scholarly journals Complementary use of stable isotopes and fatty acids for quantitative diet estimation of sympatric predators, the Antarctic pack-ice seals

Oecologia ◽  
2021 ◽  
Author(s):  
A. I. Guerrero ◽  
A. Pinnock ◽  
J. Negrete ◽  
T. L. Rogers
Keyword(s):  
Stable Isotopes ◽  
Euphausia Superba ◽  
Weddell Seal ◽  
Leopard Seal ◽  
Pleuragramma Antarcticum ◽  
Secondary Sources ◽  
Important Prey ◽  
Pack Ice ◽  
Feasible Option ◽  
Quantitative Manner

AbstractThe quantitative use of stable isotopes (SIs) for trophic studies has seen a rapid growth whereas fatty acid (FA) studies remain mostly qualitative. We apply the Bayesian tool MixSIAR to both SI and FA data to estimate the diet of three sympatric predators: the crabeater (Lobodon carcinophaga), Weddell (Leptonychotes weddellii) and leopard seal (Hydrurga leptonyx). We used SI data of their vibrissae and FA data of their outer blubber to produce comparable diet estimates for the same individuals. Both SI and FA models predicted the same main diet components, although the predicted proportions differed. For the crabeater seal, both methods identified krill, Euphausia superba, as the main, and almost exclusive, food item, although the FA model estimated a slightly lower proportion, potentially due to the low lipid content of krill compared to the fish species used in the model. For the Weddell seal the FA model identified the fish Pleuragramma antarcticum as the most important prey, whereas the SI model was not able to distinguish among prey species, identifying a ‘fish-squid’ group as the main diet component. For the leopard seal, both models identified krill as the main contributor; however, the predicted proportions for the secondary sources differed. Although vibrissae and outer blubber may not represent the same timeframe, the use of MixSIAR with FA data provides diet estimates comparable to those obtained with SI data, thus, both approaches were complimentary. The use of both biotracers offers a feasible option to study diets of wild animals in a quantitative manner.

Contribution to the biology of squid in the Prydz Bay region, Antarctica

1994 ◽  
Vol 6 (2) ◽  
pp. 223-229 ◽  
Author(s):  
C.C. Lu ◽  
R. Williams
Keyword(s):  
Euphausia Superba ◽  
Common Species ◽  
Total Weight ◽  
Mantle Length ◽  
Prydz Bay ◽  
Pleuragramma Antarcticum ◽  
Size Frequency Distribution ◽  
Important Prey ◽  
Vertical Distributions ◽  
Ocean Sector

The teuthoid fauna of the Prydz Bay region of the Southern Ocean (Indian Ocean sector) has been studied based on the material collected from 1981–1991 using a rectangular midwater trawl (RMT-8), pelagic trawl (IYGPT), and bottom trawl. Eight species of squid have been recognized: Brachioteuthis sp., Kondakovia longimana, Bathyteuthis abyssicola, Psychroteuthis glacialis, Alluroteuthis antarcticus, Mastigoteuthis psychrophila, Mesonychoteuthis hamiltoni and Galiteuthis glacialis. Size frequency distribution, geographical and vertical distributions of each species as well as diets of common species are analysed. There is no evidence of a diel vertical migration but ontogenetic descent appears to occur in P. glacialis and G. glacialis. Antarctic krill, Euphausia superba and the Antarctic silverfish, Pleuragramma antarcticum are important prey for most species with cannibalism occurring in P. glacialis, A. antarcticus and M. hamiltoni. Equations for calculating total weight from mantle length, and mantle length and total weight from upper and lower rostral length are provided for B. abyssicola, P. glacialis, A. antarcticus, M. psychrophila, and G. glacialis.

Stable isotopes identify an ontogenetic niche expansion in Antarctic krill (Euphausia superba) from the South Shetland Islands, Antarctica

2013 ◽  
Vol 160 (6) ◽  
pp. 1311-1323 ◽  
Author(s):  
Michael J. Polito ◽  
Christian S. Reiss ◽  
Wayne Z. Trivelpiece ◽  
William P. Patterson ◽  
Steven D. Emslie
Keyword(s):  
Stable Isotopes ◽  
Antarctic Krill ◽  
Euphausia Superba ◽  
South Shetland Islands ◽  
The South ◽  
Niche Expansion ◽  
Shetland Islands ◽  
Ontogenetic Niche ◽  
Antarctic Krill Euphausia Superba

Spring distribution, size composition and behaviour of krill Euphausia superba in the western Weddell Sea

Polar Record ◽  
1990 ◽  
Vol 26 (157) ◽  
pp. 85-89 ◽  
Author(s):  
B.I. Bergström ◽  
G. Hempel ◽  
H.-P. Marschall ◽  
A. North ◽  
V. Siegel ◽  
...  
Keyword(s):  
Algal Growth ◽  
Size Composition ◽  
Water Layer ◽  
Open Water ◽  
Euphausia Superba ◽  
Weddell Sea ◽  
Ice Algae ◽  
Remotely Operated Vehicle ◽  
Direct Observations ◽  
Pack Ice

