Seasonality of the reproductive cycle of female Heterobranchus longifilis in tropical pond culture

Abstract

The aim of this study was to monitor the reproductive cycle of female Heterobranchus longifilis under tropical pond conditions in order to optimize controlled spawning. Three experimental groups were set up: The first group (I) consisted of adult females transferred from their natural habitat to ponds. The second experimental group (II) consisted of breeders that adapted to husbandry conditions for at least one year. The third set of females (III) was produced under hatchery conditions. Females of the natural population served as controls. Over a one year period blood samples were taken from the individually marked females on a biweekly basis. If ripe eggs were found at the sampling time, females were stripped, the eggs were fertilized and hatched artificially. None of the feral breeders that were transferred to ponds during their natural breeding season could be stripped during that year. The breeding season of both groups II and III started in February. Seasonal changes in egg output showed a maximum between April and July. Egg production of group III was generally higher. The time interval between two strippings of the same female was 6 weeks. Viable eggs were obtained from the adapted feral breeders until August, whereas the breeding season of the hatchery-raised females extended to October. Two thirds of the hatchery-raised females were stripped four or more consecutive times. Throughout the entire season high hatching rates of normal larvae were obtained. Seasonal profiles of the gonadal steroids testosterone and estradiol-17β reflect the annual changes in sexual activity of female Heterobranchus longifilis in tropical pond culture, exhibiting maximum values during the breeding times of each group and being lowest during resting periods.