Regional differences in quality of krill and fish as prey along the Western Antarctic Peninsula

Ruck, Kate E.; Steinberg, Deborah K.; Canuel, Elizabeth A.

doi:10.3354/meps10868

Cited by 33 publications

(39 citation statements)

References 68 publications

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“…Myctophids in the Scotia Sea attain body sizes between ∼55 and 170 mm (standard length; SL) and have life cycles lasting between 2 and 7 years (Greely et al, 1999) ( Table 1). All species in this region have a relatively high energy content and are suitable as prey for most higher predators in terms of their size spectra and their availability in the region across multiple years and seasons (Ruck et al, 2014). Myctophids that attain a size sufficient to consume large (>40 mm) macrozooplankton, such as krill and large amphipods, include N. achirus, and the Electrona and Gymnoscopelus species.…”

Section: Life Cycle Characteristicsmentioning

confidence: 99%

Myctophid Fish (Family Myctophidae) Are Central Consumers in the Food Web of the Scotia Sea (Southern Ocean)

et al. 2019

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Myctophids are the most abundant and diverse mesopelagic fishes in the Southern Ocean. They are a conduit of energy between primary consumers and higher marine predators, and between the surface layers and the mesopelagic depths. However, there remain major uncertainties about their ecology, particularly regarding their role in Southern Ocean food webs in waters south of the Antarctic Polar Front, which are often regarded as dominated by Antarctic krill. Limited data on the feeding ecology of myctophids has made it difficult to assess the importance of myctophids as consumers of krill and how they fit in the traditional view of a krill-dominated system (diatom-krillhigher predator). We provide a new assessment of the role of myctophids in Southern Ocean food webs using information from recent trophodynamic studies of myctophids conducted in the Scotia Sea, one of the most productive regions of the Southern Ocean and a region that sustains both major populations of higher predators (sea birds, seals, whales) and important commercial fisheries (krill, toothfish, and mackerel icefish). Collectively, these data show that myctophids have a central role in Southern Ocean food webs as both predators and prey. Large myctophid species are prevalent consumers of krill throughout their distributional range and in different seasons in the Scotia Sea. Moreover, best estimates of both myctophid and higher predator consumption of krill to date indicate that large myctophids are the greatest predators of krill in this region, consuming almost as much krill as do all other vertebrates. Nevertheless, there are several smaller myctophid species that do not eat krill, instead consuming copepods and other small euphausiids. Myctophids therefore link primary producers to higher predators through both krill-dependent and krill-independent trophic pathways, emphasizing their importance in regional food webs. Consequently, trophic pathways involving large myctophids are unlikely to be exempt from the direct consequences of projected redistribution and/or reduction in krill population biomass under scenarios of ocean-warming, whilst trophic pathways involving small myctophids may be more resilient to such effects and become increasingly important to higher trophic levels. Further studies are required to determine the extent to which myctophids can maintain food web stability and sustain higher predator populations Frontiers in Marine Science | www.frontiersin.org 1 September 2019 | Volume 6 | Article 530 Saunders et al. Trophodynamics of Scotia Sea Myctophidsduring periods of prolonged reductions in krill abundance. Including knowledge of the role of myctophids in Southern Ocean food webs will be important for developing robust projections of the impacts of future change to inform decision making for conservation and management.

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Section: Life Cycle Characteristicsmentioning

confidence: 99%

Myctophid Fish (Family Myctophidae) Are Central Consumers in the Food Web of the Scotia Sea (Southern Ocean)

et al. 2019

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“…Spatial differences in prey nutritive value, as well as temporal differences, have also been shown to have important implications for predators. Ruck et al (2014) showed that across all sexes and maturity stages, krill in the southern part of the Palmer study region had higher total lipid content than that in the north. This regional variability in prey quality could affect the ability of apex predators to meet their energetic demands.…”

