LHRHA AND PIMOZIDE-INDUCED SPAWNING OF ASIAN CATFISH CLARIAS-MACROCEPHALUS (GUNTHER) AT DIFFERENT TIMES DURING AN ANNUAL REPRODUCTIVE-CYCLE

Captive Clarias macrocephalus were induced to spawn during the off-sea son (February), before (May), during (August) and end (November) of th e natural breeding period to test their seasonal responsiveness to hor mone treatment, and assess the resulting egg and larval quality. Intra muscular injections were given to five fish in each treatment consisti ng of 0.05 mu g LHRHa + 1 mu g PIM g(-1) body weight (BW), 0.05 mu g L HRHa, 1 mu g PIM, or LHRHa vehicle (0.9% NaCl) and PIM vehicle (1 dime thylsulfoxide: 9 propylene glycol, v/v). At any phase of the annual cy cle, only fish injected with a combination of LHRHa and PIM spawned, a lthough initial egg size was similar among fish within a season. Howev er, initial egg size was largest in fish induced to spawn in May (1.59 mm), followed by fish induced in August and November (1.54 mm), and s mallest in fish induced in February (1.49 mm). All fish ovulated when induced to spawn in May and August, but ovulation rates decreased to 8 0% and 60% when fish were injected in November and February, respectiv ely. Catfish induced to spawn in May, August and November had higher e gg production, fertilization and larval survival rates than the fish i nduced in February. Hatching rates were higher in fish induced in May and August than in February, while hatching rate of fish induced in No vember was similar to those spawned at other times of the year. These results provide useful information regarding the broodstock management and hatchery production of C. macrocephalus.