The purpose of this study was to determine the study of aspects of reproductive biology of manggabai fish (Glossogobius giuris). The method used is the observation method, where all fish are observed directly in the field for some characteristics of gonad maturity, while other observations are carried out in the laboratory. The parameters measured and observed are gonadal maturity level, gonadal maturity index, egg diameter, and fecundity of manggabai fish. Manggabai fish used during the study amounted to 50 heads consisting of 25 males and 25 females with a body length range 16.3 – 25.1 cm and body weight 26.66 – 48.24 grams. The results showed that the largest manggabai fish TKG was obtained at TKG I which was 32% (male) and females at TKG III were 36%. TKG greatly affects the IKG value, both in male and female fish. The highest IKG value of manggabai fish for female fish is in TKG IV with IKG values of 6.272% and for male fish 0.574%. Manggabai fish egg diameter reaches a length of 0.30 – 0.68 mm, width 0.07 – 0.10 mm with a weight of 0.08 mm. the fecundity of manggabai fish with gonad 4.09gr weight reached 3,172 eggs while gonad weight was 0.35gr with a range of 1,196 eggs.

Keywords : reproductive biology, manggabai fish (Glossogobius giuris).