Spawning Behavior of the Dolphin, Coryphaena hippurus, in the Aquarium and Its Eggs and Larvae

Abstract

Thirty-six specimens of the dolphin, Coryphaena hippurus Linnaeus, 35 to 50cm in total length, were collected during September to October, 1975, off the coast of Kamogawa, Chiba Prefecture, Japan.They were kept in a big tank (17m×12m×3.5m).The water temperature in the tank was controled between 22.8°C and 25.4°C.
Eleven specimens survived to grow up about 100cm in total length when their breeding behavior was observed.At the time when the first spawning was found, 8 specimens were survived.Twenty times of spawnings were observed from April 22 to July 13, 1976.The spawning was taken place mainly at the water surface by a pair of adults, although the pair was often accompanied by one to three dolphins.Every spawning occurred between 15: 35 and 17: 45.
Fertilized eggs are transparent, floating, and spherical in shape, 1.40 to 1.65 mm in diameter.The eggs hatched out about 60 hours after fertilization at 24 to 25°C.
The newly hatched larvae were 3.8 to 4.9 mm in total length.In 4 days after hatching the larvae began to eat Brachionus plicatilis.But all of them died within 9 days after hatching.