Population size, survival and reproductive rates of northern Norwegian killer whales ( Orcinus orca ) in 1986–2003

• Published in: Journal of the Marine Biological Association of the United Kingdom
• Main Authors: Kuningas, Sanna, Similä, Tiu, Hammond, Philip S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2013
• Subjects: Aquatic Science; Norway; Killer Whale; Northern Norway; Orca; Orcinus orca; Killer whale
• Online Access: http://dx.doi.org/10.1017/s0025315413000933; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0025315413000933

A long-term photo-identification study of killer whales ( Orcinus orca ) in northern Norway was initiated in 1986, when their prey the Norwegian spring-spawning herring ( Clupea harengus ) started to winter in a complex fjord system. The aim of this work was to estimate population size and apparent survival rates in this killer whale population using photo-identification and mark–recapture techniques with data collected during October–December 1986–2003. Total population size was estimated to be highest in 2003: 731 individuals (SE = 139, 95% CI = 505–1059) using a model taking heterogeneity of capture probabilities into account. Apparent survival of adult males and adult females was estimated using the Cormack–Jolly–Seber model as 0.971 (SE = 0.008) and 0.977 (SE = 0.009), respectively. Calving intervals ranged from 3 to 14 years (mean = 5.06, SE = 0.722). These are the first estimates of northern Norwegian killer whale population parameters, allowing their dynamics to be investigated and comparisons to be made with killer whale populations globally.