Site fidelity,size, and spatial arrangement of daytime home range of thumbprint emperor <Emphasis Type="Italic">Lethrinus harak</Emphasis> (Lethrinidae)

Although emperors (Lethrinidae) are commercially important fisheries resources in tropical and subtropical waters, their home range size and its spatial arrangement have not been sufficiently clarified. In the present study, the size and spatial arrangement of the daytime home range of the thumbprint emperor Lethrinus harak were investigated by using a portable GPS receiver. In a 150 m × 200 m quadrat, 21 individuals of the species were identified by their color pattern, and individuals were divided into four arbitrary size classes (class 1 < 20 cm TL ≤ class 2 < 25 cm TL ≤ class 3 < 30 cm TL ≤ class 4). Fish tracking by snorkeling was conducted with the portable GPS receiver. Daytime site fidelity of this species was high and there was a significant positive correlation between the home range size and fish total length. Home ranges of same-sized individuals abutted each other (20.3% area overlap), whereas those of different-sized individuals overlapped (48.3% area overlap). Agonistic behavior (attacking) occurred significantly more frequently between same-sized individuals than between different-sized individuals. These results suggest that daytime home ranges of Lethrinus harak can be regarded as territories against same-sized individuals, but not different-sized individuals.