Section: Why Do We Need To Know About Krill Consumption? -A Re-evaluamentioning

confidence: 90%

The Importance of Krill Predation in the Southern Ocean

Trathan

Hill

2016

Advances in Polar Ecology

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Antarctic krill is a major prey species for a diverse array of Southern Ocean predators. The amount of krill that predators consume, and how this changes over space and time, is a key issue in understanding both regional and circumpolar aspects of the Southern Ocean foodweb. We assess current knowledge of consumption by the various predator groups, and the ecological processes through which krill and its predators influence each other. Knowledge has improved greatly over recent decades and has revealed a high level of complexity in the processes that govern krill consumption. We focus on the Antarctic Peninsula and Scotia Sea region where both krill and its consumers occur in significant concentrations and where an updated estimate of krill consumption by the main vertebrate groups is 55 million tonnes per year. Research has mainly focused on mammalian and avian predators of post-larval krill, particularly penguins. Potentially important consumer groups like fish, cephalopods and carnivorous zooplankton remain poorly understood, as does consumption of the early life stages of krill. As a consequence of these knowledge gaps and the variability that arises from complexity, a reliable seasonally, spatially or taxonomically resolved description of krill consumption remains elusive. One of the key motivations for attempting to estimate krill consumption is to understand how changes in krill availability impact predator populations.Such understanding is an important requirement for ecosystem based management of the Antarctic krill fishery. We therefore propose that integrated study areas in strategic fishing locations should be developed to directly assess the response of krill predators to changes in krill availability.

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“…The lipid content of E. superba and T. macrura showed a high local variability in several studies (Pond et al 1995; Hagen et al 1996; Mayzaud et al 1998; Färber-Lorda et al 2009a; Färber-Lorda and Mayzaud 2010; Ruck et al 2014; Kohlbach et al 2017). In E. superba lipid, but also protein content, was found to be highly variable within a single population during several seasons, and the variety within a season can be greater than between seasons (Torres et al 1994; Mayzaud et al 1998; Ruck et al 2014). This intra-seasonal variation can be attributed to a patchy and/or regionally variable distribution of available food (Mayzaud et al 1998; Ruck et al 2014; Virtue et al 2016; Schaafsma et al 2017).…”

Section: Energy Density Of Zooplankton and Nekton Speciesmentioning

confidence: 98%

“…Temperature and changes in food can, furthermore, influence the energy storage function of prey species (Ruck et al 2014). Specifically at higher latitudes, the Southern Ocean experiences strong seasonality, with drastic changes in light availability between seasons and massive changes in sea-ice cover in many parts.…”

Section: Introductionmentioning

confidence: 99%

Review: the energetic value of zooplankton and nekton species of the Southern Ocean

Schaafsma¹,

Cherel

Flores

et al. 2018

Mar Biol

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Understanding the energy flux through food webs is important for estimating the capacity of marine ecosystems to support stocks of living resources. The energy density of species involved in trophic energy transfer has been measured in a large number of small studies, scattered over a 40-year publication record. Here, we reviewed energy density records of Southern Ocean zooplankton, nekton and several benthic taxa, including previously unpublished data. Comparing measured taxa, energy densities were highest in myctophid fishes (ranging from 17.1 to 39.3 kJ g−1 DW), intermediate in crustaceans (7.1 to 25.3 kJ g−1 DW), squid (16.2 to 24.0 kJ g−1 DW) and other fish families (14.8 to 29.9 kJ g−1 DW), and lowest in jelly fish (10.8 to 18.0 kJ g−1 DW), polychaetes (9.2 to 14.2 kJ g−1 DW) and chaetognaths (5.0–11.7 kJ g−1 DW). Data reveals differences in energy density within and between species related to size, age and other life cycle parameters. Important taxa in Antarctic food webs, such as copepods, squid and small euphausiids, remain under-sampled. The variability in energy density of Electrona antarctica was likely regional rather than seasonal, although for many species with limited data it remains difficult to disentangle regional and seasonal variability. Models are provided to estimate energy density more quickly using a species’ physical parameters. It will become increasingly important to close knowledge gaps to improve the ability of bioenergetic and food web models to predict changes in the capacity of Antarctic ecosystems to support marine life.Electronic supplementary materialThe online version of this article (10.1007/s00227-018-3386-z) contains supplementary material, which is available to authorized users.

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Regional differences in quality of krill and fish as prey along the Western Antarctic Peninsula

Cited by 33 publications

References 68 publications

Myctophid Fish (Family Myctophidae) Are Central Consumers in the Food Web of the Scotia Sea (Southern Ocean)

Myctophid Fish (Family Myctophidae) Are Central Consumers in the Food Web of the Scotia Sea (Southern Ocean)

The Importance of Krill Predation in the Southern Ocean

Review: the energetic value of zooplankton and nekton species of the Southern Ocean

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