AbstractDistribution, size composition and behaviour of Euphausia superba were investigated in the northwestern Weddell Sea (59–63°S, 45–52°W) in October-November 1988 using RMT trawling, SCUBA diving and visual examination of the ice undersurface using a remotely-operated vehicle (ROV). Amounts of krill washed onto the ice during ice-breaking along transects were noted. Juvenile and sub-adult krill were found, often in high numbers, in association with seasonal pack-ice, from the outer marginal ice zone to at least 200 nautical miles [3 50 km] into the closed pack-ice zone. Krill caught with the RMT or observed within or close to the ice usually had full guts. They were frequently seen feeding on ice algae, and seemed to concentrate in pressure zones, melting ice and infiltration layers, ie where ice provided both confining crevices and rich algal growth. During twilight numbers of krill increased in open water close to the ice, though ROV observations at night revealed even greater numbers remaining in ice cavities. Direct observations from deck, by divers and by ROV, confirmed that most of the krill population in the uppermost water layer was confined to ice habitats, though in three out of 20 RMT catches krill reached densities of 0.1 nr3 ie normal summer values. ‘Miniswarms’ forming in early November may indicate seasonal transition of at least part of the krill population from winter ice habitat and grazing on ice-algae, to summer pelagic life and filter-feeding on phytoplankton.

scholarly journals The diet of white-chinned petrels Procellaria aequinoctialis, Linnaeus 1758, in years of contrasting prey availability at South Georgia

1999 ◽  
Vol 11 (3) ◽  
pp. 283-292 ◽  
Author(s):  
Simon D. Berrow ◽  
John P. Croxall
Keyword(s):  
Breeding Success ◽  
Prey Item ◽  
Prey Availability ◽  
Euphausia Superba ◽  
Feeding Frequency ◽  
South Georgia ◽  
Important Prey ◽  
Breeding Failure ◽  
Feeding Methods ◽  
Procellaria Aequinoctialis

The diet of breeding white-chinned petrels was studied during the summers of 1996 and 1998 at South Georgia. Krill abundance/availability was high throughout 1996 but apparently low at the beginning of the 1998 breeding season. The diet of white-chinned petrels was similar between years and consistent with previous studies. Krill Euphausia superba (41–42% by weight) was the single most important prey item followed by fish (39–29%) and squid (19–25%). Meal mass was consistent (110 g in 1996, 119 g in 1998) between years but a significant decrease (46%) in feeding frequency in 1998 (0.54 meals day−1 compared to 0.75 meals day−1 in 1996) resulted in 19% less food delivered to chicks in 1998 than in 1996. Breeding success, however, was consistent between years at 44% and similar to that recorded previously at Bird Island. This is in contrast to black-browed and grey-headed albatrosses, both of which experienced almost total breeding failure in 1998. It is suggested that their varied and versatile feeding methods, together with their greater diving ability, capacity to feed at night and extensive foraging range, help white-chinned petrels minimise the effects of krill shortage.

Introduction

2007 ◽  
pp. 1-24
Author(s):  
A.B. Dickinson
Keyword(s):  
Weddell Seal ◽  
Elephant Seal ◽  
Falkland Islands ◽  
Leopard Seal ◽  
Sea Lion ◽  
Crabeater Seal ◽  
Fur Seal

This chapter introduces the structure and aim of the volume. It begins with an overview of the history and topography of the Falkland Islands and Dependencies, then discusses the sources of revenue on the islands, and confirming that sealing no longer occurs within the jurisdiction. It then introduces the development of commercial sealing: fishing locations; seal products - primarily meat, skin, fur, and oil; costs and profits; and the conditions aboard sealing vessels. It also provides a detailed description of different seal breeds - listing individually their habitats, features, region, uses, and profitability. The species of Falklands seals detailed are the Fur Seal; Bull and Cow Elephant Seal; Elephant Seal; Sea Lion; Leopard Seal; Weddell Seal; and Crabeater Seal. It concludes that all of the species of seals listed now enjoy protection in the Falklands, before lamenting that contemporary data concerning population figures is imprecise.

scholarly journals Summer circumpolar acoustic occurrence and call rates of Ross, Ommatophoca rossii, and leopard, Hydrurga leptonyx, seals in the Southern Ocean

Polar Biology ◽  
2021 ◽  
Vol 44 (2) ◽  
pp. 433-450
Author(s):  
Fannie W. Shabangu ◽  
Tracey L. Rogers
Keyword(s):  
Southern Ocean ◽  
Austral Summer ◽  
Call Rate ◽  
Leopard Seal ◽  
Survey Techniques ◽  
Pack Ice ◽  
Hydrurga Leptonyx ◽  
Spatio Temporal ◽  
The Antarctic ◽  
Temporal Overlap

