Movements, diving behaviour and diet of type‐C killer whales (<scp><i>Orcinus orca</i></scp>) in the Ross Sea, Antarctica

Lauriano, Giancarlo; Pirotta, Enrico; Joyce, Trevor; Pitman, Robert L.; Borrell, Asunción; Panigada, Simone

doi:10.1002/aqc.3371

Cited by 8 publications

(12 citation statements)

References 56 publications

(130 reference statements)

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“…While Parker et al (2016) called for continued monitoring of toothfish along the lines of the DeVries dataset (see also the proposal in Ashford et al 2017), their study in 2014 proved to be a single-year effort. On the basis of increasing evidence supporting the importance of toothfish to Weddell seals (as well as killer whales; Lauriano et al 2020), we agree with Parker et al (2016) that CCAMLR, through the CEMP, should be moving towards a serious effort to monitor the ‘ecological relationships between harvested, dependent and related populations’ (quote from CCAMLR Article II) with respect to the Ross Sea Antarctic toothfish fishery and Weddell seals. Given the presence of intraguild predation in the toothfish food web (including seals, killer whales and silverfish), continued fishing of toothfish towards the 50% reduction management objective, without further research on the seal-toothfish relationship, has the potential to produce unexpected and unintended effects.…”

Section: Discussionsupporting

confidence: 78%

“…Our evidence, in addition to that offered in other studies (e.g. Testa et al 1985, Salas et al 2017, Lauriano et al 2020), confirms that toothfish are being preyed upon by Weddell seals Leptonychotes weddellii Lesson and other predators in appreciable numbers, contrary to CCAMLR's supposition. Our finding indicates that toothfish may indeed be ecologically important prey, especially for the Weddell seal, an iconic, endemic and key component of the high-latitude Southern Ocean (Fig.…”

Section: Introductionsupporting

confidence: 74%

“…Further extending this intraguild food web scenario, killer whales Orcinus orca L. prey on both the toothfish and the seal, as well as perhaps the silverfish (Fig. 5) (reviewed in Pitman et al 2018, and also Lauriano et al 2020).

Fig.…”

Section: Antarctic Toothfishmentioning

confidence: 95%

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Further evidence that Antarctic toothfish are important to Weddell seals

et al. 2020

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Antarctic toothfish Dissostichus mawsoni and Weddell seals Leptonychotes weddellii are important mesopredators in the waters of the Antarctic continental shelf. They compete with each other for prey, yet the seals also prey upon toothfish. Such intraguild predation means that prevalence and respective demographic rates may be negatively correlated, but quantification is lacking. Following a review of their natural histories, we initiate an approach to address this deficiency by analysing scientific fishing catch per unit effort (CPUE; 1975–2011 plus sporadic effort to 2018) in conjunction with an annual index of seal abundance in McMurdo Sound, Ross Sea. We correlated annual variation in scientific CPUE to seal numbers over a 43 year period (1975–2018), complementing an earlier study in the same locality showing CPUE to be negatively correlated with spatial proximity to abundant seals. The observed relationship (more seals with lower CPUE, while controlling for annual trends in each) indicates the importance of toothfish as a dietary item to Weddell seals and highlights the probable importance of intra- and inter-specific competition as well as intraguild predation in seal-toothfish dynamics. Ultimately, it may be necessary to supplement fishery management with targeted ecosystem monitoring to prevent the fishery from having adverse effects on dependent species.

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Section: Discussionsupporting

confidence: 78%

Section: Introductionsupporting

confidence: 74%

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Further evidence that Antarctic toothfish are important to Weddell seals

et al. 2020

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“…These seals did not concentrate in polynyas, but instead those individuals that made excursions beyond the core areas moved into areas of relatively high ice concentrations (80% plus). Inhabiting high sea-ice concentration areas may improve access to prey or reduce the risk of attack by predators such as killer whales (Lauriano et al, 2020). Similarly, sedentary individuals remaining in the fast ice may reduce predation risk.…”

