A workshop on the assessment of Indo-Pacific bottlenose dolphins (Tursiops aduncus), with the Solomon Islands as a case study, took place from 21-23 August 2008 in Apia, Samoa. It was planned and organized under the auspices of the Cetacean Specialist Group and attended by 19 invited participants from eight countries.
Live-capture, holding in captivity and export of Indo-Pacific bottlenose dolphins from the Solomon Islands began in 2003. These activities stimulated global interest and generated concern about the potential conservation implications. The IUCN Global Plan of Action for the Conservation of Cetaceans had stated that as a general principle, small cetaceans should not be captured or removed from a wild population unless that specific population has been assessed and shown capable of sustaining the removals.
A principal goal of the Soma workshop was to elaborate on the elements of an assessment that would meet this standard. Participants noted that an assessment involving delineation of stock boundaries, abundance, reproductive potential, mortality and trend cannot necessarily be achieved quickly or inexpensively.
Specific topics covered by the workshop included management goals and assessment options, general biology and life history of bottlenose dolphins, forms of direct removal of dolphins from the wild, other threat factors, defining units to conserve, methods for estimating population size and assessment algorithms (e.g. population viability analysis). A framework for assessment was outlined, suggestions for genetic sampling and analyses were developed, and cultural and other local considerations for researchers working in the Pacific Islands region were summarised.
There is a need to determine the conservation status of Indo-Pacific bottlenose dolphin populations around islands where human-caused mortality or removal (direct or incidental catch) is known to be occurring. The species has a limited coastal range throughout much of the Indo-Pacific Ocean except in areas with wide continental shelves. Its near-shore distribution makes it particularly vulnerable to exploitation and other anthropogenic threats. In some regions where these dolphins have been studied, the populations have been found to be small compared to nearby open-ocean populations of common bottlenose dolphins (T. truncatus) and other species. The only known large concentrations (> ca. 1,000) are in regions with large shallow-water areas, e.g. Shark Bay on the western coast of Australia, North Stradbroke Island on the eastern coast of Australia and the Arabian Gulf. Given the restricted areas of potentially suitable habitat, populations of T. aduncus in the South Pacific islands are likely small, i.e. in the hundreds.
The government of the Solomon Islands had issued a permit for export of up to 80 dolphins per year and it was reported at the workshop that the annual allowable export level was being increased to 100 dolphins of any species, but most likely to be only T. aduncus. If an international standard rule allowing 1% or 2% of a population to be removed annually (per IWC, ASCOBANS etc.) were applied in this instance, the local T. aduncus population would have to be at least 5,000 or 10,000 to sustain the permitted level of exports. Based on the current state of knowledge of Indo-Pacific bottlenose dolphins throughout their range, as well as the information on this species in the Solomon Islands reviewed at the workshop, abundance in the area of recent live-captures appears to be well below 5,000. By the time of the workshop, an ongoing photo-identification study around Guadalcanal Island had catalogued only somewhat more than 100 individuals. Population assessment efforts need to be expanded if live-capture activities are to continue. It was concluded that the best approach to assess abundance and delineate populations would be a combination of mark-recapture analyses of photo-identification data and genetic analyses of tissue samples. It is assumed that Indo-Pacific bottlenose dolphins are not taken in the drive hunt in the Solomon Islands, but if they are, then both types of removal – live-capture and hunting – would need to be considered in any assessment of population status.
For more details on the workshop the report is available for download
News items related to this topic:
Mar 2013 – Assessment of the sustainability of Solomon Islands live dolphin captures
June 2011 – Solomon Islands dolphin project: Progress report