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Abstract

Spawning of the two Indian major carps, rohu (Labeo rohita) and mrigal (Cirrhinus mrigala) could be induced by fish gonadotropin releasing hormone (GnRH) purified from murrel (Channa punctatus) hypothalamus. The ‘Linpe’ method i.e., GnRH plus a dopamine antagonist, pimozide, was used in combination with Ca2+. Channa GnRH (cGnRH) was injected in two different doses, 10 or 20 μg per kg body weight in combination with pimozide (1 mg per kg) and Ca2+ (300 μg per kg ) with an interval of 6 h. Induced spawning occurred in all six sets at the same time while control fish failed to spawn. The total number of eggs product was approximately 30 000–35 000 in mrigal and 50 000⧹260 000 in rohu. Percent of fertilized eggs in rohu was about 80% whereas it was about 90% in mrigal.The above mentioned combination of cGnRH, pimozide and Ca2+, was used to test germinal vesicle breakdown (GVBD) in catfish (Clarias batrachus) and perch (Anabas testudineus). Oocyte diameter was significantly increased in catfish (from 0.71 ± 0.08 to 1.03 ± 0.05 mm, P <0.005) and in perch (from 0.46± 0.03 to 0.74± 0.09 mm, P < 0.01) at 36 h in response to above mentioned treatment. Oocyte diameter remained unaltered in control fish. In catfish, 82% GVBD occurred between 40–44 h while in perch 67% GVBD could be noticed between 50–56 h in the treated fish. GVBD did not take place in control catfish and perch till after 10 days of observation. Results indicate that use of cGnRH in the ‘Linpe’ method with Ca2+ is highly satisfactory for induced breeding of Indian major carps and final maturation of catfish and perch ovary.