ADCP measurements of the distribution and abundance of euphausiids near the Antarctic Peninsula in winter

Zhou, Meng; Nordhausen, Walter; Huntley, Mark E.

doi:10.1016/0967-0637(94)90106-6

Cited by 91 publications

(95 citation statements)

References 26 publications

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“…Such changes in the upper metres of the water column could not be detected by Cisewski et al (2010), because they did not sample above 20 m water depth. Similar limitations apply to other studies using acoustic sensors (Brierley et al, , 1998Zhou et al, 1994), as well as net-based investigations integrating the upper 50-300 m in a single density figure (Boysen-Ennen and Piatkowski, 1988;Fisher et al, 2004;Lancraft et al, 2004;Siegel, 2012). Within the range of uncertainty that is associated with the limitations of the acoustic method in resolving the near-surface layer and in discriminating species, the results of this study are however consistent with the DVM annual time series of Cisewski et al (2010).…”

Section: Significance Of the Surface Layer Habitatsupporting

confidence: 69%

Seasonal changes in the vertical distribution and community structure of Antarctic macrozooplankton and micronekton

Flores

Hunt

Kruse

et al. 2014

Deep Sea Research Part I: Oceanographic Research Papers

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This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. b s t r a c tThe macrozooplankton and micronekton community of the Lazarev Sea (Southern Ocean) was investigated at 3 depth layers during austral summer, autumn and winter: (1) the surface layer (0-2 m); (2) the epipelagic layer (0-200 m); and (3) the deep layer (0-3000 m). Altogether, 132 species were identified. Species composition changed with depth from a euphausiid-dominated community in the surface layer, via a siphonophore-dominated community in the epipelagic layer, to a chaetognathdominated community in the deep layer. The surface layer community predominantly changed along gradients of surface water temperature and sea ice parameters, whereas the epipelagic community mainly changed along hydrographical gradients. Although representing only 1% of the depth range of the epipelagic layer, mean per-area macrofauna densities in the surface layer ranged at 8% of corresponding epipelagic densities in summer, 6% in autumn, and 24% in winter. Seasonal shifts of these proportional densities in abundant species indicated different strategies in the use of the surface layer, including both hibernal downward and hibernal upward shift in the vertical distribution, as well as year-round surface layer use by Antarctic krill. These findings imply that the surface layer, especially when it is ice-covered, is an important functional node of the pelagic ecosystem that has been underestimated by conventional depth-integrated sampling in the past. The exposure of this key habitat to climate-driven forces most likely adds to the known susceptibility of Antarctic pelagic ecosystems to temperature rise and changing sea ice conditions.

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Section: Significance Of the Surface Layer Habitatsupporting

confidence: 69%

Seasonal changes in the vertical distribution and community structure of Antarctic macrozooplankton and micronekton

Flores

Hunt

Kruse

et al. 2014

Deep Sea Research Part I: Oceanographic Research Papers

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“…Larger animals would also produce higher observed volume backscattering levels, and the greater offset between observed and predicted volume backscattering at higher scattering levels may support the notion that avoidance partially explains the difference between the two. Similar to the present results, Zhou et al (1994) found that volume backscattering levels predicted from net catches of euphausiids became increasingly smaller than levels observed with an ADCP for higher observed values, which they attributed to avoidance on the part of the euphausiids.…”

Section: 42d Transport and Retention Of Zooplankton And Micronektonsupporting

confidence: 79%

“…Adult Antarctic krill are capable of sustained swimming at 10 to 15 cm s - (Kils, 1981), and so in the eight weeks between the fall and winter surveys, could have migrated distances as far as 725 km. Siegel (1988) hypothesized that adult Antarctic krill migrate offshore in spring, returning to coastal areas for the winter perhaps following a food gradient, and an association of zooplankton with coastal waters during winter has been observed in other shelf regions (Siegel 1988(Siegel , 1989Zhou et al, 1994;Lascara et al, 1999). In the present study, we penetrated through the ice close to shore during winter on only limited occasions.…”

Section: 42b Horizontal Migrationsmentioning

confidence: 91%

“…Little is known about the distribution of Antarctic krill or other zooplankton in this area during winter, however, although studies of the nearby Bransfield Strait region have been more numerous (e.g., Siegel 1989;Zhou et al, 1994). In the only previous acoustic survey of the region, Lascara et al (1999) examined Antarctic krill distribution in Marguerite Bay and the region immediately to the north, and found distinct seasonal variability in biomass and vertical distribution, with krill more abundant and found shallower during the summer and spring than fall and winter.…”

Section: Introductionmentioning

confidence: 99%

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Distribution, patchiness, and behavior of Antarctic zooplankton, assessed using multi-frequency acoustic techniques

