Acoustic characterization of automatically detected krill (Euphausia superba) aggregations in the Bransfield Strait and Elephant Island
Keywords:Hydroacoustic, aggregations, Antarctic, multifrequency echosounder SIMRAD EK80, biostatistics
This study shows the characterization of krill (Euphausia superba) aggregations identified in the Bransfield Strait and around of Elephant Island. Data were collected using a multifrequency SIMRAD EK80 echosounder during three austral summers: 2018, 2019 and 2020. For detection of krill aggregations, two frequencies (38 and 120 kHz) and an automated Echoview version 9 algorithm with the EchoviewR package in R were used. A total of 22,221 aggregations were detected. Acoustic descriptors were analyzed with Pearson’s correlation. For the characterization of krill aggregations, principal component analysis (PCA) was applied, followed by hierarchical clustering. To determine temporal differences of clusters, an ANOVA was applied. In addition, krill aggregations were assigned to surface environmental variables to apply a generalized additive model (GAM). Three clusters were identified using the first three dimensions of the PCA (which explained 81% of the total variability). The first cluster was characterized by krill aggregations having lower height (2 m), backscattering acoustic energy (7 m2 mn-2), and being located at a greater depth (81 m). The second cluster had the shallowest swarms (34 m), shortest length (75 m) and compactness (202). Finally, the third cluster had the largest swarms in length (849 m), volume (207,412 m3) and height (11 m); in addition of having greater acoustic energy (637 m2 mn-2), obliquity (6), compactness (2,436) and coefficient of variation (213). Spatially, cluster I was located with a greater presence around Elephant Island during 2018 and 2019, while for the same period, clusters I and II were located scattered throughout the study area but focused on the Bransfield Strait. By 2020, thermal anomalies of approximately + 2 °C were presented and a dispersion of the three clusters was noted throughout the study area, where cluster I was located with a greater presence in the Bransfield Strait. Significant differences (p < 0.05) were found among the clusters per year. However, such differences were not so marked. Through a GAM, it was determined that all variables for each cluster were significant (p < 0.05). Swarms were kept in average conditions of temperature (0.8 °C), salinity (34.14) and dissolved oxygen (8.16 ml l-1). On an interannual scale, it was observed that the characteristics of aggregations remained unchanged.
Agnew D. 1992. Distribution of krill (Euphausia superba Dana) catches in the South Shetlands and South Orkneys. Selected scientific papers SC-CAMLR-SSP/9. Hobart: CCAMLR. p. 287-303.
Alonso S, Switzer P, Mangel M. 2003. An ecosystem-based approach to management: using individual behavior to predict the indirect effects of Antarctic krill fisheries on penguin foraging. J Appl Ecol. 40: 692-702.
[AMLR] Antarctic Marine Living Resources. 1998. AMLR 1997/1998 Field Season Report. Objectives, accomplishments and tentative conclusions. En: Martin J, editor. Southwest Fisheries Science Center. Antarctic Ecosystem Research Group, Administrative Report LJ- 98-07. 166 p.
[AMLR] Antarctic Marine Living Resources. 2011. AMLR 2009/2010 Field Season Report. Objectives, accomplishments and tentative conclusions. En: Van Cise A, editor. Southwest Fisheries Science Center. Antarctic Ecosystem Research Division NOAA-TM-NMFS-SWFSC-470. 66 p.
Arntz WE. 1997. Investigación antártica en biología marina: situación actual, proyectos internacionales y perspectivas. Bol R Soc Esp Hist Nat. 93 (1-4): 13-44.
Bar-On Y, Philips R, Milo R. 2018. The biomass distribution on Earth. Proc. Natl Acad Sci USA. 115 (25): 6506-6511.
Barrera-Oro E, Marschoff E, Ainley D. 2017. Changing status of three notothenioid fish at the South Shetland Islands (1983-2016) after impacts of the 1970-80s commercial fishery. Polar Biol. 40 (10): 2047-2054. DOI: https://doi.org/10.1007/s00300-017-2125-0
Brierley A, Cox M. 2010. Shapes of krill swarms and fish schools emerge as aggregation members avoid predators and access oxygen. Curr Biol. 20 (19): 1758-1762. DOI: https://doi.org/10.1016/j.cub.2010.08.041
[CCAMLR] Commission for the Conservation of Antarctic Marine Living Resources. 2000. Report of the B0 Workshop. WG-EMM-00/21 Rev. 1. La Jolla.
[CCAMLR] Commission for the Conservation of Antarctic Marine Living Resources. 2007. Report of the XXVI Meeting of the Scientific Committee. SC-CAMLR-XXVI. Hobart: CCAMLR. 4 p.
