterized by a long spawning season and iteroparity. The E. coruscans and Pa. caerulea show relatively slow maturation compared to the two species of Pristipomoides. The implications of our results vis-à-vis the conservation and management of Okinawan bottom fisheries are discussed.