Commercial krill fishing within a foraging supergroup of fin whales in the Southern Ocean

Ryan, Conor; Santangelo, Maya; Stephenson, Brent M.; Branch, Trevor A.; Wilson, Earle A; Savoca, Matthew S.

doi:10.1002/ecy.4002

Cited by 8 publications

(4 citation statements)

References 20 publications

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“…Based on a ship-based survey in the waters around Elephant Island and the South Orkney Islands in 2016, Viquerat & Herr 13 estimated average minimum densities of 0.0268 ± 0.0183 and 0.0588 ± 0.0381 whales km 2 in the two areas respectively, with minimum abundance estimates of 528 ± 362 and 796 ± 516 fin whales. These recent estimates, despite representing relatively small areas, suggest that fin whales in the SW Atlantic have increased in numbers over recent decades, something that is also supported by the increasingly common occurrence of very large fin whale feeding aggregations whales in some regions of the Southern Ocean 14,15 . However, the rate of increase remains poorly quantified 6 , and it is not known to what extent these geographically limited estimates reflect population trends over a larger spatial scale.…”

Section: Introductionmentioning

confidence: 82%

Estimated summer abundance and krill consumption of fin whales throughout the Scotia Sea during the 2018/2019 summer season

Biuw,

Lindstrøm,

Jackson

et al. 2024

Preprint

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Among large cetaceans in the Southern Hemisphere, fin whales were the most heavily exploited in terms of numbers taken during the period of intense industrial whaling. Recent studies suggest that, whilst some humpback whale populations in the Southern Hemisphere appears to have almost completely recovered to their estimated pre-whaling abundance, much less is known about the status of Southern Hemisphere fin whales. Circumpolar estimates in the 1990s suggest an abundance of about 5 500 animals south of 60° S, while the IDCR/SOWER-2000 survey for the Scotia Sea and Antarctic Peninsula areas estimated 4,670 fin whales within this region in 2000. More recent studies in smaller regions indicate higher densities, suggesting that previous estimates are overly conservative and/or that fin whales are undergoing a substantial increase. Here we report findings from a recent multi-vessel single-platform sightings survey carried out as part of the 2019 Area 48 Survey for Antarctic krill. While fin whales were encountered throughout the entire survey area, which covered the majority of CCAMLR Management Area 48, they were particularly abundant around the South Orkney Islands and the eastern Bransfield Strait. Large feeding aggregations were also encountered within the central Scotia Sea between South Orkney Islands and South Georgia. Distance sampling analyses suggest an average fin whale density throughout the Scotia Sea of 0.0256 (CV=0.149) whales per km2, which agrees well with recent density estimates reported from smaller sub-regions within the Scotia Sea. Design-based distance sampling analyses resulted in an estimated total fin whale abundance of 53,873 (CV=0.15, 95% CI: 40,233 - 72,138), while a density surface model resulted in a slightly lower estimate of 50,837 (CV: 0.136, 95% CI: 38,966 - 66,324). These estimates are at least an order of magnitude greater than the previous estimate from the same region based on the IDCR/SOWER-2000 data, suggesting that fin whales are undergoing a substantial abundance increase in the South Atlantic. This may have important implications for the assessment of cetacean population trends, but also for CCAMLRs spatial overlap analysis process and efforts to implement a Feedback Management system for Antarctic krill. Our abundance estimate suggests an annual summer krill consumption by fin whales in the Antarctic Peninsula and Scotia Sea area of 7.97 (95% CI: 4.94 - 11.91) million tonnes, which would represent around 20 times the total krill catch taken by the commercial fishery in Area 48 in the same season, or about 12.7% of the 2019 summer krill standing stock estimated from data collected during the same survey. This highlights the crucial importance of including cetacean krill predators in assessment and management efforts for living marine resources in the Southern Ocean, and particularly stresses the urgent need for a re-appraisal of abundance, distribution and ecological role of Southern Hemisphere fin whales.

