Cetacean sightings off the Fiordland coastline: Analysis of commercial marine mammal viewing data 1996-99

From 1996 to 1999, 1422 sightings of cetaceans were recorded by observers on tour boats in the fiords and off the coast of Fiordland. These were compiled by the New Zealand Department of Conservation. Only 2.9% of the sightings were collected outside of Milford and Doubtful Sounds since most of the sampling effort was concentrated in these two fiords. In addition to species identification, group size and location were also recorded. Nine species were identified: bottlenose dolphin (Tursiops sp.), dusky dolphin (Lagenorhynchus obscurus), common dolphin (Delphinus sp.), long-finned pilot whale (Globicephala malaena edwardi), orca (Orcinus orca), humpback whale (Megaptera novaeangliae), southern right whale (Eubalaena australis), minke whale (Balaenoptera acutorostrata) and sperm whale (Physeter catodon). These are the first official records of long-finned pilot whale and minke whale in the region. Bottlenose dolphins were the most commonly observed species in all areas (87.8% of all sightings), followed by dusky dophins (10.3%). Along the coastline outside the fiords, bottlenose dolphins were also the predominant species (48.1% of sightings, n = 27), followed again by dusky dolphin (33.3%). Observations from this sighting network were compared with studies, which used standard sampling techniques, undertaken in the area. Spatial and temporal variations in tour operator sightings were accurate and reliabce. Estimates of dolphin group size were accurate up to 25 individuals. If the group was larger than 25 animals, its size was overestimated by tour operators. Species distribution at a large scale (Fiordland coastline) and small scale (within Doubtful and Milford Sounds) is discussed. Temporal variations in distribution and group size were also assessed; observer bias was taken into consideration.