Abstract
Observations made on the reproductive behavior of Glossogobius olivaceus in a glass aquarium gave the following results.With almost no courtship behavior, ritual fighting, nor struggle for a nest, a male and a female goby make a couple to start nesting in an artificial nest, a wooden box.A fish sometimes changes its partner after once being made separate from another.Before oviposition, which takes place 10 hours to 5 days after a start on nesting, a series of pseudo-ovipositing behavior is seen.Then, swimming supinely in the nest, the female and the male goby emit eggs and sperm alternately.This lasts for about 1.5-3.5 hours.The eggs which amount to about 60, 000 in number adhere unistratally to the surfaces inside the nest, and hatch out about 80 hours after spawning at a water temperature of 25.5-26.5°C.In general the male goby stays in the nest to guard the eggs.There are, however, some males which repeatedly leave their nest for some time, for 3 hours at the longest.On the other hand, the gobies seem rather insensible to disturbances of the nest and seldom eat their own eggs even after the nests were roughly treated for counting or photographing.
