Pygmy blue whales seen on a 2018 survey, New Zealand

Study Extent

Northern coast of West Coast, South Island and South Taranaki Bight

Sampling

Visual surveys for blue whales were conducted from the M/V Star Keys operated by Western Workboats. A smaller six-meter vessel ‘Brig’ outfitted with a specialized bowsprit was housed on-board for tagging and biopsy operations. Due to the limited time available, survey effort was initially focused in the Taranaki region due to a previously described high density of blue whale sightings in the area (Torres 2013; Torres et al. 2017). The research team consisted of Kimberly Goetz (NIWA, voyage leader), Simon Childerhouse (Blue Planet Marine, tagger), Dave Paton (Blue Planet Marine, small boat driver), Mike Ogle (Department of Conservation, biopsy collector), and Krista Hupman (NIWA, photo-identification).

Method steps

1. All visual surveys were conducted on an outdoor platform located above the wheelhouse, approximately 7 m above the water. During each survey, the research team rotated between three positions (left observer, recorder, right observer) and alternated between searching with and without 7x 50 binoculars. Each observer spent an hour at each position (three hours on-effort) followed by two hours off-effort to minimize fatigue. A custom-built survey program was used to record all survey information which consisted of sighting (position, date, number of individuals, behavior) and weather data (Beaufort, swell, sun position, glare, horizon visibility). Additional aerial surveys were undertaken to provide wider search effort for the survey.
2. Upon sighting a suspected blue whale, the vessel was guided towards the whale for species confirmation. If conditions were suitable, the Brig was launched and the main vessel acted as a safety and support vessel. The boat driver approached the animal to within 5-10 m while the tagger attached a satellite tag (SPOT-303F with a 45-sec repetition rate, Wildlife Computers) using a compressed air powered deployment (ARTS system) and collected a biopsy sample using Paxarm biopsy system. A biopsy was only attempted after tag attachment or when conditions were not suitable for tagging.
3. Because there is often only one chance to get within 10 m of a blue whale, the tasks were prioritized as follows: 1) tag deployment, 2) biopsy sample, 3) photo-identification.
4. When collected, biopsy samples were split and either frozen or stored in 70% ethanol for the following analyses: 1) genetic composition (ethanol), 2) stable isotope analysis (frozen), 3) hormone analysis (frozen). If the size of the biopsy sample allowed, a small portion was stored in ethanol to be housed in the tissue archive maintained by the University of Auckland. Before, during, and after tagging and biopsy operations, attempts were made to take photos for photo-identification using high resolution digital SLR cameras. However, given the priority of operations and time constraints, obtaining photographs of both right and left sides of individual animals was not possible. All data were archived at the end of each day for later quality control and reconciliation.

northern West Coast, South Island and South Taranaki Bight, New Zealand