Reproductive biology, growth, and age composition of non-native Indian glassy fish Parambassis ranga (Hamilton, 1822) in Haebaru Reservoir, Okinawa-jima Island, southern Japan

Age composition, growth, and reproductive biology of the non-native Indian glassy fish Parambassis ranga (Hamilton, 1822) were surveyed in the Haebaru Reservoir on Okinawa-jima Island, southern Japan. Standard lengths (SLs) of males and females ranged from 19.7 to 44.0 mm and from 19.2 to 52.4 mm, respectively. The overall sex ratio was significantly female-biased, with the monthly percentage of females ranging from 71.4 to 100.0. Marginal growth analysis of sectioned otoliths revealed opaque zones formed annually from November to May. Observed age ranged from 0 to 3 years for both sexes, although the 1-year age class comprised the majority of the sampled population. Von Bertalanffy growth parameters were L8 = 48.8 mm (SL), K = 0.43 year-1, and t0 = -1.47 years for males, and L8 = 43.7 mm, K =0.72 year-1, and t0 = -1.29 years for females. Length at 50% maturity was estimated to be 25.8 mm SL, and maturation was within 1 year after hatching. The main spawning season of P. ranga was estimated to occur from February to October, peaking in April.