Survey of Coastal Dolphin Species (Australian Snubfin (Orcaella heinsohni) and Indo-Pacific Humpback (Sousa chinensis)) in Kakadu National Park 

The dataset contains a record of coastal dolphin- Australian Snubfin (Orcaella heinsohni) and Indo-Pacific Humpback (Sousa chinensis)) species sighted, total number of individuals, and group/school size in Kakadu National Park rivers between March 2007 to August 2011. 

We at TERN acknowledge the Traditional Owners and Custodians throughout Australia, New Zealand and all nations. We honour their profound connections to land, water, biodiversity and culture and pay our respects to their Elders past, present and emerging. The project was undertaken jointly with the NT Department of Natural Resources, Environment, Arts and Sport (now the Department of Land Resource Management). 

Kakadu National Park (KNP), covering almost 20,000 square kilometres, is located 240 kilometres east of Darwin in Australia's tropical north. Coastal dolphins inhabit harbours, bays and estuaries and can be impacted by human activities in those areas. A boat-based survey was undertaken of two rare coastal dolphins in Kakadu National Park: the Australian Snubfin (Orcaella heinsohni) and Indo-Pacific Humpback (Sousa chinensis). The East and the South Alligator Rivers were surveyed between 2007-2011 and the West Alligator and Wildman Rivers were surveyed between 2010-2011. The objectives of the research were to record the distribution of these dolphin species, investigate habitat use, and determine important foraging areas. The project was undertaken as a collaboration between the NT Department of Natural Resources, Environment, the Arts and Sport and Kakadu National Park. Surveys were undertaken on the estuarine sections of East, South and West Alligator Rivers and the Wildman River. 

Boat-based survey : A two-day, boat-based survey was undertaken each month, weather permitting. Type of boats used were 57m aluminium open or half-cab vessels. At least three people undertook each survey, one coxswain and two observers/data recorders. Sighting data was recorded both on transect and off transect (traveling to start of transects). Along transect lines the boat traveled at 15 to 20 km/hour, with an observer scanning from each side of the boat, until a dolphin or dolphin group was sighted. Once a dolphin school was spotted, the school was approached to within 10 to 15 m. Data on each group were recorded on a hand-held PDA using Cyber tracker software. A dolphin group was defined as all dolphins within a 100 m radius of any other dolphin that was involved in similar behavioural activities. Due to weather, tides and sea state conditions, exact transects traversed may have varied from month to month. All records on and off the transect were combined in the dataset. Data recorded included: species, location, number of sightings, total number of individuals, group/school sizes, and behaviour.