Improving the accuracy of krill target strength using a shape catalog
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Antarctic krill are subject to precautionary catch limits, based on biomass estimates, to ensure human activities do not adversely impact their important ecological role. Accurate target strength models of individual krill underpin biomass estimates. These models are scaled using measured and estimated distributions of length and orientation. However, while the length distribution of a krill swarm is accessible from net samples, there is currently limited consensus on the method for estimating krill orientation distribution. This leads to a limiting factor in biomass calculations. In this work, we consider geometric shape as a variable in target strength calculations and describe a practical method for generating a catalog of krill shapes. A catalog of shapes produces a more variable target strength response than an equivalent population of a scaled generic shape. Furthermore, using a shape catalog has the greatest impact on backscattering cross-section (linearized target strength) where the dominant scattering mechanism is mie scattering, irrespective of orientation distribution weighting. We suggest that shape distributions should be used in addition to length and orientation distributions to improve the accuracy of krill biomass estimates.
Bairstow , F J , Gastauer , S , Finley , L , Edwards , T , Brown , C T A , Kawaguchi , S & Cox , M 2021 , ' Improving the accuracy of krill target strength using a shape catalog ' , Frontiers in Marine Science , vol. 8 , 658384 . https://doi.org/10.3389/fmars.2021.658384
Frontiers in Marine Science
Copyright © 2021 Bairstow, Gastauer, Finley, Edwards, Brown, Kawaguchi and Cox. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
DescriptionFB was funded by an EPSRC studentship (grant code: EP/R513337/1). SG received financial support from the Gordon and Betty Moore Foundation.
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