Diet, provisioning and productivity responses of marine predators to differences in availability of Antarctic krill

Croxall, John P.; Reid, Keith; Prince, P. A.

doi:10.3354/meps177115

Cited by 315 publications

(236 citation statements)

References 26 publications

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“…Local krill ¶ One study of fish meals made from by-products of the Alaska fishing industry revealed no detectable levels of PCBs or other contaminants (58). depletion caused by fishing could also significantly reduce the food resources of other predators, such as seals and whales (70). Unfortunately, existing data on krill abundance and population variables are not sufficient to establish precautionary management of the krill fishery and its effect on the Antarctic ecosystem.…”

Section: Alternatives To Forage Fishmentioning

confidence: 99%

Feeding aquaculture in an era of finite resources

Naylor

Hardy²,

Bureau³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

1,192

865

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Aquaculture's pressure on forage fisheries remains hotly contested. This article reviews trends in fishmeal and fish oil use in industrial aquafeeds, showing reduced inclusion rates but greater total use associated with increased aquaculture production and demand for fish high in long-chain omega-3 oils. The ratio of wild fisheries inputs to farmed fish output has fallen to 0.63 for the aquaculture sector as a whole but remains as high as 5.0 for Atlantic salmon. Various plant- and animal-based alternatives are now used or available for industrial aquafeeds, depending on relative prices and consumer acceptance, and the outlook for single-cell organisms to replace fish oil is promising. With appropriate economic and regulatory incentives, the transition toward alternative feedstuffs could accelerate, paving the way for a consensus that aquaculture is aiding the ocean, not depleting it.

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Section: Alternatives To Forage Fishmentioning

confidence: 99%

Feeding aquaculture in an era of finite resources

Naylor

Hardy²,

Bureau³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

1,192

865

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“…A ntarctic krill Euphausia superba, a key species in Southern Ocean food webs 1 , plays a central role in ecosystem processes and community dynamics of apex predators, and is the target of a commercial fishery 2 . Krill spawn in late spring and their larvae develop during summer, autumn and under the ice in winter to emerge as juveniles in the following spring.…”

mentioning

confidence: 99%

The winter pack-ice zone provides a sheltered but food-poor habitat for larval Antarctic krill

et al. 2017

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A ntarctic krill Euphausia superba, a key species in Southern Ocean food webs 1 , plays a central role in ecosystem processes and community dynamics of apex predators, and is the target of a commercial fishery 2 . Krill spawn in late spring and their larvae develop during summer, autumn and under the ice in winter to emerge as juveniles in the following spring. The newly spawned eggs sink from the surface to up to 1,000 m depth where they hatch and the developing larvae actively swim upwards to feed in the upper water column 1 . Larval Antarctic krill have low lipid reserves, which are insufficient to support long periods of starvation. Therefore, winter, when primary production is minimal, is assumed to be a critical bottleneck for larval krill development and hence recruitment to the adult population 3,4 . Present hypotheses suggest that high algal biomass in winter sea ice enhances larval krill winter-feeding conditions and growth [5][6][7][8] . This implies that larvae have access to this high algal biomass within the sea ice. However, recent observations 9,10 indicate that the linkage between sea ice and krill recruitment success is not as direct as has been suggested. The timing of ice-edge advance and annual ice-season duration is highly variable, and does not necessarily show a clear link to krill recruitment in the following year ( Supplementary Figs. 1 and 2). Along the Antarctic Peninsula, adult krill have a five to six year population cycle with oscillations in biomass exceeding an order of magnitude 9 . According to bioenergetics models, part of the variability is due to interannual variation in reproductive output 11 as well as autumn blooms that may govern the possible overwinter survival rate of larvae 11,12 . In the Bransfield Strait, three krill winter surveys have shown that krill abundance is an order of magnitude higher than in summer, regardless of concurrent sea-ice conditions 10 A dominant Antarctic ecological paradigm suggests that winter sea ice is generally the main feeding ground for krill larvae. Observations from our winter cruise to the southwest Atlantic sector of the Southern Ocean contradict this view and present the first evidence that the pack-ice zone is a food-poor habitat for larval development. In contrast, the more open marginal ice zone provides a more favourable food environment for high larval krill growth rates. We found that complex under-ice habitats are, however, vital for larval krill when water column productivity is limited by light, by providing structures that offer protection from predators and to collect organic material released from the ice. The larvae feed on this sparse ice-associated food during the day. After sunset, they migrate into the water below the ice (upper 20 m) and drift away from the ice areas where they have previously fed. Model analyses indicate that this behaviour increases both food uptake in a patchy food environment and the likelihood of overwinter transport to areas where feeding conditions are more favourable in spring.

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“…1(a)], experiences dramatic interannual variability in its ecosystem. This variability is connected to fluctuations in the local abundance of Antarctic krill (Euphausia superba), the main food source of the higher predators that breed on South Georgia (Croxall et al, 1988(Croxall et al, , 1999Boyd et al, 1994). The krill population at South Georgia is believed not to be self-sustaining (Everson, 1984) but to be maintained instead by oceanic transport of krill from recognised breeding grounds upstream of South Georgia in the vicinity of the Antarctic Peninsula, the South Orkney Islands and the Weddell Sea (e.g.…”

Section: Introductionmentioning

confidence: 99%

Variability of the southern Antarctic Circumpolar Current front north of South Georgia

Thorpe

Heywood

Brandon

et al. 2002

Journal of Marine Systems

113

108

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South Georgia ( f 54jS, 37jW) is an island in the eastern Scotia Sea, South Atlantic that lies in the path of the Antarctic Circumpolar Current (ACC). The southern ACC front (SACCF), one of three major fronts associated with the ACC, wraps anticyclonically around South Georgia and then retroflects north of the island. This paper investigates temporal variability in the position of the SACCF north of South Georgia that is likely to have an effect on the South Georgia ecosystem by contributing to the variability in local krill abundance.A meridional hydrographic section that crossed the SACCF three times demonstrates that the SACCF is associated with a geopotential anomaly of 4.5 J kg À 1 in the eastern Scotia Sea. A high resolution (1/4j Â 1/4j) map of historical geopotential anomaly shows the mean position of the SACCF retroflection north of South Georgia to be at 36jW, 400 km further east than in previous work. It also reveals temporal variability associated with the SACCF in the South Georgia region. A near-surface drifter provides evidence for variability in the western extent of the SACCF north of South Georgia and for the presence of eddies in the region. Output from a 3-year (1993 -1995) high frequency wind forced run of the eddy-permitting Ocean Circulation and Climate Advanced Modelling project (OCCAM) model, used to investigate the frontal variability, shows two periods of anomalous westward extent of the SACCF north of South Georgia and associated eddy-shedding. The SACCF variability affects the near-surface transport of passive drifters into the region with implications for the South Georgia ecosystem. D

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Diet, provisioning and productivity responses of marine predators to differences in availability of Antarctic krill

Cited by 315 publications

References 26 publications

Feeding aquaculture in an era of finite resources

Feeding aquaculture in an era of finite resources

The winter pack-ice zone provides a sheltered but food-poor habitat for larval Antarctic krill

Variability of the southern Antarctic Circumpolar Current front north of South Georgia

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