Isabel Beasley

Irrawaddy dolphin Orcaella brevirostris in the Cambodian Mekong River: an initial survey

Irrawaddy dolphins Orcaella brevirostiris are found in coastal waters from the Bay of Bengal east to Palawan, Philippines and south to northern Australia. They also occur in three large tropical river systems in South-east Asia: the Mekong, Mahakam and Ayeyarwady. In March and May 1997 approximately 350 km of riverine habitat in parts of north-east Cambodia were surveyed, discussions took place with local people, and reported dry season dolphin habitat was mapped. Our objectives were to investigate the status, habitat and distribution of dolphins in north-east Cambodia and identify threats to the continued survival of dolphins in the Mekong River Basin. Nine groups of dolphins were observed in the Mekong River. A ‘best’ estimate of 40 animals were seen. Irrawaddy dolphins were generally confined to sections of the river with water levels >8–10 m during the dry season. It appears that the Mekong River dolphin population is rapidly declining. In 1997 there were probably no more than 100¨C150 dolphins left in north-east Cambodia (including southern Laos) and no more than 200 within the entire Mekong River Basin, although these numbers remain tentative. Anthropogenic mortality is high, albeit largely unintentional, and there is considerable risk that the dolphin population will become locally extinct in the Mekong River in the near future. The establishment of community-managed deep water Fish Conservation Zones with government support may represent the best opportunity for reducing dry season dolphin mortality from large-meshed gillnet entanglement. Efforts to establish protected areas for dolphins are currently underway.

Local assessments of marine mammals in cross-cultural environments

Biodiversity assessments by research scientists are often logistically difficult and expensive to implement in remote areas. Locally-based approaches have the potential to overcome some of these challenges by capitalising on the knowledge and capacity of local people. Many Indigenous people in northern Australia are custodians of coastal areas that support globally significant populations of tropical marine mammals, including coastal dolphins and dugongs. The objective of our study was to design and implement a locally-based approach in a cross-cultural environment to assess the distribution of marine mammals in the remote waters of the Gulf of Carpentaria, Northern Territory. The study was conducted as a partnership between Yanyuwa Aboriginal families, research scientists, government officers and the li-Anthawirriyarra Sea Rangers. We conducted a series of participatory mapping workshops to share and record local observations of dolphins and dugongs. These observations provided the longitudinal information required to inform the design of the first dedicated marine mammal vessel survey in the Gulf of Carpentaria. The vessel surveys found three species of dolphins present in the area (Australian snubfin, humpback and bottlenose dolphins), even though sightings were low; dugongs being much more common. We found that the integrative and locally-based approach built the capacity of both the li-Anthawirriyarra Sea Rangers and research scientists to assess the distribution of marine mammals. If replicated over longer time-frames and coordinated over broader spatial scales, information on distribution and abundance derived from locally-based approaches has the potential to inform the status of marine mammals.

Conserving Dolphins in the Mekong River: The Complex Challenge of Competing Interests

Publisher Summary Several attempts have been made to conserve the critically endangered population of Irrawaddy dolphins inhabiting the lower Mekong River. In January 2001, the Mekong Dolphin Conservation Project (MDCP) was initiated as part of the first authors PhD research at James Cook University, Australia. All activities were conducted in cooperation with the Cambodian Department of Fisheries, which was extremely supportive of all aspects of the project. Beasley was the full-time project manager for 4.5 years. All project activities were designed to contribute toward a comprehensive understanding of the dolphin population on which to base initiatives to ensure the populations long-term survival. The research results from the MDCP till April 2005, confirmed that the Irrawaddy dolphin population inhabiting the Mekong River is very small, declining, and facing continuing threats. In 2001, MDCP initiated a carcass recovery program throughout the lower Mekong River to collect and conduct necropsy on all dead dolphins and attempt to determine the cause of mortalities. At the end of 2002, MDCP conducted a large-scale awareness campaign about the importance of reporting dolphin carcasses. As a result of these efforts, dolphin carcasses were often reported within days of death from 2003 onwards.

