Reproductive Behavior of the Giant Sea Bass, Stereolepis gigas

Aspects of the reproductive behavior of giant sea bass, Stereolepis gigas, were observed and monitored at Goat Harbor, Santa Catalina Island, CA from June 2014 to August 2015. The site was visited daily during the summer months, which is the assumed spawning season and aggregations were not present during the spring and fall months (October - March). Numbers of giant sea bass ranged from 2 to15 individuals at Goat Harbor. Six individuals were tagged with Vemco V13 tags to determine site fidelity of giant sea bass at Goat Harbor. All 6 were detected at the aggregation site on a daily basis throughout the summer months (July - September) and also detected at the nearby sites of Long Point and Empire Landing. Giant sea bass produced booming sounds, which were often associated with aggressive behavior, but may also to be associated with spawning. Drumroll chorusing also was recorded at the giant sea bass aggregation with two different frequencies 250 Hz and 350 Hz and may be used to attract mates similar to other fish species. These sounds, although not confirmed as giant sea bass vocalizations, coincide with peak giant sea bass activity (1900-2200 hrs) when they are moving about the water column rather than being stationary near the substratum. These vocalizations are not vii known to be associated with any other fishes in the immediate area, supporting the hypothesis that they are produced by giant sea bass. Courtship was observed during the late afternoons and was most prominent around dusk (1900-2100). Courtship involved sexual dimorphic color change, and displays such as circling in pairs and the nudging of the abdominal area of the presumed female by the snout of the presumed male. The courtship behaviors observed were similar to those observed of giant sea bass in captivity. Although spawning was not observed the available evidence suggests that spawning occurs just after dusk. Confirmation of spawning at or near the aggregation site was obtained through DNA barcoding with COI primers of eggs sampled from Goat Harbor. This study has given insight into courtship behavior and how to identify giant sea bass spawning aggregations in the wild, which is crucial for the management of the species.