Feeding sites frequentation by the pink whipray Himantura fai in Moorea (French Polynesia) as determined by acoustic telemetry
This study examines the frequentation of feeding sites by the pink whipray (Himantura fai) in the lagoon of Moorea (French Polynesia) from April 2005 to March 2006. Six multidirectional hydrophones (VEMCO VR 2) were deployed at 1.5-3 m depth in the North-western area of the Moorea lagoon in which two ray feeding sites were set up for tourism purposes in 1995 and 1999. The study area (1.9 km2) is part of a marine reserve created by the French Polynesian government in October 2004. Fourteen individuals (6 males, 8 females; disc width DW: 73-114 cm) were surgically implanted with individually coded ultrasonic transmitters (VEMCO V8-SC and V13-1H) and presence/absence data were collected for up to 340 days. One ray was never detected. Of the other 13 animals, 7 (4 males, 3 females) showed a maximum presence time on one feeding site (Sand bank) and 4 (1 male, 3 females) favoured the other one (Motu); 2 rays (1 male, 1 female) were detected less than 10% of their total detection time at either of the feeding sites. Both receivers located on the feeding sites detected all 12 individuals during the data collection period and detected a fish an average of 89% of the time daily, whereas the mean daily detection time of the other four receivers - located outside of any feeding arearanged from 27 to 60%. Only one ray was detected by all 6 receivers in the same day. We observed different frequentation patterns between individuals at each feeding site. Daily bimodal pattern related to feeding time is shown but with no correlation with tourist or feeding numbers. Rays show anticipation on feeding times (one or two hours before feeding hours) but they are conditioned and come on sites with or without feeding activity occurring on the selected day. Even if our study suggests that site fidelity exists for 11 individuals out of 13, the long-term impact of feeding on ray behaviour, reproduction and health still needs to be explored.