Abstract
Ovarian development e. g. gonadosomatic index, oocyte diameter, fecundity, histology, and related steroid hormones e. g. testosterone (T), estradiol-17β (E2), 17α, 20β-dihydroxy-4-pregnen-3-one (DHP), were examined in captive female catfish Clarias macrocephalus during an annual cycle to establish the optimum season for its artificial propagation. Results showed that captive C. macrocephalus had a group-synchronous pattern of ovarian development, as indicated by the presence of oocytes at all stages of development throughout the annual cycle. Mean gonadosomatic index (GSI; 11-13%), oocyte diameter (1.54-1.56mm), fecundity (80-110 eggs/g body weight), and serum T levels (36-37 ng/ml) were lowest in January-April, suggesting that it is not the optimum season to induce C. macrocephalus to spawn during these months. Serum E2 levels were lowest in January (7 ng/ml), and highest in December (20 ng/ml). Serum DHP levels were below detectable limits (<0.02 ng/ml) throughout the year, supporting the observation that final maturation and ovulation do not occur in this species under captive conditions. Changes in various reproductive parameters and steroid hormone levels indicate that January-March, April-June, July-September and October-December correspond to the refractory, preparatory, spawning and post-spawning periods, respectively, of the annual cycle. The results of the present investigation can be used as a guide for the controlled breeding and commercial aquaculture of C. macrocephalus in the Philippines.