Abstract Two of the Antarctic pack ice seals, Ross, Ommatophoca rossii, and leopard, Hydrurga leptonyx, seals, are extremely difficult to study via traditional visual survey techniques, yet are ideal for an acoustic survey as they are highly vociferous and produce an array of underwater sounds during the austral summer. To determine their acoustic occurrence in the Antarctic pack ice, we use their calls, detected within 680 acoustic recordings made between 1999 and 2009 as part of two multinational programmes. Siren calls of Ross seals were detected mainly in January, and 9.88 calls per minute from low siren calls was the highest call rate for this species. High numbers of Ross seal calls were detected close to the ice edge in areas between 0° and 20° E and 60° and 130° E, suggesting these are important summer habitats. Leopard seal calls were detected mainly in December and January, and December had the highest percentage of calls. Call rate of 11.93 calls per minute from low double trills was the highest call rate for leopard seals. Leopard seal calls were detected throughout the Southern Ocean with more calls detected throughout the pack ice. There was little spatio-temporal overlap in call occurrence of Ross and leopard seals, but both species were more vocally active during the day. Longitude and latitude were the most important predictors of Ross seal occurrence, and month of the year highly predicted leopard seal occurrence. This is the first study to examine the circumpolar acoustic occurrence of Ross and leopard seals in the Southern Ocean pack ice.

Over-winter movements and diving behavior of female Weddell seals (Leptonychotes weddellii) in the southwestern Ross Sea, Antarctica

1994 ◽  
Vol 72 (10) ◽  
pp. 1700-1710 ◽  
Author(s):  
J. Ward Testa
Keyword(s):  
Ross Sea ◽  
Diving Behavior ◽  
Winter Period ◽  
Pleuragramma Antarcticum ◽  
Long Distance ◽  
Leptonychotes Weddellii ◽  
Mcmurdo Sound ◽  
Weddell Seals ◽  
Pack Ice ◽  
Fast Ice

The movements and diving behavior of 18 adult female Weddell seals (Leptonychotes weddellii) were determined by satellite telemetry during the over-winter period in 1990 and 1991. Nine seals provided diving and movement data for 8 – 9 months. Seals that normally bred in the eastern part of McMurdo Sound spent most of the winter in the middle and northern parts of McMurdo Sound before the annual shore-fast ice had formed in those areas, or in the pack ice 0–50 km north of the sound and Ross Island. This is a greater use of pack ice, as opposed to shore-fast ice, in winter than was previously believed. Some long-distance movements (one over 1500 km in total) to the middle and northwestern parts of the Ross Sea also occurred. Although highly variable within and between individuals, dives indicative of foraging were primarily to mid-water regions (100 – 350 m) in both years, and were similar to those that have been observed in spring and summer, when Pleuragramma antarcticum is the primary prey of Weddell seals in McMurdo Sound.

scholarly journals Antarctic Radiocarbon Reservoir: The Case of the Mummified Crabeater Seals (Lobodon Carcinophaga) in Bodman Cape, Seymour Island, Antarctica

Radiocarbon ◽  
2011 ◽  
Vol 53 (1) ◽  
pp. 161-166 ◽  
Author(s):  
Javier Negrete ◽  
Esteban Soibelzon ◽  
Eduardo P Tonni ◽  
Alejandro Carlini ◽  
Leopoldo H Soibelzon ◽  
...  
Keyword(s):  
Geographical Location ◽  
Euphausia Superba ◽  
Death Event ◽  
Pack Ice ◽  
Seal Population ◽  
Antarctic Seals ◽  
Antarctic Continent ◽  
Crabeater Seals ◽  
The Antarctic ◽  
Reservoir Age

At least 50% of the world's seal population is distributed in the pack-ice region surrounding Antarctica. Among the Antarctic seals, Lobodon carcinophaga (commonly known as “crabeater seals”) are the most abundant. This is a krill-feeding species, subsisting primarily on Euphausia superba. The occurrence of mummified seals has been documented since 1900 in several Antarctic regions, and different hypotheses about age and what happened to them have been proposed. Taking into account the depletion of 14C concentration in marine waters, we dated a recently deceased and a mummified L. carcinophaga along with a mollusk (Nacella concinna) collected alive from different locations around Antarctica. We discuss their relationship in light of the 14C reservoir. The age obtained for the recently deceased crabeater seals suggests a reservoir age of around 1300 yr for these waters, which is in agreement with the correction value for reservoir age obtained for the same species in the area. We applied this reservoir correction value to the conventional age of 1180 14C yr BP obtained for the mummified seal. The results indicate that the death event probably occurred within the last 100 yr. The age obtained for the mollusk specimen confirms that the correction values of the reservoir effect for the Antarctic continent vary according to geographical location and to the type of sample dated.

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