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 km2) 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
km2) 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.
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)
Document Number:
WG-ASAM-2023/P01
Submitted By:
Dr Martin Cox (Australia)
Approved By:
Dr Philippe Ziegler (Australia)
Agenda Item(s)
Publication:
PLOS ONE, 17(8): e0271078 (2022), doi: https://doi.org/10.1371/journal.pone.0271078
Abstract