Locomotor activity, track and pattern of movement over 24 hours of the crab portunus pelagicus (Linnaeus) in a sub-tropical tidal passage

A study of the movement of Portunus pelagicus (Linnaeus) using ultrasonic tags was carried out in a tidal passage, southern Queensland, Australia (27 °00’E, 153 °00’S). Patterns of movement were consistent with `loose’ homing involving medium-term residency within a temporary foraging area. The area utilised by an individual crab was variable averaging 81,592m (SD = 74,409m2, n = 6), as was its average rate of movement at 0.8m min’ to 3.7m mint. A preference for a submerged tidal mudflat was observed and there was some evidence of tidal current assistance in movement around the foraging area. The maximum rate of movement was 23m min’, probably assisted by tidal streaming. No pronounced temporal activity pattern was observed, in contrast to that observed in laboratory studies and offshore trawl data. This was explained by the interaction of tidal periodicity with previously observed diurnal activity patterns.