Social Organization and Spawning Behavior of the Pteroine Fish Dendrochirus zebra at Miyake-jima, Japan

Abstract

Social organization and reproductive behavior of the lionfish Dendrochirus zebra were studied at Miyake-jima, one of the Izu Islands of Japan.Individuals of this species are solitary predators that hunt over wide home ranges that overlap greatly with other members of the species, both male and female.Large males are often found within specific areas in the midst of their much wider home ranges.Such “activity centers”are not defended, and cannot be considered as territories.During daylight, females in spawning condition come to specific locations, termed“rendezvous sites”, within the activity center of a particular male, where they are met by that male or by one of many smaller subdominant males.Spawning occurs after sunset in areas of moderate off-shore currents.Males compete for females, often fighting.Wounds inflicted by venomous spines of rival males can result in injury that may affect the spawning success of the injured male.
Females spawn two mucous sacks, each containing a few thousand eggs.These are released after a short upward dash.Tests showed that many well-known egg predators were repulsed by the mucus.It is hypothezied that the upward spawning rush is an anti-predator defense, and that certain fish, perhaps sharks, might occasionally prey on lionfishes.