Seasonal occurrence and feeding habits of black marlin, Istiompax indica, around Yonaguni Island, southwestern Japan

Abstract

The seasonal occurrence of black marlin, Istiompax indica, around Yonaguni Island, southwestern Japan, was analyzed. Black marlin was abundant from April to July, and the majority of landed fish were female (97%). None of these females was reproductively mature. The condition factor of females increased from April to July. Of 56 black marlin examined, 21 individuals contained 12 prey species; the most important prey species was skipjack tuna, Katsuwonus pelamis, and one neonatal silky shark, Carcharhinus falciformis, was also found. These results indicate that the occurrence of black marlin off Yonaguni Island was associated with feeding and not with spawning.