ESR 36:27-40 (2018) - DOI: https://doi.org/10.3354/esr00891

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

Dawn R. Barlow1, Leigh G. Torres1,*, Kristin B. Hodge2, Debbie Steel1, C. Scott Baker1,3, Todd E. Chandler1, Nadine Bott4, Rochelle Constantine3, Michael C. Double5, Peter Gill6, Debra Glasgow7, Rebecca M. Hamner1,8, Callum Lilley4, Mike Ogle4, Paula A. Olson5,9, Catherine Peters10, Karen A. Stockin10, Christopher T. Tessaglia-Hymes2, Holger Klinck2

1Marine Mammal Institute, Department of Fisheries and Wildlife, Oregon State University, Newport, OR 97365, USA

2Bioacoustics Research Program, Cornell Lab of Ornithology, Cornell University, Ithaca, NY 14850, USA

3School of Biological Sciences, University of Auckland, Auckland 1142, New Zealand

4New Zealand Department of Conservation, Wellington 6143, New Zealand

5Australian Marine Mammal Centre, Australian Antarctic Division, Kingston, TAS 7050, Australia

6Blue Whale Study, Narrawong, VIC 3285, Australia

7PO Box 98, Paekakariki 5034, New Zealand

8Department of Life Sciences, Texas A&M University - Corpus Christi, Corpus Christi, TX 78412-5802, USA

9Southwest Fisheries Science Center NMFS/NOAA, La Jolla, CA 92037, USA

10Coastal-Marine Research Group, Institute of Natural and Mathematical Sciences, Massey University, Auckland 0745, New Zealand

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 capture-recapture 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.

KEY WORDS: Blue whale · New Zealand · Photo-identification · Abundance · Acoustics · Genetics · Population connectivity · Conservation