Lawson¹

2006

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The physical and biological forces that drive zooplankton distribution and patchiness in an antarctic continental shelf region were examined, with particular emphasis on the Antarctic krill, Euphausia superba. This was accomplished by the application of acoustic, video, and environmental sensors during surveys of the region in and around Marguerite Bay, west of the Antarctic Peninsula, in the falls and winters of 2001 and 2002. An important component of the research involved the development and verification of methods for extracting estimates of ecologically-meaningful quantities from measurements of scattered sound. The distribution of acoustic volume backscattering at the single frequency of 120 kHz was first examined as an index of the overall biomass of zooplankton. Distinct spatial and seasonal patterns were observed that coincided with advective features. Improved parameterization was then achieved for a theoretical model of Antarctic krill target strength, the quantity necessary in scaling measurements of scattered sound to estimates of abundance, through direct measurement of all necessary model parameters for krill sampled in the study region and survey period. Methods were developed for identifying and delineating krill aggregations, allowing the distribution of krill to be distinguished from that of the overall zooplankton community. Additional methods were developed and verified for estimating the length, abundance, and biomass of krill in each acoustically-identified aggregation. These methods were applied to multifrequency acoustic survey data, demonstrating strong seasonal, inter-annual, and spatial variability in the distribution of krill biomass. Highest biomass was consistently associated with regions close to land where temperatures at depth were cool. Finally, the morphology, internal structure, and vertical position of individual krill aggregations were examined. The observed patterns of variability in aggregation characteristics between day and night, regions of high versus low food availability, and in the presence or absence of predators, together reinforced the conclusion that aggregation and diel vertical migration represent strategies to avoid visual predators, while also allowing the krill access to shallowly-distributed food resources. The various findings of this work have important implications to the fields of zooplankton acoustics and Antarctic krill ecology, especially in relation to the interactions of the krill with its predators.

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“…Schools in offshore regions may therefore be experiencing more shear stress and are consequently elongated. Similar trends have been suggested for Antarctic krill swarms (Zhou et al, 1994). A further explanation could be that schools in the inshore regions reduce their horizontal dimensions by extending vertically so that they become narrower in shape and are therefore less visible to predators from above.…”

Section: Insight Into Myctophid Ecologysupporting

confidence: 51%

School characteristics of mesopelagic fish at South Georgia

Saunders

Fielding

Thorpe

et al. 2013

Deep Sea Research Part I: Oceanographic Research Papers

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In this paper, we describe the variation in myctophid schools characteristics at South Georgia using multi-frequency acoustic data collected annually between November 2007 and January 2012. We studied the relationship between the proximity of land and the distribution and schooling characteristics of myctophid fish. We also examined patterns in schooling behaviour in relation to oceanographic data. Fish schools were identified using a dualfrequency dB identification method (S v120-38 kHz ), where negative S v120-38 kHz is indicative of gas-bearing organisms, such as swimbladdered fish. Available net data were used to provide information on the meosopelagic fish community in the region. School morphometrics (e.g. length, thickness, area) data were extracted and pooled according to their distance from the shore (0-30 km, 30-60 km, 60-90 km, 90-120 km). A total of 578 schools were detected in the survey region and there was high variation in school backscattering strength (NASC), length, height, perimeter, depth and horizontal distribution between surveys, including distinct inter-annual variation in these parameters when surveys were conducted in the same season (2009)(2010)(2011)(2012). Schools were distributed predominantly on-shelf (0-500 m isobaths) during some summer surveys (2007 and 2012) and predominantly off-shelf on others (>500 2 m isobaths; 2009, 2010 and 2011). There was also evidence of bathymetric separation in the horizontal distribution of schools. Schools observed in the late-season in 2008 had the greatest NASC, largest height and the deepest depth distribution. Most schools occurred at depths between ~60-300 m, but they did not occupy the same water masses during each survey. Schools became progressively thinner, shallower and acoustically weaker with increasing distance to land, whilst school length and perimeter increased correspondingly.The change in fish schooling behaviour between environments could be a response to a combination of local predatory threats over short spatial/temporal scales and differences in oceanographic conditions, such as current velocity. The trend could also be evidence of spatial habitat partitioning of myctophids, with different schooling species, or different lifestages, orientating along a bathymetric gradient at South Georgia.

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ADCP measurements of the distribution and abundance of euphausiids near the Antarctic Peninsula in winter

Cited by 91 publications

References 26 publications

Seasonal changes in the vertical distribution and community structure of Antarctic macrozooplankton and micronekton

Seasonal changes in the vertical distribution and community structure of Antarctic macrozooplankton and micronekton

Distribution, patchiness, and behavior of Antarctic zooplankton, assessed using multi-frequency acoustic techniques

School characteristics of mesopelagic fish at South Georgia

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