Individually-unique Spot Patterns of Young-of-the-Year Giant Sea Bass (Stereolepis gigas) in Captive-raised Fish

Abstract

Young-of-the-year Giant Sea Bass (Stereolepis gigas) (hereafter YOY GSB) spend the first several months after planktonic settlement within recreational dive limits. After settlement, YOY GSB morph through pigmentation phases where patterns of black spots unique to individual fish appear against the fish's lighter background. In order to prove that underwater photographs of spot patterns could be used to individually identify and possibly track YOY GSB in the field, several YOY GSB were captured and raised at public aquaria. Both sides of each fish were planned to be photographed monthly for a year from the capture date. The black spots of YOY GSB are so few and distinct that computer programs developed to discern individuals of species with complicated spot patterns were not necessary for re-identification of individuals. Three fish that were followed for twelve months in captivity could be individually identified by comparing photographs of their spot patterns by eye. A fourth fish that survived for six months could also be individually distinguished through photographs. This is the first published study to follow the development of YOY GSB spot patterns. Underwater photo-identification techniques could be used to re-identify individuals from several months to at least a year after planktonic settlement. That no capture-recapture studies have been conducted on YOY GSB to date hinders the basic understanding of species ecology and population dynamics. This study opens the door to the use of underwater photography as a passive mark and recapture method for studying YOY GSB along soft-bottomed nursery beaches where they can be found for the first few months after settlement.