Conservation Status of Marine Mammals in Cambodian Waters, Including Seven New Cetacean Records of Occurrence

The first dedicated, boat-based marine mammal surveys in Cambodian coastal waters were conducted over seven discrete survey periods, spanning February to September 2001. These surveys covered the majority of Cambodian coastal waters, in addition to the main offshore islands. As a result of these surveys, ten marine mammal species have now been confirmed to occur in Cambodian waters. Six of these, the false killer whale, a long-beaked form of common dolphin, pantropical spotted dolphin, dwarf spinner dolphin, Indo-Pacific bottlenose dolphin, and Indo- Pacific humpback dolphin, constitute new country records for Cambodia. Additionally, a short-finned pilot whale was found live-stranded, constituting a further new country record. These initial results indicate that the current status of marine mammals in Cambodian waters is encouraging, both in terms of species diversity and abundance. Cambodian waters appear to support regionally, if not globally, significant populations of several of these species. The dugong is almost certainly the most highly threatened marine mammal in the region. Studies to date have provided important baseline knowledge regarding the status, distribution, and important areas of occurrence for marine mammals in Cambodia. It is now essential that conservation and management strategies are developed and implemented. Public education and awareness and community-based management programs, as well as stricter laws, regulations, and adequate enforcement will be essential to conserving the remaining marine mammal populations and ensuring their survival in Cambodian coastal waters.

Observations on Australian Humpback Dolphins (Sousa sahulensis) in Waters of the Pacific Islands and New Guinea

The Australian humpback dolphin, Sousa sahulensis, has recently been described to occur in northern Australian coastal waters. However, its distribution in adjacent waters of the Pacific Islands and New Guinea remains largely unknown. Although there have been few studies conducted on inshore dolphins in these regions, the available information records humpback dolphins primarily from the Kikori Delta in Papua New Guinea, and Birds Head Seascape in West Papua. Research in southern Papua New Guinea indicates that humpback dolphins are indeed S. sahulensis, based on cranial and external morphometrics, external colouration and the preliminary genetic analysis presented here. A similar situation exists for the Australian snubfin dolphin, Orcaella heinsohni, where it is assumed that the species also occurs along the Sahul Shelf coastal waters of northern Australia and New Guinea. There are anecdotal reports of direct catch of Australian humpback dolphins for use as shark bait, coastal development is increasing, and anthropogenic impacts will continue to escalate as human populations expand into previously uninhabited regions. Future research and management priorities for the Governments of the Pacific Islands and Indonesia will need to focus on inshore dolphins in known regional hotspots, as current bycatch levels appear unsustainable.

Analysis of mitochondrial DNA clarifies the taxonomy and distribution of the Australian snubfin dolphin (Orcaella heinsohni) in northern Australian waters

Conservation management relies on being able to identify and describe species. Recent morphological and molecular analyses of the dolphin genus Orcaella show a species-level disjunction between eastern Australia and South-east Asia. However, because of restricted sampling, the taxonomic affinities of the geographically intermediate populations in the Northern Territory and Western Australia remained uncertain. We sequenced 403 base pairs of the mitochondrial control region from five free-ranging Orcaella individuals sampled from north-western Western Australia and the Northern Territory. Low net nucleotide divergence (0.11–0.67%) among the Australian Orcaella populations show that populations occurring in the Northern Territory and Western Australia belong to the Australian snubfin (O. heinsohni) rather than the Asian Irrawaddy dolphin (O. brevirostris). Clarifying the distribution of Orcaella is an important first step in the conservation and management for both species; however, an understanding of the metapopulation structure and patterns of dispersal among populations is now needed.

