Abstract

• Amphidromous croaker Johnius coitor (Hamilton, 1822) is one of the commercially important demersal fish of the Gyaing River segment between Gadoe and Kawbein Area. The irregular pattern of GSI and HSI of studied species were now an evidence of potential indicator which directly reflect the hazard conditions of aquatic medium. Macroscopic and microscopic studies were made on the gonadal development of this species, J.coitor. Microscopic study for male spermatogenesis were identified into four stages; spermatogonia phase, spermatocyte phase, spermatid stage and spermatozoa stage. For oogenesis, oocytes were identified as chromatin nucleolus phase, prenucleolus phase, primary yolk phase, secondary yolk phase, tertiary yolk phase, germinal vesicle migration phase, germinal vesicle breakdown phase and spent phase. The female gonadal developmental stages will be compared with that of “oocytes ranged from 13.10µm to 520.40µm in Johnius coitor. Thus, this study suggested to take necessary steps are needed to monitor the aquatic medium to protect the fish reproductive physiology, thus fish population as a whole. These findings are very important to fishery management to fix closed season and closed areas for conservation of fish. Suggestions for future works outlined.