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Section: Introductionmentioning

confidence: 82%

Estimated summer abundance and krill consumption of fin whales throughout the Scotia Sea during the 2018/2019 summer season

Biuw,

Lindstrøm,

Jackson

et al. 2024

Preprint

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“…Additionally, though we can observe inter-annual differences in the abundance and distribution of krill in restricted regions through the fisheries' catch data, little is known about the exact cause of krill biomass fluctuations and subsequently how such changes affect the marine mammals. The ability to predict inter-annual changes in regions within the Scotia Sea, which are characterized by ecosystem variability, is crucial due to the extensive overlap in resource exploitation between the commercial krill fishery and marine mammals [ 137 , 138 ], and especially due to future climate change.…”

Section: Discussionmentioning

confidence: 99%

Seasonal acoustic presence of marine mammals at the South Orkney Islands, Scotia Sea

Åsvestad,

Ahonen,

Menze

et al. 2024

R. Soc. open sci.

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Increased knowledge about marine mammal seasonal distribution and species assemblage from the South Orkney Islands waters is needed for the development of management regulations of the commercial fishery for Antarctic krill ( Euphausia superba ) in this region. Passive acoustic monitoring (PAM) data were collected during the autumn and winter seasons in two consecutive years (2016, 2017), which represented highly contrasting environmental conditions due to the 2016 El Niño event. We explored differences in seasonal patterns in marine mammal acoustic presence between the two years in context of environmental cues and climate variability. Acoustic signals from five baleen whale species, two pinniped species and odontocete species were detected and separated into guilds. Although species diversity remained stable over time, the ice-avoiding and ice-affiliated species dominated before and after the onset of winter, respectively, and thus demonstrating a shift in guild composition related to season. Herein, we provide novel information about local marine mammal species diversity, community structure and residency times in a krill hotspot. Our study also demonstrates the utility of PAM data and its usefulness in providing new insights into the marine mammal habitat use and responses to environmental conditions, which are essential knowledge for the future development of a sustainable fishery management in a changing ecosystem.

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“…In contrast, aggregations of baleen whales are more likely to occur when foraging (e.g. supergroups of fin whales Balaenoptera physalus 27 ) than when resting, probably facilitating the dispersal of nutrients ingested in nutrient hotspots. Small cetaceans, on the other hand, are commonly observed in groups both when foraging and when resting or socialising near the surface.…”

Section: Discussionmentioning

confidence: 99%

“… 18 – 21 ). Cetaceans are singular nutrient vectors in the oceans as (i) their waste products are greatly concentrated in nutrients compared to surface waters 7 , 8 , 22 , 23 , (ii) they are highly mobile, and can transfer nutrients against physical forces and between habitats of different nutrient regimes 24 , 25 , (iii) deep diving species can transfer nutrients from the ocean depths, where they feed, to the surface, mediating a nutrient pump known as the “whale pump” 7 , 26 , (iv) some species can form large aggregations and create “hotspots” and “hot moments” of nutrient biological cycling 24 , 27 , and, finally, (v) they are tied to the euphotic zone for breathing, where they release their wastes. On a large spatiotemporal scale, the gross nutrient enrichment caused by cetacean waste release is likely minor compared to that caused by physical processes (e.g.…”

Section: Introductionmentioning

confidence: 99%

Composition of cetacean communities worldwide shapes their contribution to ocean nutrient cycling

Gilbert,

Jeanniard-du-Dot,

Authier

et al. 2023

Nat Commun

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Defecation by large whales is known to fertilise oceans with nutrients, stimulating phytoplankton and ecosystem productivity. However, our current understanding of these processes is limited to a few species, nutrients and ecosystems. Here, we investigate the role of cetacean communities in the worldwide biological cycling of two major nutrients and six trace nutrients. We show that cetaceans release more nutrients in mesotrophic to eutrophic temperate waters than in oligotrophic tropical waters, mirroring patterns of ecosystem productivity. The released nutrient cocktails also vary geographically, driven by the composition of cetacean communities. The roles of small cetaceans, deep diving cetaceans and baleen whales differ quantitatively and functionally, with contributions of small cetaceans and deep divers exceeding those of large whales in some areas. The functional diversity of cetacean communities expands beyond their role as top predators to include their role as active nutrient vectors, which might be equally important to local ecosystem dynamics.

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Commercial krill fishing within a foraging supergroup of fin whales in the Southern Ocean

Cited by 8 publications

References 20 publications

Estimated summer abundance and krill consumption of fin whales throughout the Scotia Sea during the 2018/2019 summer season

Estimated summer abundance and krill consumption of fin whales throughout the Scotia Sea during the 2018/2019 summer season

Seasonal acoustic presence of marine mammals at the South Orkney Islands, Scotia Sea

Composition of cetacean communities worldwide shapes their contribution to ocean nutrient cycling

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