Long term monitoring of two of Fiordland’s bottlenose dolphin populations in Doubtful Sound, and Dusky/Breaksea Sounds reveal that both populations are slowly increasing. A team from DOC Te Anau and Otago University run three monitoring trips per area every year, with the trips being timed around the start and end of the calving period in spring/summer, and a winter trip to assess survival over the colder months.
The trips are aimed at assessing abundance, adult and calf survival and mortality, and long term distribution patterns using a non-invasive technique known as photo identification. A dolphin’s dorsal fin is as unique as a human fingerprint, collecting scars and notches from social interactions over the course of their lifetime. Photo identification aims to get a good photo from a 90° angle, which can then be compared against a catalogue, and changes in individual markings can be tracked over time.
There are currently 71 individuals in the Doubtful Sound bottlenose dolphin population. This is the second highest recorded abundance since monitoring began in the early 1990’s; the highest recorded abundance for this population was 75 in 1995/96.
Three out of the four calves born over the summer of 2013/14 are still alive, with no sightings at present of new calves for this summer period. In July 2014, seven adults from the Doubtful Sound population were sighted in Dusky Sound not far from a pod of resident Dusky Sound bottlenose dolphins. This is the first confirmed sighting of resident Doubtful Sound dolphins in Dusky Sound since 2003.
The resident bottlenose dolphin population in Dusky Sound now numbers a record high of 131 individuals since monitoring began in 2007. The population increase is due mostly to the 2013/14 breeding season, which saw a record number of 14 calves born in one summer. At least 11 of the 14 calves survived through the winter. The most recent monitoring trip in October recorded three new calves for the current summer season.
Chloe Corne, DOC Te Anau