Documentation of a New Zealand blue whale population based on multiple lines of evidence

Abstract

Species conservation depends on robust population assessment. Data on population abundance, distribution, and connectivity are critical for effective management, especially as baseline information for newly documented populations. We describe a pygmy blue whale Balaenoptera musculus brevicauda population in New Zealand waters with year-round presence that overlaps with industrial activities. This population was investigated using a multidisciplinary approach, including analysis of survey data, sighting records, acoustic data, identification photographs, and genetic samples. Blue whales were reported during every month of the year in the New Zealand Exclusive Economic Zone, with reports concentrated in the South Taranaki Bight (STB) region, where foraging behavior was frequently observed. Five hydrophones in the STB recorded the New Zealand blue whale call type on 99.7% of recording days (January to December 2016). A total of 151 individuals were photo-identified between 2004 and 2017. Nine individuals were resighted across multiple years. No matches were made to individuals identified in Australian or Antarctic waters. Mitochondrial DNA haplotype frequencies differed significantly between New Zealand (n = 53 individuals) and all other Southern Hemisphere blue whale populations, and haplotype diversity was significantly lower than all other populations. These results suggest a high degree of isolation of this New Zealand population. Using a closed capturerecapture population model, our conservative abundance estimate of blue whales in New Zealand is 718 (SD = 433, 95% CI = 279−1926). Our results fill critical knowledge gaps to improve management of blue whale populations in New Zealand and surrounding regions.

Modelling the spatial distribution of cetaceans in New Zealand waters

“…For example, Bryde's whale predicted occurrence was predominately constrained to the Hauraki Gulf due to the high number of sightings in this area (year‐round population of Bryde's whales that are the focus of a whale watch industry and research programmes), despite knowledge that these are also an offshore species in New Zealand and elsewhere (Constantine et al, ). Recent surveys (data not included in our models) highlight that the Kaikoura coast along the north east of the South Island also have high occurrences of blue whales (Barlow et al, ) although this is not apparent from the models presented here due to the low number of sightings available for this location in our study. With the inclusion of newly acquired data, or the inclusion of mechanistic relationships in the distribution models, prediction accuracy and usefulness is likely to improve.…”

“…Further work is currently underway to investigate these important issues. (Barlow et al, 2018) although this is not apparent from the models presented here due to the low number of sightings available for this location in our study. With the inclusion of newly acquired data, or the inclusion of mechanistic relationships in the distribution models, prediction accuracy and usefulness is likely to improve.…”

“…For the more coastal species such as Māui and bottlenose dolphins and Bryde's whales, sufficient nearshore prey is available for year‐round populations to persist (Carroll et al, ; Constantine, Iwata, Nieukirk, & Penry, ; Hartel, Constantine, & Torres, ; Miller, Lalas, Dawson, Ratz, & Slooten, ). Blue whales frequently aggregate in areas of nearshore upwelling that drive zooplankton productivity during the austral summer months from approximately January to April (Barlow et al, ; Torres, ).…”

“…For the more coastal species such as Māui and bottlenose dolphins and Bryde's whales, sufficient nearshore prey is available for year-round populations to persist (Carroll et al, 2019;Constantine, Iwata, Nieukirk, & Penry, 2018;Hartel, Constantine, & Torres, 2014;Miller, Lalas, Dawson, Ratz, & Slooten, 2013). Blue whales frequently aggregate in areas of nearshore upwelling that drive zooplankton productivity during the austral summer months from approximately January to April (Barlow et al, 2018;Torres, 2013 Miller et al, 2013). Southern right whales currently use the subantarctic Auckland Islands as a primary winter breeding ground, moving further south to feed (Childerhouse, Double, & Gales, 2010;Patenaude et al, 1998).…”

Estimating morphometric attributes of baleen whales with photogrammetry from small UASs: A case study with blue and gray whales

“…Small UAS overflights of blue whales occurred in the South Taranaki Bight region of New Zealand during January and February 2016 as part of a larger project to describe the ecology of this population (Torres 2013; BURNETT ET AL. : PHOTOGRAMMETRIC WHALE MORPHOLOGY Barlow et al 2018). Field methods are thoroughly documented in Torres et al (2017).…”