Multiple gonadal maturation and re-maturation after hormone-induced spawning in bighead carp Aristichthys nobilis Rich.

Abstract

Gonadal maturation and rematuration after hormone-induced spawning in cage-reared female bighead carp Aristichthys nobilis were observed. Percent maturation ranged from 54 to 100% for females and 0 to 40% for males. Maturation rates in either sex were high during March (1988) and low during December (1987). No significant differences were observed for monthly mean oocyte diameters ranging from 1.41 to 1.51 mm. Of the 34 females injected with LHRH-a, Domperidone or HCG, either singly or in combinations, 12 females spawned successfully. Three females were spawned twice consecutively at intervals between 71 and 107 days. Fish possessed oocytes of similar characteristics as those obtained from pre-spawning females when sampled after 27 days from spawning. Generally, oocyte diameters of individual fish measured before the first spawning (range: 1.41 to 1.53 mm) were not significantly different from those measured during the succeeding spawnings (range: 1.38 to 1.49 mm). Physico-chemical and biological parameters in the lake did not influence maturation except for zooplankton.