The fresh-water goby, Odontobutis obscura (Temm. et Schl.) (belonging to the family Eleo- tridae), is very common in South-Eastern China. It lives in the bottom of lakes, streams and rivers. The food consists mainly of shrimps and small fishes. Sexes can be easily distingulshed from the shape and color of the urogenital papillae. At the beginning of the brecding scason, the male occupies a site as a nest, such as crevices between stones or rocks, large bivalved shells, brocken crockery, etc., at the depth of 1-2 m. and produced sound to attract females. The breeding season lasts from early April to early June (18-25℃.), about 60 days. Eggs are laid usually in early morning about 6-7 a. m. Each female spawns 1-3 times during the season according to its age. Eggs are lightly yellow in color, ovoid in shape, 2.10×1.63 mm. on averge. The number of eggs varies from 556 to 1647. The male guards in the nest and flaps constantly its fins in order to keep the water in the nest flowing. The incubation period lasts 25 days if the water temperature ranges from 15.5° to 28.5℃. and it lasts 19 days if the temperature is riased from 19°to 31℃. The development of cmbryo may be divided into 15 stages. Eggs hatch also in the early morning. The newly hatched fry about 0.70-0.75 cm. in length swims freely in the water and feeds on cyclops. The number of ossified annules on radials of the pectoral fins can be used for age determination. The ossified annules formed in the radials seems to occur in the late winter. Both sexes show a similar growth rate and longevity.