Section: Individual Variabilitymentioning

confidence: 99%

Regional Variation in Winter Foraging Strategies by Weddell Seals in Eastern Antarctica and the Ross Sea

et al. 2021

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The relative importance of intrinsic and extrinsic determinants of animal foraging is often difficult to quantify. The most southerly breeding mammal, the Weddell seal, remains in the Antarctic pack-ice year-round. We compared Weddell seals tagged at three geographically and hydrographically distinct locations in East Antarctica (Prydz Bay, Terre Adélie, and the Ross Sea) to quantify the role of individual variability and habitat structure in winter foraging behaviour. Most Weddell seals remained in relatively small areas close to the coast throughout the winter, but some dispersed widely. Individual utilisation distributions (UDi, a measure of the total area used by an individual seal) ranged from 125 to 20,825 km2. This variability was not due to size or sex but may be due to other intrinsic states for example reproductive condition or personality. The type of foraging (benthic vs. pelagic) varied from 56.6 ± 14.9% benthic dives in Prydz Bay through 42.1 ± 9.4% Terre Adélie to only 25.1 ± 8.7% in the Ross Sea reflecting regional hydrographic structure. The probability of benthic diving was less likely the deeper the ocean. Ocean topography was also influential at the population level; seals from Terre Adélie, with its relatively narrow continental shelf, had a core (50%) UD of only 200 km2, considerably smaller than the Ross Sea (1650 km2) and Prydz Bay (1700 km2). Sea ice concentration had little influence on the time the seals spent in shallow coastal waters, but in deeper offshore water they used areas of higher ice concentration. Marine Protected Areas (MPAs) in the Ross Sea encompass all the observed Weddell seal habitat, and future MPAs that include the Antarctic continental shelf are likely to effectively protect key Weddell seal habitat.

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“…The RSKW is distributed in the coastal area, where it is known to search for prey, mainly consisting of fish (Krahn et al, 2008;Lauriano et al, 2020). Occurrence and movements of the RSKW are described for the Mc Murdo Sound area (Ainley et al, 2017;Pitman et al, 2018), where the ecotype is known to occur in mid-November to benefit from prey availability in the icebreaker channel to catch the Antarctic toothfish (Dissostichus mawsoni).…”

Section: Introductionmentioning

confidence: 99%

Ecotoxicological Characterization of Type C Killer Whales From Terra Nova Bay (Ross Sea, Antarctica): Molecular Biomarkers, Legacy, and Emerging Persistent Organic Contaminants

et al. 2022

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Among killer whale forms, type C is a fish-eating form and is the most common in the Ross Sea. In the austral summer 2015, a study was conducted to evaluate the toxicological hazard these marine mammals face in the Antarctic ecosystem. Seven biopsy samples were collected from adult individuals (five males and two females) in the surroundings of the Italian Research Station Mario Zucchelli, Terra Nova Bay, by remote dart sampling from the pack ice. The accumulation levels of persistent organic pollutants (POPs) such as legacy (DDTs, PCBs, and HCB) and emerging (PBDEs and DP) were measured. Moreover, the protein expression of cytochrome P450 (CYP1A1 and 2B) and the mRNA level variations of the peroxisome proliferator-activated receptors α and γ (PPARα-γ) and the estrogen receptor α (ERα), aryl hydrocarbon receptor (AhR), and Cyp1a were evaluated. Twenty PCB congeners, six DDTs, HCB, three HCHs, and fourteen brominated BDEs and DP-syn and anti-isomers were analyzed on freeze-dried blubber biopsy samples by GC-MS. The protein expression was evaluated by Western Blot and the mRNA levels were quantified by quantitative real-time PCR. The average abundance pattern for the contaminants was DDTs > PCBs > HCB > HCHs ≈ PBDEs >> DP. Contaminant levels resulted to be lower when compared to the existing data from the Antarctic type C killer whales from the McMurdo Sound (Ross Sea) and those reported for fish-eating killer whales worldwide. The mRNA levels of the five target genes were successfully quantified, but no statistical correlation was found with POP levels, suggesting that either the low levels of quantified POPs in blubber may not significantly affect the biological responses investigated, or that other stressors could contribute to the alterations of the molecular biomarkers. Although the results showed a lower risk related to contamination compared to more impacted areas, this study provides baseline data for the conservation of this species in an area with high ecological value, recently declared as the largest Marine Protected Area in Antarctica, where pollutants should remain at minimum levels despite increasing multiple stresses existing in the region.

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Movements, diving behaviour and diet of type‐C killer whales (Orcinus orca) in the Ross Sea, Antarctica

Cited by 8 publications

References 56 publications

Further evidence that Antarctic toothfish are important to Weddell seals

Further evidence that Antarctic toothfish are important to Weddell seals

Regional Variation in Winter Foraging Strategies by Weddell Seals in Eastern Antarctica and the Ross Sea

Ecotoxicological Characterization of Type C Killer Whales From Terra Nova Bay (Ross Sea, Antarctica): Molecular Biomarkers, Legacy, and Emerging Persistent Organic Contaminants

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