Seasonal changes of gonadal activity of invasive vermiculated sailfin catfish (Pterygoplichthys disjunctivus) from Polgolla reservoir in Sri Lanka

The present study elucidates the pattern of the reproductive activity of the invasive Pterygoplichthys disjunctivus male (n = 113) and female (n = 124) fish in Polgolla Reservoir, Sri Lanka. The reproductive activity was studied based on the gonadosomatic index (GSI), macroscopic and microscopic features of the testes and ovaries, and the serum testosterone and progesterone level during a 12-month study period. The monthly GSI of male fish (P = 0.0001) was the highest (0.333 ± 0.08%) in October and the lowest (0.044 ± 0.01%) in January whereas in the female fish, the GSI was not changed significantly (P = 0.1780) during the 12-month period of sampling. The mean monthly serum testosterone concentration (P = 0.0244) was the highest (0.396 ± 0.332 ng/ml) in March and the lowest (0.085 ± 0.156 ng/ml) in August, while the mean serum progesterone concentration of female fish showed no significant difference (P = 0.4798). Histological examination revealed that the testes with seminiferous tubules filled with sperm and the ovaries with mature oocytes were present throughout the year. Therefore, based on the results of histology and reproductive characteristics, we concluded that both male and female P. disjunctivus in Polgolla Reservoir are breeding throughout the year.