Prey selection of offshore killer whales Orcinus orca in the Northeast Atlantic in late summer: spatial associations with mackerel

Nøttestad, Leif; Sivle, Lise Doksæter; Krafft, Bjørn A.; Langård, Lise; Anthonypillai, Valantine; Bernasconi, Matteo; Langøy, Herdis; Fernö, Anders

doi:10.3354/meps10638

Cited by 30 publications

(35 citation statements)

References 41 publications

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“…Killer whales were associated with NEA mackerel, which is in line with results also found in the same area during 2006/2007 (Nøttestad et al, 2014b). Mean group size of killer whales was between 5.1 and 9.2 animals from 2009 to 2012, which is comparable with mean group size = 8.2 animals found in the Norwegian Sea in summers 2006 and 2007 (Nøttestad et al, 2014b).…”

Section: Discussionsupporting

confidence: 79%

“…This was in contrast to the earlier perception that their main prey was the Norwegian spring-spawning (NSS) herring (Clupea harengus) (Sigurjónsson et al, 1988;Similä et al, 1996;Simon et al, 2006). This has been the case at least for the more coastal areas, but no such focused large scale study prior to Nøttestad et al (2014b) had given attention to the offshore areas of this highly productive marine ecosystem. Furthermore, the collective behavior of killer whales have been found fine-tuned to prey schooling size and behavior (Nøttestad et al, 2002(Nøttestad et al, , 2014b.…”

Section: Introductioncontrasting

confidence: 48%

“…Despite ascertainable changes in the whale prey communities in the Norwegian Sea, no clear changes in fin-(Balaenoptera physalus) or humpback whale (Megaptera novaengliae) distribution patterns were detected in a study investigating sighting data collected during (Nøttestad et al, 2014a), compared to distributional trends reported 10-15 years earlier Vikingsson et al, 2009). A recent study on offshore-feeding killer whales (Orcinus orca) in this system found that they mainly targeted northeast Atlantic mackerel (Scomber scombrus) (Nøttestad et al, 2014b). This was in contrast to the earlier perception that their main prey was the Norwegian spring-spawning (NSS) herring (Clupea harengus) (Sigurjónsson et al, 1988;Similä et al, 1996;Simon et al, 2006).…”

Section: Introductionmentioning

confidence: 93%

“…This has been the case at least for the more coastal areas, but no such focused large scale study prior to Nøttestad et al (2014b) had given attention to the offshore areas of this highly productive marine ecosystem. Furthermore, the collective behavior of killer whales have been found fine-tuned to prey schooling size and behavior (Nøttestad et al, 2002(Nøttestad et al, , 2014b.…”

Section: Introductionmentioning

confidence: 99%

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Recent changes in distribution and relative abundance of cetaceans in the Norwegian Sea and their relationship with potential prey

et al. 2015

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This study aimed to assess possible shifts in distributional patterns of cetaceans residing in the Norwegian Sea, and to relate the distribution to their feeding ecology during the summer seasons of 2009, 2010, and 2012. During this same period, historically large abundances in the order of 15 million tonnes pelagic planktivorous fish such as Norwegian spring-spawning herring (Clupea harengus), northeast Atlantic mackerel (Scomber scombrus) and blue whiting (Micromesistius poutassou), have been reported feeding in the Norwegian Sea during the summer. There is also observed elevated average surface temperatures and a reduction in zooplankton biomass during the last two decades. Such changes might influence species composition, distribution patterns and feeding preferences of cetaceans residing the region. Our results show higher densities of toothed whales, killer whales (Orcinus orca) and pilot whales (Globicephala melas), than the previous norm for these waters. Baleen whales, such as minke whales (Balaenoptera acutorostrata) and fin whales (Balaenoptera physalus), which are often associated with macro-zooplankton, displayed a distribution overlap with pelagic fish abundances. Humpback whales (Megaptera novaeangliae) were observed in low numbers, indicating a shift in habitat preference, compared to sighting data collected only few years earlier. Our study illustrate that both small and large cetaceans that reside in the Norwegian Sea have the capability to rapidly perform shifts in distribution and abundance patterns strongly associated with adaptive search behavior in relation to both changing levels of abundance in their prey and elevated sea-surface temperatures. This study provides new evidence on high ecological plasticity in response to changing predator-prey trophic relationships and elevated sea-surface temperatures.

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Section: Discussionsupporting

confidence: 79%

Section: Introductioncontrasting

confidence: 48%

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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Recent changes in distribution and relative abundance of cetaceans in the Norwegian Sea and their relationship with potential prey

et al. 2015

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“…Distribution estimates can be highly uncertain for species that live in a dynamic environment and have complex behaviour and life histories (Isojunno et al 2012). Although they can often be related to physical oceanographic features such as water depth, it is likely that prey abundance and movements are the most important factors in determining the occurrence and movements of cetaceans (Gaskin 1982, Evans 1987, Nøttestad et al 2014. Oceanographic features have therefore been widely used as proxies of ecological variables such as prey distribution, which is difficult to obtain or cannot be measured (Torres et al 2008).…”

Section: Discussionmentioning

confidence: 99%

Habitat preferences among three top predators inhabiting a degraded ecosystem, the Black Sea

Sánchez-Cabanes¹,

Nimak-Wood²,

Harris³

et al. 2017

Sci. Mar.

