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

Jourdain, Eve; Goh, Tiffany; Kuningas, Sanna; Similä, Tiu; Vongraven, Dag; Karoliussen, Richard; Bisther, Anna; Hammond, Philip S.

doi:10.1002/ece3.8364

Cited by 5 publications

(7 citation statements)

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“…Because tags were deployed during carousel feeding (see Materials and Methods), our results likely underestimate the importance of seiner feeding for killer whales at herring wintering grounds. Of note, fishing activity at herring wintering grounds typically starts after twilight (Jourdain et al, 2021) when the herring ascend to the upper water column (Røttingen et al, 1994). Therefore, it cannot be ruled out that no detection of carousel feeding during the hours of darkness is caused by killer whales preferentially scavenging around fishing vessels as the vessels become active, rather than killer whales not carousel feeding at night at all.…”

Section: Discussionmentioning

confidence: 99%

“…Long term photo identification studies conducted between 1986 and 2003 at former herring wintering grounds estimated a minimum of 700 killer whales to be foraging and feeding on NSS herring, at least seasonally (Kuningas et al, 2014). More recent work has led to an updated estimate of around 1,900 killer whales at dynamic herring wintering grounds between 2012 and 2019 (Jourdain et al, 2021). Being one of the largest fish stocks worldwide, the NSS herring has been shown to play key roles in the marine ecosystems of the Norwegian and the Barents Seas and is also of major economic importance (Varpe et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

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Feeding characteristics and prey profitability in five herring‐feeding killer whales (Orcinus orca) in northern Norway

Matika

Jourdain²,

Cade

et al. 2022

Marine Mammal Science

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This study used multisensory data tags with integrated 4K video to investigate feeding behavior and prey profitability in five adult male killer whales (Orcinus orca) at herring wintering grounds in Norway, in 2016 and 2017. Video recorded two killer whales engaged in carousel feeding, and two engaged in seiner feeding (i.e., feeding on herring discards around purse seiner vessels). The feeding behaviors identified from the video data allowed for determination of associated kinematic signatures, which were used to further identify and characterize carousel feeding and deep feeding dives over the entire logger duration. Prey consumption during on camera feeding bouts was also measured to calculate profitability of feeding bouts for the different behaviors. Average number of prey consumed per minute was 1.08 ± 0.43 for carousel feeding and 0.43 ± 0.07 for seiner feeding (n = 122 prey capture events). Using kinematic data, a total of 18 carousel feeding bouts and 206 deep feeding dives were identified. Whales spent at least 37%-65% of time over 24 hr feeding. Using field metabolic rate estimates from the literature and the energetic content of herring caught locally, killer whales required an estimated 285-578 herring/day to balance daily energy requirements.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Feeding characteristics and prey profitability in five herring‐feeding killer whales (Orcinus orca) in northern Norway

Matika

Jourdain²,

Cade

et al. 2022

Marine Mammal Science

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“…Data on diet and social affiliations of photo-identified killer whales have been collected across all seasons in Norway. Most individuals were encountered at herring wintering grounds, consistent with herring being an important seasonal prey resource [ 28 ]. After the herring departed the wintering grounds, a subset of known herring-eating killer whales was annually observed to switch to feeding on other fish prey (e.g.…”

Section: Methodsmentioning

confidence: 99%

“…Photographs were scored for quality, and individuals' sex ( female, male, unknown) was determined based on observational evidence of physical and sexual maturity following the methods described in [28]. Photo-identified killer whales were assigned a dietary group based on a decade of individuals' predation records, seasonal occurrence patterns and skin stable isotopic values (for details, see electronic supplementary material; [22][23][24]28]).…”

Section: (C) Photo-identification and Attributes Of Individualsmentioning

confidence: 99%

Social and genetic connectivity despite ecological variation in a killer whale network

Jourdain,

Karoliussen,

Fordyce Martin

et al. 2024

Proc. R. Soc. B.

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Philopatric kin-based societies encourage a narrow breadth of conservative behaviours owing to individuals primarily learning from close kin, promoting behavioural homogeneity. However, weaker social ties beyond kin, and across a behaviourally diverse social landscape, could be sufficient to induce variation and a greater ecological niche breadth. We investigated a network of 457 photo-identified killer whales from Norway (548 encounters in 2008–2021) with diet data available (46 mixed-diet individuals feeding on both fish and mammals, and 411 exclusive fish-eaters) to quantify patterns of association within and between diet groups, and to identify underlying correlates. We genotyped a subset of 106 whales to assess patterns of genetic differentiation. Our results suggested kinship as main driver of social bonds within and among cohesive social units, while diet was most likely a consequence reflective of cultural diffusion, rather than a driver. Flexible associations within and between ecologically diverse social units led to a highly connected network, reducing social and genetic differentiation between diet groups. Our study points to a role of social connectivity, in combination with individual behavioural variation, in influencing population ecology in killer whales.

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“…Investigation of how these rates have varied over time may also provide insight into the influence of environmental changes (e.g. Agrelo et al 2021;Jourdain et al 2021). Incorporating population-specific birth and survival rates in population dynamics models, such as a population viability analysis, allows population growth rates to be estimated and inferences made about future conservation action that may be needed to halt a decline in abundance (e.g.…”

Section: Introductionmentioning

confidence: 99%

Investigating local population dynamics of bottlenose dolphins in the northern Bahamas and the impact of hurricanes on survival

et al. 2022

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Little Bahama Bank in the northern Bahamas supports several populations of bottlenose dolphins (Tursiops truncatus). We provide the first estimates of birth rate and age-class-specific apparent survival rates for the local South Abaco population using data from a long-term (1997–2014) photo-identification (photo-ID) study and use the estimated life history parameters in a population viability analysis (PVA) to predict future population trends. Hurricane events are predicted to become more intense due to climate change but knowledge of how hurricanes may impact cetacean populations is limited. Little Bahama Bank is subject to hurricane activity, so we also investigate the potential impact of hurricanes on calf, juvenile and adult survival. Photo-ID data confirmed the existence of a core adult population with relatively high site fidelity in South Abaco, but also evidence of transient animals. Estimated annual birth rate was 0.278 (95% CI: 0.241–0.337). We found strong support for a decline in apparent survival for all age-classes. Estimated survival declined by 9% in adults (0.941 in 1998, to 0.855 in 2013), 5% in juveniles (0.820 in 2000, to 0.767 in 2013) and 36% in calves (0.970 in 1997, to 0.606 in 2013). Evidence that survival was influenced by repeated hurricane activity leading to increased mortality and/or emigration was stronger for calves and juveniles than for adults. PVA simulations of an assumed isolated South Abaco population showed that declines would lead to extinction within decades, even under the most optimistic scenario. Future work should focus on establishing if South Abaco is part of natural source–sink metapopulation dynamics on Little Bahama Bank by assessing trends in abundance in local populations and establishing how they interact; this will be important for assessing their conservation status in a potentially increasingly changing environment.

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

Abstract: This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cited by 5 publications

References 70 publications

Feeding characteristics and prey profitability in five herring‐feeding killer whales (Orcinus orca) in northern Norway

Feeding characteristics and prey profitability in five herring‐feeding killer whales (Orcinus orca) in northern Norway

Social and genetic connectivity despite ecological variation in a killer whale network

Investigating local population dynamics of bottlenose dolphins in the northern Bahamas and the impact of hurricanes on survival

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