Sexual reproduction of the Hawaiian black coral Antipathes griggi (Cnidaria: Antipatharia)

Abstract

The Hawaiian black coral fishery has maintained steady catch levels for over 50 years. However, recent declines in the biomass of commercially valuable Hawaiian black corals question whether regulations need to be rede- fined for sustainable harvesting. Fishery management efforts are complicated by the limited information on the basic life history and reproduction of black corals. To address this knowledge gap, we used histological techniques to investigate sexual reproductive processes within Antipathes griggi, the dominant species targeted by the fishery. Our results indicate that A. griggi is likely gonochoric with a 1:1 sex ratio and has an annual reproductive cycle. Furthermore, the percentage of polyps containing gametes dropped con- tinuously throughout the reproductive season, indicating that spawning occurs in successive events with greatest intensity between November and December. Current fishing regulations prohibit harvesting of colonies\90 cm in height in state waters, and colonies \120 cm in height in federal waters. This study indicates that *80% meeting the state harvesting limit, and *90% of colonies meeting the federal limit, are sexually mature. Therefore, increasing these minimum size harvesting limits would ensure that more colonies can reproduce before being exposed to fishing mortality. Although A. griggi can be found to depths of 100 m, it is rare below the 75 m depth limit at which com- mercial harvest occurs in Hawai'i. Thus, the supposed depth refuge from harvest does not really exist.