Conti S, Demer D. 2006. Improved parameterization of the SDWBA for estimating krill target strength. ICES J Mar Sci. 63 (5): 928-935. DOI: https://doi.org/10.1016/j.icesjms.2006.02.007
Cossio A, Reiss C. 2011. Bioacoustics survey. En: Van Cise A, editor. Field Season Report. Objectives, accomplishments and tentative conclusions. AMLR 2009/2010. Southwest Fisheries Science Center. Antarctic Ecosystem Research Division NOAA-TM-NMFS-SWFSC-470. p. 12-16.
Croxall J, Nicol S. 2004. Management of southern ocean fisheries: global forces and future sustainability. Antarct Sci. 16 (4): 569-584.
De Robertis A, Higginbottom I. 2007. A post-processing technique to estimate the signal-to-noise ratio and remove echosounder background noise. ICES J Mar Sci. 64: 1282-1291.
Demer D, Berger L, Bernasconi M, Bethke E, Boswell K, Chu D, Domokos R, Dunford A, Fässler S, Gauthier S, et al. 2015. Calibration of acoustic instruments. ICES Coop Res Rep. 326. 130 p.
Demer D, Conti S. 2005. New target-strength model indicates more krill in the Southern Ocean. ICES J Mar Sci. 62: 25-32.
Foote K. 1990. Spheres for calibrating an eleven-frequency acoustic measurement system. ICES J Mar Sci. 46: 284-286.
Gascon V, Werner R. 2005. Antarctic krill: a case study on the ecosystem implications of fishing. Puerto Madryn: Lighthouse Foundation, Antarctic and Southern Ocean Coalition. 30 p.
Greene C, Stanton T, Wiebe P, McClatchie S. 1991. Acoustic estimates of Antarctic krill. Nature. 349 (6305): 110-110. DOI: https://doi.org/10.1038/349110a0
Greenlaw C, Johnson R. 1983. Multiple frequency acoustical estimation. Biol Ocean. 2 (2, 3-4): 227-252.
Harrison L, Cox MJ, Skaret G, Harcourt R. 2015. The R package EchoviewR for automated processing of active acoustic data using Echoview.
Helbling E, Amos A, Silva N, Villafane V, Holm-Hansen O. 1993. Phytoplankton distribution and abundance as related to a frontal system north of Elephant Island, Antarctica. Antarctic Sci. (1): 25-36.
Hewitt R, Kim S, Naganobu M, Gutierrez M, Kang D, Takao Y, Quinones J, Leeg YH, Shing H, Kawaguchi S, Emery J, Demer D, Loeb V. 2004. Variation in the biomass density and demography of Antarctic krill in the vicinity of the South Shetland Islands during the 1999/2000 austral summer. Deep-Sea Res (II Top Stud Oceanogr). 51: 1411-1419.
Holm-Hansen O, Hewes CD, Villafañe VE, Helbling EW, Silva N, Amos T. 1997. Distribution of phytoplankton and nutrients in relation to different water masses in the area around Elephant Island, Antarctica. Polar Biol. 18 (2): 145-153. DOI: https://doi.org/10.1007/s003000050169
[IMARPE] Instituto del Mar del Perú. 2020. Estudio del ecosistema pelágico en el Estrecho de Bransfield y alrededores de las Islas Piloto Pardo. Vigésimo Séptima Expedición Científica Peruana a La Antártida: ANTAR XXVII.
Kalinowski J, Witek Z. 1985. Scheme for classifying aggregations of Antarctic krill. Biomass Handbook 27. 9 p.
Kock K. 1991. The state of exploitation fish stocks in the Southern Ocean-A review. Arch Fishchereiwiss. 41 (1): 1-66.
Krafft B, Melle W, Knutsen T, Bagøien E, Broms C, Ellertsen B, Siegel V. 2010. Distribution and demography of Antarctic krill in the Southeast Atlantic sector of the Southern Ocean during the austral summer 2008. Polar Biol. 33 (7): 957-968. DOI: https://doi.org/10.1007/s00300-010-0774-3
Macaulay M. 1987. Biomass estimates of krill in the Bransfield Strait-Elephant Island ecosystem monitoring area of CCAMLR. SC-CAMLR-VI/BG/46.
Meyer B, Atkinson A, Bernard K, Brierley A, Driscoll R, HILL S, Marchoff E, Maschette D, Perry F, Reiss C, et al. 2020. Successful ecosystem-based management of Antarctic krill should address uncertainties in krill recruitment, behaviour and ecological adaptation. Commun Earth Environ. 1 (28). DOI: https://doi.org/10.1038/s43247-020-00026-1
Miller D, Barange M, Klindt H, Murray A, Hampton I, Siegel V. 1993. Antarctic krill aggregation characteristics from acoustic observations in the Southwest Atlantic Ocean. Mar Biol. 117 (1): 171-183. DOI: https://doi.org/10.1007/bf00346440
Murphy E, Morris D, Watkins J, Priddle J. 1988. Scales of interaction between Antarctic krill and the environment. En: Sahrhage D, editor. Antarctic Ocean and resources variability. Berlin, Heidelberg: Springer-Verlag. p. 120-130.