Demographic collapse and low genetic diversity of the Irrawaddy dolphin population inhabiting the Mekong River

In threatened wildlife populations, it is important to determine whether observed low genetic diversity may be due to recent anthropogenic pressure or the consequence of historic events. Historical size of the Irrawaddy dolphin (Orcaella brevirostris) population inhabiting the Mekong River is unknown and there is significant concern for long-term survival of the remaining population as a result of low abundance, slow reproduction rate, high neonatal mortality, and continuing anthropogenic threats. We investigated population structure and reconstructed the demographic history based on 60 Irrawaddy dolphins samples collected between 2001 and 2009. The phylogenetic analysis indicated reciprocal monophyly of Mekong River Orcaella haplotypes with respect to haplotypes from other populations, suggesting long-standing isolation of the Mekong dolphin population from other Orcaella populations. We found that at least 85% of all individuals in the two main study areas: Kratie and Stung Treng, bore the same mitochondrial haplotype. Out of the 21 microsatellite loci tested, only ten were polymorphic and exhibited very low levels of genetic diversity. Both individual and frequency-based approaches suggest very low and non-significant genetic differentiation of the Mekong dolphin population. Evidence for recent bottlenecks was equivocal. Some results suggested a recent exponential decline in the Mekong dolphin population, with the current size being only 5.2% of the ancestral population. In order for the Mekong dolphin population to have any potential for long-term survival, it is imperative that management priorities focus on preventing any further population fragmentation or genetic loss, reducing or eliminating anthropogenic threats, and promoting connectivity between all subpopulations.

Australian Snubfin Dolphin: Orcaella heinsohni

Abstract The Australian snubfin dolphin is a close relative of the Irrawaddy river dolphin and occurs largely in nearshore areas, as does the latter. It was only recently described as a separate species, largely by skull morphology and recent genetics.

Chapter 15 – Conserving Dolphins in the Mekong River: The Complex Challenge of Competing Interests

Publisher Summary Several attempts have been made to conserve the critically endangered population of Irrawaddy dolphins inhabiting the lower Mekong River. In January 2001, the Mekong Dolphin Conservation Project (MDCP) was initiated as part of the first authors PhD research at James Cook University, Australia. All activities were conducted in cooperation with the Cambodian Department of Fisheries, which was extremely supportive of all aspects of the project. Beasley was the full-time project manager for 4.5 years. All project activities were designed to contribute toward a comprehensive understanding of the dolphin population on which to base initiatives to ensure the populations long-term survival. The research results from the MDCP till April 2005, confirmed that the Irrawaddy dolphin population inhabiting the Mekong River is very small, declining, and facing continuing threats. In 2001, MDCP initiated a carcass recovery program throughout the lower Mekong River to collect and conduct necropsy on all dead dolphins and attempt to determine the cause of mortalities. At the end of 2002, MDCP conducted a large-scale awareness campaign about the importance of reporting dolphin carcasses. As a result of these efforts, dolphin carcasses were often reported within days of death from 2003 onwards.

Conserving Dolphins in the Mekong River

Publisher Summary Several attempts have been made to conserve the critically endangered population of Irrawaddy dolphins inhabiting the lower Mekong River. In January 2001, the Mekong Dolphin Conservation Project (MDCP) was initiated as part of the first authors PhD research at James Cook University, Australia. All activities were conducted in cooperation with the Cambodian Department of Fisheries, which was extremely supportive of all aspects of the project. Beasley was the full-time project manager for 4.5 years. All project activities were designed to contribute toward a comprehensive understanding of the dolphin population on which to base initiatives to ensure the populations long-term survival. The research results from the MDCP till April 2005, confirmed that the Irrawaddy dolphin population inhabiting the Mekong River is very small, declining, and facing continuing threats. In 2001, MDCP initiated a carcass recovery program throughout the lower Mekong River to collect and conduct necropsy on all dead dolphins and attempt to determine the cause of mortalities. At the end of 2002, MDCP conducted a large-scale awareness campaign about the importance of reporting dolphin carcasses. As a result of these efforts, dolphin carcasses were often reported within days of death from 2003 onwards.