Ecology and conservation of Irrawaddy, Orca Ella Brevirostris and Indo-Pacific Humpback, Sousa Chinensis, Dolphins in Cowie Bay, Sabah, Malaysia

• Main Author: Julian Ransangan
• Format: Report
• Language: English
• Published: Universiti Malaysia Sabah
• Subjects: SH Aquaculture. Fisheries. Angling; Cowie Bay; Pacific; Orca
• Online Access: http://eprints.ums.edu.my/id/eprint/23252/; http://eprints.ums.edu.my/id/eprint/23252/1/Ecology%20and%20conservation%20of%20Irrawaddy.pdf; http://eprints.ums.edu.my/id/eprint/23252/6/Ecology%20and%20conservation%20of%20Irrawaddyi.pdf

Between April 2008 and March 2009, 47 days of boat surveys were conducted off Cowie Bay, Sabah with the aim of recording dolphins' distribution during neap and spring tides. Data on dolphin sightings and physiochemical properties of water were collected in every tide cycle for a period of four consecutively days in 39 sampling zones. There are two species of dolphins inhabiting Cowie Bay namely the Irrawaddy (Orcaellabrevirostris) and Indo-Pacific humpback (hereinafter humpback) (Sousa chinens;s) dolphins. Currently, there is limited information regarding dolphins' species in Malaysia. Therefore, this study was carried out to generate information and provide understanding on the ecology and conservation of the two species dolphin in the area where the conservation status is poorly available. Irrawaddy dolphins were found in 43 surveys (91.5 %) and their sighting frequencies were highest in Zone 3 with 183 sightings (30.81 %). Feeding behaviour of Irrawaddy dolphins was most frequent (50.25% of sightings) compared to socializing (28.42 %) and travelling (12.09 %). The occurrence of Irrawaddy dolphins was correlated with sea surface temperature (SST) and turbidity, and the same goes to feeding and socializing. While, Humpback dolphins were found in 41 surveys (87.2 %) and their sighting frequencies were highest in Zone 3 (near the Seranum River) with 226 sightings (28.36 %). This species spent more time for feeding (59.49 %) than socializing (38.93 %) and travelling (10.82 %). Occurrence and behaviour of humpback dolphins did not correlate with depth and any of the water parameters. Both species can tolerate the same water conditions in the study area. Humpback and Irrawaddy dolphins are mostly found near river mouth. Based on the high feeding activity recorded throughout the study period, Cowie Bay could be an important feeding ground for the two dolphins' species. Hence, it is recommended that socio-economic activities, such as logging, agriculture and fisheries, which are actively taking place in the study area be controlled to minimize threats. Such effort can largely contribute to the restoration of the dolphin populations and other marine life in the bay.