Diurnal patterns of movement and feeding for an unfished population of Actinopyga echinites (Jaeger, 1833) in a protected marine sanctuary on Ningaloo Reef, northwestern Australia

Sea cucumbers are large conspicuous invertebrates that play an important functional role in coral reef ecosystems through bioturbation and organic load recycling making their abundance and movement patterns key features to understanding impacts on the benthos. This study examines the diel movement patterns of an unfished population of the commercially important sea cucumber, the deep-water redfish (Actinopyga echinites), within a fully protected marine sanctuary on the Ningaloo Reef, Western Australia. Movement rates were measured using long-run underwater stereo-video, while density was measured using belt transects. The size of A. echinites was also investigated. We observed abundances of A. echinites (1.58 individuals / m²) that far exceeded those from areas with fishing pressures. The majority of A. echinites were in the 150-175 mm size range, with no individuals less than 100 mm recorded. We quantified the movement patterns of 92 individual sea cucumbers which correlated with light intensity throughout a 24-hour period, where maximum mean movement rates occurred at 1:00 pm (75.7 cm / hour) before slowly decreasing with reduced light intensity. Actinopyga echinites specimens were primarily stationary between midnight and 7 am and were stationary and non-feeding approximately 22 % of the time. Most of the time (68 %) A. echinites were classified as non-stationary and feeding and significantly more active during the day. We discuss the abundance and size of A. echinites in relation to studies from other areas and relate their diurnal movement patterns to diel foraging theory.