A note on the species occurrence, distributional ecology and fisheries interactions of cetaceans in the Mergui (Myeik) Archipelago, Myanmar

Abstract

A vessel-based line-transect survey for cetaceans conducted during 23 February-6 March 2005 of the nearshore waters (to a depth of 40- 60m) of the Mergui (Myeik) Archipelago of southern Myanmar searched along 955km of trackline resulting in 30 cetacean sightings. These included Indo-Pacific bottlenose dolphins Tursiops aduncus (n=15), Indo-Pacific humpback dolphins Sousa chinensis (n=3), spinner dolphins Stenella longirostris (n=4; the largest of these was mixed with pantropical spotted dolphins Stenella attenuata), Irrawaddy dolphins Orcaella brevirostris (n=1), finless porpoises Neophocaena phocaenoides (n=1), Bryde’s whales Balaenoptera edeni/brydei (identification tentative; n=1), one unidentified baleen whale (probably also a Bryde’s whale) and four unidentified delphinid groups. Irrawaddy dolphins and finless porpoises were found in shallow, brackish waters, Indo-Pacific humpback dolphins also in shallow waters but those less affected by freshwater inputs and Bryde’s whales and Indo-Pacific bottlenose, spinner and spotted dolphins in deeper and clearer waters. In total 2,565 gill netters/long liners (95% CI=1,228-3,903), 1,301 squid jiggers (95% CI=611-1,992) and 532 stern trawlers (95% CI=154-910) were estimated to be operating in the study area. Concentrations of gill netters/long liners were particularly high in shallow nearshore waters and at least 150 were operating in the bay where the only sightings of Irrawaddy dolphins and finless porpoises were made. There is a need to better assess nearshore cetacean populations, investigate whether or not incidental and intentional catches are sustainable and incorporate a cetacean element into an initiative to establish a marine protected area network in the Mergui Archipelago.

Species occurrence and distributional ecology of nearshore cetaceans in the Bay of Bengal, Bangladesh, with abundance estimates for Irrawaddy dolphins Orcaella brevirostris and finless porpoises Neophocaena phocaenoides

“…The result of the GAM of environmental preferences for Irrawaddy dolphins is consistent with qualitative descriptions in the literature. Within their coastal range outside of Bangladesh, most sighting records of Irrawaddy dolphins have been associated with low-salinity and shallow waters near river mouths: the Brunei, Baram, Batang, Kumay, Kendawangan, Kinabatangan and Sarawak rivers of Borneo Indonesia, Malaysia and Brunei (Banks, 1931;Beasley and Jefferson, 1997;Dolar et al, 1997;Gibson-Hill, 1950;Mörzer Bruyns, 1966;Perrin et al, 1996;Pilleri and Gihr, 1972;1974;Rudolph et al, 1997;Weber, 1923); the Belawan Deli River of northeastern Sumatra and various rivers along the southwestern coast of Irian Jaya, Indonesia (Mörzer Bruyns, 1966); the Chao Phraya, Mae Nam Chin, Chanthaburi and Pattani rivers of Thailand (Chantrapornsyl et al, 1996); the Myebone, Kalidan and Kyaukpyu rivers of the Rakhine (Arakan) coast of Myanmar (Smith et al, 1997b); the Kyaukpya and Tennasarim rivers of the Mergui Archipelago in Myanmar (Smith and Than Tun, 2008); and in freshwater-affected areas of Malampaya Sound in Palawan, Philippines (Dolar et al, 2002).…”