Residency and abundance of sperm whales (Physeter macrocephalus) in the Bleik Canyon, Norway

Abstract

Sperm whales (Physeter macrocephalus) are widely distributed in the Norwegian Sea and feeding aggregations occur. One of these aggregations is in the Bleik Canyon, close to shore in Norway, where the present study was performed. The study used a whale safari company as a platform from which to conduct a photo-identification study of male sperm whales. Data for this study was comprised of a total of 3856 images from 22 seasons (1987–2010) of whale-watching tours. In total, 411 individuals were identified. This study supports the results from previous photo-identification studies in the Bleik Canyon and confirms the presence of both transient and resident male sperm whales in the Bleik Canyon. These results suggest that the sperm whale group(s) found there are a loose feeding aggregation and not a closed population. Total residence time varied between one day and 14 years, although most individuals were only seen in one or two years. The number of sighted whales fluctuated between years, from eight to 77 individuals. No trend in the number of sighted whales was found. The estimated size of the feeding aggregation in the Bleik Canyon also fluctuated between years, from 11 to 116 individuals, with no trend evident.

Key words:

• Bleik Canyon
• feeding aggregations
• mark–recapture estimation
• sperm whales

Acknowledgements

Thanks to all the researchers from previous years back to 1987 for their efforts, skills and devoted work in providing photo-identification images for this study: Morten Lindhardt, Hanne Strager, Erland Lettevall, Daniele Zanoni, Tuula Skarstein, Vivi Fleming, Luca Lamoni, Marta Acosta, Camilla Ilmoni, Montserrat Domingo, Lara Polo, Luca Tassara. Thanks to Erland Lettevall for being a good consultant during the study, and to Tore Schweder and Karl Ugland from the University of Oslo for much help with statistics and modelling. Thanks to Stein Fredriksen, University of Oslo, for all his help during the study.

Disclosure statement

No potential conflict of interest was reported by the authors.

Funding

This work was supported by the Whale Safari Andenes Research Department (Norway) and the Institute of Marine Research (Norway).

Editorial responsibility: Rus Hoelzel