Reproductive characteristics of the hermaphroditic four-finger threadfin, Eleutheronema tetradactylum (Shaw, 1804), in tropical coastal waters

Abstract This study investigates reproductive traits of the hermaphroditic four-finger threadfin, Eleutheronema tetradactylum , along the coasts of Thailand during January 2021 and January 2022. Fish sample from Pattani Bay, Thailand was collected to assess sex ratio, gonadosomatic index (GSI), maturity stage and fecundity. Additional samples from other provinces were used to investigate length and weight at first sex change (Ls 50 and Ws 50 ) and length at first maturity (Lm 50 ). It was found that the overall sex ratio for male and female was 1:0.69 with male predominated throughout the year. This fish spawned the whole year round with peak during moderate rainy season. Results from histological examination confirmed its protandrous hermaphrodite posing multiple spawning behavior. The average fecundity was 1.85 x 10 5 ± 1.05 x 10 5 eggs and positively related with standard length, body weight, gonad weight and egg diameter (P < 0.05). The Ls 50 and Ws 50 for fishes from Pattani Bay and Samut Prakan province were 27.58 cm, 419.39 g and 29.71 cm, 457.28 g, respectively. The Lm 50 of male from Pattani Bay and Samut Prakan were 25.78 cm and 25.56 cm, respectively, considered larger than those from Satun and Nakhon Sri Thammarat provinces. The Lm 50 of female from Pattani Bay was slightly smaller than that of Samut Prakan province. This study provides fundamental information on the reproductive characteristics of E. tetradactylum and can be implemented for both management of natural fish stock and future aquaculture development.