The following encounter summary statistics are derived from the Whale Sighting Sheet data (2003-2008) and are reported in: Birtles, A., Valentine, P., Curnock, M., Mangott, A. Sobtzick, S., & Marsh, H. (2010). Dwarf Minke Whale Tourism Monitoring Program (2003-2008): Final Report to the Great Barrier Reef Marine Park Authority, 21 June 2010, 117pp.
An ‘encounter’ with dwarf minke whales is defined as a sighting of and/or interaction with one or more whales, beginning at the time of first sighting (by any person on the vessel or in the water nearby) and ending at the time a whale is last sighted, which may occur as the vessel departs the area or when whales leave the area. An ‘in-water interaction’ occurs when one or more dwarf minke whales are observed by a person or people in the water (who are likely to be using either snorkel equipment or SCUBA). Thus all in-water interactions are encounters, however not all encounters will result in an in-water interaction.
Seasonality of minke whale encounters in the GBR
90% of dwarf minke whale encounters in the Great Barrier Reef (GBR) occur in June & July. As shown in Figure 1 (below), the number of encounters ‘peaks’ in late June and early July.
Number of whales per encounter
The number of whales reported in dwarf minke whale encounters has ranged from 1 to >25 animals (estimated). Most commonly, a single whale is encouncountered. The mean number of whales per encounter over 2003-2008 was 2.9 whales (median = 2). This figure varies significantly between different locations within the GBR. It is important to note that the number of whales reported for many encounters are estimates. Identifying the number of whales involved in an encounter can be difficult when more whales are present and in rough weather conditions.
Duration of encounters
The mean duration of encounters with dwarf minke whales in the GBR (over six seasons, 2003-2008) is 84 minutes (range from 1 minute to >11 hours). The mean duration of minke whale encounters also varies between different locations within the GBR Marine Park.
Location of encounters
The majority of dwarf minke whale encounters reported in the GBR Marine Park are in the Ribbon and Agincourt Reef complexes. More than 70% of these encounters occurred at specific dive sites, where the vessel was either tied to a fixed mooring or was at anchor. Figure 1 below shows the location of minke whale encounters over 2006-2008. Figure taken from: Curnock, M.I. (2010). Mechanisms for assessing the sustainability of swimming-with-whales tourism in the Great Barrier Reef. PhD thesis, James Cook University.