Nowacek D, Friedlaender A, Halpin N, Hazen E, Johnston D, Read A, Espinasse B, Zhou M, Zhu Y. 2011. Super-aggregations of krill and Humpback whales in Wilhelmina Bay, Antarctic Peninsula. PLoS ONE. 6: e19173.
Pinel-Alloul P. 1995. Spatial heterogeneity as a multiscale characteristic of zooplankton community. Hydrobiology. 300: 17-42.
Reid K, Sims M, White RW, Gillon K. 2004. Spatial distribution of predator/prey interactions in the Scotia Sea: implications for measuring predator-fisheries overlap. Deep-Sea Res. 51: 1383-1396.
Reiss C, Cossio A, Santora J, Dietrich K, Murray A, Mitchell B, Walsh J, Weiss E, Gimpel C, Jones C, Watters G. 2017. Overwinter habitat selection by Antarctic krill under varying sea-ice conditions: implications for top predators and fishery management. Mar Ecol Prog Ser. 568: 1-16. DOI: https://doi.org/10.3354/meps12099
Ritz D. 1994. Social aggregation in pelagic invertebrates. Adv Mar Biol. 30: 155-216.
Ritz D. 2000. Is social aggregation in aquatic crustaceans a strategy to conserve energy? Can J Fish Aquat Sci. 57 (S3): 59-67.
Siegel V, Kawaguchi S, Ward P, Litvinov F, Sushin V, Loeb V, Watkins J. 2004. Krill demography and large-scale distribution in the southwest Atlantic during January/February 2000. Deep-Sea Res (II Top Stud Oceanogr). 51 (12-13): 1253-1273. DOI: https://doi.org/10.1016/j.dsr2.2004.06.013
Simmonds E, Maclennan DN. 2005. Fisheries acoustics: theory and practice. 2nd ed. Oxford: Blackwell. 437 p.
Smetacek V, Nicol S. 2005. Polar ocean ecosystems in a changing world. Nature. 437: 362-368. DOI: https://doi.org/10.1038/nature04161
Tarling G, Jarvis T, Emsley S, Matthews J. 2002. Midnight sinking behavior in Calanus finmarchicus, a response to satiation or krill predation? Mar Ecol Prog Ser. 240: 183-194.
Tarling G, Klevjer T, Fielding S, Watkins J, Atkinson A, Murphy E, Korb R, Whitehouse M, Leaper R. 2009. Variability and predictability of Antarctic krill swarm structure. Deep-Sea Res (II Top Stud Oceanogr). 56 (11): 1994-2012. DOI: https://doi.org/10.1016/j.dsr.2009.07.004
Trathan P, Hill S. 2016. The importance of krill predation in the Southern Ocean. En: Siegel V, editor. Biology and ecology of Antarctic krill. Springer. p. 321-350.
Trathan P, Warwick-Evans V, Hinke J, Young E, Murphy E, Carneiro A, Dias M, Kovacs K, Lowther A, Godo O, et al. 2018. Managing fishery development in sensitive ecosystems: identifying penguin habitat use to direct management in Antarctica. Ecosphere. 9: e02392.
Villafañe VE, Helbling EW, Holm-Hansen O. 1993. Phytoplankton around Elephant Island, Antarctica. Polar Biol. DOI: https://doi.org/10.1007/bf00238928
Villafañe VE, Helbling EW, Holm-Hansen W. 1995. Spatial and temporal variability of phytoplankton biomass and taxonomic composition around Elephant Island, Antarctica, during the summers of 1990-1993. Mar Biol. 123 (4): 677-686. DOI: https://doi.org/10.1007/bf00349110
Watkins J, Murray A, Daly H. 1999. Variation in the distribution of Antarctic krill Euphausia superba around South Georgia. Mar Ecol Prog Ser. 188: 149-160. DOI: https://doi.org/10.3354/meps188149
Wiebe P, Greene C, Stanton T, Burczynski J. 1990. Sound scattering by live zooplankton and micronekton: empirical studies with a dual-beam acoustical system. J Acoust Soc Am. 88 (5): 2346-2360.
Zhou M, Dorland R. 2004. Aggregation and vertical migration behavior of Euphausia superba. Deep-Sea Res (II Top Stud Oceanogr). 51 (17-19): 2119-2137. DOI: https://doi.org/10.1016/j.dsr2.2004.07.009
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