Limited movement in blue rockfish Sebastes mystinus: internal structure of home range

Abstract

Home range has been estimated for a limited number of marine fishes; however, the use of space and timing of activities within the home range has rarely been studied. In addition, under- standing movement patterns of exploited fish species has been identified as a crucial science gap, impeding informed marine reserve design. We used a radio-acoustic positioning telemetry (VRAP) system to monitor detailed movements of 10 blue rockfish Sebastes mystinus around shallow rock pinnacles and stands of bull kelp Nereocystis leutkeana in central California in September 2002. The mean home range was 8783 m 2 ± 1137 SE; however, activity was highly concentrated in 1 to 3 core areas within each home range. Mean core areas measured 1350 m 2 ± 286 SE, but accounted for ~83% of activity. All core areas were centered over rock pinnacles where rockfish were highly aggregated. Individuals exhibited high site fidelity and made only brief radial excursions away from these centers or moved directly from one pinnacle to the next along defined corridors. Patterns of diel activity and nocturnal sheltering corresponded closely with nautical twilight. Cores overlapped, but estimated locations of nocturnal shelters differed significantly among individuals. Movement patterns were cor- related with wind velocity, upwelling index, water temperature and habitat structure.