Two scales of distribution and biomass of Antarctic krill (Euphausia superba) in the eastern sector of the CCAMLR Division 58.4.2 (55°E to 80°E)

• Published in: PLOS ONE
• Main Authors: Cox, Martin J., Macaulay, Gavin, Brasier, Madeleine J., Burns, Alicia, Johnson, Olivia J., King, Rob, Maschette, Dale, Melvin, Jessica, Smith, Abigail J. R., Weldrick, Christine K., Wotherspoon, Simon, Kawaguchi, So
• Format: Text
• Language: English
• Published: Public Library of Science 2022
• Subjects: Research Article; Antarctic; Antarc*; Antarctic Krill; Euphausia superba
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9401115/; https://doi.org/10.1371/journal.pone.0271078

Regular monitoring is an important component of the successful management of pelagic animals of interest to commercial fisheries. Here we provide a biomass estimate for Antarctic krill (Euphausia superba) in the eastern sector of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) Division 58.4.2 (55°E to 80°E; area = 775,732 km(2)) using data collected during an acoustic-trawl survey carried out in February and March 2021. Using acoustic data collected in day-time and trawl data, areal biomass density was estimated as 8.3 gm(-2) giving a total areal krill biomass of 6.48 million tonnes, with a 28.9% coefficient of variation (CV). The inaccessibility of the East Antarctic makes fisheries-independent surveys of Antarctic krill expensive and time consuming, so we also assessed the efficacy of extrapolating smaller surveys to a wider area. During the large-scale survey a smaller scale survey (centre coordinates -66.28°S 63.35°E, area = 4,902 km(2)) was conducted. We examine how representative krill densities from the small-scale (Mawson box) survey were over a latitudinal range by comparing krill densities from the large-scale survey split into latitudinal bands. We found the small scale survey provided a good representation of the statistical distribution of krill densities within its latitudinal band (KS-test, D = 0.048, p-value = 0.98), as well as mean density (t-test p-value = 0.44), but not outside of the band. We recommend further in situ testing of this approach.