Figure 3. Cumulative number of bifurcations across AI levels for the data collected in nearshore Shetland and Eastern Icelandic waters. Significant knots that maximized Z statistics from comparisons of stepwise changes above and below the knot value and which signify social tier delineation were at an AI of 0.84 for Pacific and Scotland mammal-eating killer whales and, although non significant, at 0.86 for the Icelandic data. BECK Andy Foote/NAKID IMAGES RESULTS & DISCUSSION Both Atlantic killer whale groups had stable long-term primary social tiers (AI= 0.8). There were further bifurcations at a range of AIs in the Icelandic data, suggesting more frequent or more persistent associations at a secondary social tier. The mean and typical group size of Atlantic killer whales when hunting seals around the Scottish coast was 5 individuals, similar to the Pacific mammal-eating killer whales i,iii .The mean group size of Atlantic killer whales when hunting fish off Iceland was 15 individuals. The differences in sociality between Atlantic groups suggest that phylogenetic constraints may influence the formation of cohesive social groups at the primary social tier, however, the second social tier appears to be more plastic and influenced to some extent by ecological selection.

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.

Kuningas, S., Kvadsheim, P. H., Lam, F-P. A., and Miller, P. J. O. 2013. Killer whale presence in relation to naval sonar activity and prey abundance in northern Norway. – ICES Journal of Marine Science, 70: . In this study, retrospective data on naval sonar activity and prey abundance were correlated with killer whale sightings within a fjord basin in northern Norway. In addition, passive acoustic and visual marine mammal surveys were conducted before, during, and after a specific navy exercise in 2006. Herring abundance was the main factor affecting killer whale presence. Naval sonar, either operational navy sonar exercises (Flotex) or experimental sonar activity (CEE) alone, did not explain killer whale occurrence. However, naval sonar activity during a period of low prey availability seemed to have had a negative effect on killer whale presence. We conclude that the level of reaction to sonar can be influenced by multiple factors, including availability of prey.

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