Cristin-resultat-ID: 1959999
Sist endret: 28. februar 2022, 10:28
NVI-rapporteringsår: 2021
Vitenskapelig artikkel

Killer whale (Orcinus orca) population dynamics in response to a period of rapid ecosystem change in the eastern North Atlantic

  • Eve Marie Jourdain
  • Tiffany Goh
  • Sanna Kuningas
  • Tiu Similä
  • Dag Vongraven
  • Richard Karoliussen
  • mfl.


Ecology and Evolution
ISSN 2045-7758
e-ISSN 2045-7758
NVI-nivå 1

Om resultatet

Vitenskapelig artikkel
Publiseringsår: 2021
Volum: 11
Sider: 17289 - 17306
Open Access


Scopus-ID: 2-s2.0-85119200351



Marinbiologi • Økologi

Beskrivelse Beskrivelse


Killer whale (Orcinus orca) population dynamics in response to a period of rapid ecosystem change in the eastern North Atlantic


This study investigates survival and abundance of killer whales (Orcinus orca) in Norway in 1988–2019 using capture–recapture models of photo-identification data. We merged two datasets collected in a restricted fjord system in 1988–2008 (Period 1) with a third, collected after their preferred herring prey shifted its wintering grounds to more exposed coastal waters in 2012–2019 (Period 2), and investigated any differences between these two periods. The resulting dataset, spanning 32 years, comprised 3284 captures of 1236 whales, including 148 individuals seen in both periods. The best-supported models of survival included the effects of sex and time period, and the presence of transients (whales seen only once). Period 2 had a much larger percentage of transients compared to Period 1 (mean = 30% vs. 5%) and the identification of two groups of whales with different residency patterns revealed heterogeneity in recapture probabilities. This caused estimates of survival rates to be biased downward (females: 0.955 ± 0.027 SE, males: 0.864 ± 0.038 SE) compared to Period 1 (females: 0.998 ± 0.002 SE, males: 0.985 ± 0.009 SE). Accounting for this heterogeneity resulted in estimates of apparent survival close to unity for regularly seen whales in Period 2. A robust design model for Period 2 further supported random temporary emigration at an estimated annual probability of 0.148 (± 0.095 SE). This same model estimated a peak in annual abundance in 2015 at 1061 individuals (95% CI 999–1127), compared to a maximum of 731 (95% CI 505–1059) previously estimated in Period 1, and dropped to 513 (95% CI 488–540) in 2018. Our results indicate variations in the proportion of killer whales present of an undefined population (or populations) in a larger geographical region. Killer whales have adjusted their distribution to shifts in key prey resources, indicating potential to adapt to rapidly changing marine ecosystems.


Eve Marie Jourdain

  • Tilknyttet:
    ved Akvatisk biologi og toksikologi ved Universitetet i Oslo
  • Tilknyttet:
    ved Andre institusjoner

Tiffany Goh

  • Tilknyttet:
    ved University of St Andrews

Sanna Kuningas

  • Tilknyttet:
    ved Luonnonvarakeskus

Tiu Similä

  • Tilknyttet:
    ved Andre institusjoner

Dag Vongraven

  • Tilknyttet:
    ved Norsk Polarinstitutt
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