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Summary: This study investigated whether there is evidence of widespread niche partitioning based on environmental factors in the Black Sea and tested the hypothesis that physiographic factors may be employed as predictors. It addresses poorly researched areas with good habitat potential for the only three cetacean subspecies living in this area: the Black Sea short-beaked common dolphin (Delphinus delphis spp. ponticus), the Black Sea bottlenose dolphin (Tursiops truncatus spp. ponticus) and the Black Sea harbour porpoise (Phocoena phocoena spp. relicta). Generalized additive models (GAMs) were used to analyse data collected from multiple sources. In total, 745 sightings of the three species between 1998 and 2010 throughout the Black Sea were included. The analysis found depth and sea surface temperature to be the most important variables for separating the occurrence of the three species. Common dolphins occurred mainly in deep waters and in areas where the sea surface temperature was low, bottlenose dolphins were distributed primarily in shallower and warmer waters than common dolphins, and harbour porpoises were distributed in shallower waters with lower sea surface temperature than bottlenose dolphins. This study suggests strong niche segregation among the three cetacean species. The study is also the first contribution to the basic information of cetacean species distribution and habitat preferences in the Black Sea as a whole. Knowledge of the distribution of the three dolphin species in the study area is essential to establish conservation measures for these populations.Keywords: Black Sea; bottlenose dolphin; common dolphin; GAM; habitat preferences; harbour porpoise; niche segregation; spatial modelling. Preferencias de hábitat de tres superpredadores en el mar NegroResumen: El presente trabajo analiza si existen evidencias de partición de nicho en base a factores ecológicos básicos en el mar Negro, así como si dichos factores pueden ser empleados como predictores de distribución en zonas pobremente muestreadas con respecto a las tres especies de cetáceos que habitan el área: el delfín común del mar Negro (Delphinus delphis spp. ponticus), el delfín mular del mar Negro (Tursiops truncatus spp. ponticus) y la marsopa del mar Negro (Phocoena phocoena spp. relicta). Se usaron Modelos Aditivos Generalizados (GAMs) para analizar grupos de datos provenientes de múltiples fuentes. En total fueron incluidos 745 avistamientos de las tres especies entre los años 1998 y 2000. El análisis indica que las variables profundidad y temperatura superficial del mar fueron las más influyentes a la hora de segregar las especies espacialmente. La distribución del delfín común indicó una relación positiva con aguas más profundas y frías, mientras el delfín mular y la marsopa con aguas más superficiales y cálidas, tendiendo esta última a localizarse en aguas más frías con respecto al delfín mular. Este trabajo sugiere, por lo tanto, que existe una importante segregación de nicho entre las tres especies de cetáceos. Este análi...

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Isotopic niche differs between seal and fish‐eating killer whales (Orcinus orca) in northern Norway

Jourdain¹,

Andvik

Karoliussen³

et al. 2020

Ecology and Evolution

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Ecological diversity has been reported for killer whales (Orcinus orca) throughout the North Atlantic but patterns of prey specialization have remained poorly understood. We quantify interindividual dietary variations in killer whales (n = 38) sampled throughout the year in 2017–2018 in northern Norway using stable isotopic nitrogen (δ15N: 15N/14N) and carbon (δ13C: 13C/12C) ratios. A Gaussian mixture model assigned sampled individuals to three differentiated clusters, characterized by disparate nonoverlapping isotopic niches, that were consistent with predatory field observations: seal‐eaters, herring‐eaters, and lumpfish‐eaters. Seal‐eaters showed higher δ15N values (mean ± SD: 12.6 ± 0.3‰, range = 12.3–13.2‰, n = 10) compared to herring‐eaters (mean ± SD: 11.7 ± 0.2‰, range = 11.4–11.9‰, n = 19) and lumpfish‐eaters (mean ± SD: 11.6 ± 0.2‰, range = 11.3–11.9, n = 9). Elevated δ15N values for seal‐eaters, regardless of sampling season, confirmed feeding at high trophic levels throughout the year. However, a wide isotopic niche and low measured δ15N values in the seal‐eaters, compared to that of whales that would eat solely seals (δN‐measured = 12.6 vs. δN‐expected = 15.5), indicated a diverse diet that includes both fish and mammal prey. A narrow niche for killer whales sampled at herring and lumpfish seasonal grounds supported seasonal prey specialization reflective of local peaks in prey abundance for the two fish‐eating groups. Our results, thus, show differences in prey specialization within this killer whale population in Norway and that the episodic observations of killer whales feeding on prey other than fish are a consistent behavior, as reflected in different isotopic niches between seal and fish‐eating individuals.

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Prey selection of offshore killer whales Orcinus orca in the Northeast Atlantic in late summer: spatial associations with mackerel

Cited by 30 publications

References 41 publications

Recent changes in distribution and relative abundance of cetaceans in the Norwegian Sea and their relationship with potential prey

Recent changes in distribution and relative abundance of cetaceans in the Norwegian Sea and their relationship with potential prey

Habitat preferences among three top predators inhabiting a degraded ecosystem, the Black Sea

Isotopic niche differs between seal and fish‐eating killer whales (Orcinus orca) in northern Norway

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