Diel movement patterns of the Hawaiian stingray, Dasyatis lata:: implications for ecological interactions between sympatric elasmobranch species

The Hawaiian stingray, Dasyatis lata, is a common benthic elasmobranch in nearshore Hawaiian waters. Acoustic telemetry was used to track the movements of seven rays in Kaneohe Bay, Oahu, Hawaii. Rays were tracked continuously over 31-74 h periods. Geographical movements were analyzed to determine space utilization and rate of movement. Rays were found to utilize significantly larger activity spaces at night (0.83 +/- 0.70 km(2)) (mean +/- SD) than during the day (0.12 +/- 0.15 km(2)). Mean total activity space for rays tracked was 1.32 +/- 0.75 km(2). Rates of movement were also significantly higher at night (0.34 +/- 0.30 km h(-1)) than during the day (0.15 0.22 km h-1). Average straight-line swimming speed was 0.64 +/- 0.16 km h(-1), with a maximum observed swimming speed of 1.9 km h(-1). Tidal stage had no effect on rate of movement. Comparison with previously published data on juvenile scalloped hammerhead sharks, Sphyrna lewini, in Kaneohe Bay revealed a high degree of overlap in habitat use and time of activity, suggesting possible ecological interactions between these two species.