Successful Artificial Breeding of the Mekong Giant Catfish (Pangasianodon gigas, Chevey) Reared in Earthen Ponds by Boostering with Gonadotropin Releasing Hormone Analogue (GnRHa)

Abstract

Ten-year-old Mekong giant catfish (MGC) held in captivity were divided in three treatments. Treatment 1 served as the control, treatment 2 was injected once a week with gonadotropin releasing hormone analog (GnRHa) 50 µg•kg-1 and treatment 3 was given 100 µg•kg-1 during the spawning season (May-July, 2002). The highest level of Testosterone (T) in male occurred seven days after injection, but the highest Estradiol (E2) level in female occurred fourteen days after the first injection. The T and E2 levels post-injection were respectively significantly different (P<0.05) compared with the levels before injection. Before the spawning season, T and E2 were 800 ng•ml–1 in the males and 3,179 pg•ml-1 in the females, respectively. During the first and second weeks after injection, the T and E2 levels continued to increase. The male MGC achieved greater and earlier maturation than the females. More sperm density was also observed in treatment 2 and 3 as compared with the control. Better fecundity was also observed in treatment 2. We succeeded in lowering the age at which spawning and fertilization occurred by injecting the fish weekly with GnRHa. This technique will prove useful in captive breeding of MGC to increase the wild population of this endangered species in the Mekong River.