Euphausiid assemblages in and around a developing anticyclonic Leeuwin Current eddy in the south east Indian Ocean

The composition, distribution and abundance of euphausiids in and around an anticyclonic eddy of the Leeuwin Current were investigated in the south-east Indian Ocean off Western Australia (31 °-34°S). In total, 22 euphausiid species were identified, two of which, Euphausia sanzoi and Thysanopoda astylata, are new records for the south-east Indian Ocean. In addition, five species represent new records for Australian EEZ waters and seven are new records for the latitude of the eddy field. Euphausia recurva and Stylocheiron carinatum were the most abundant species in the Leeuwin Current and eddy perimeter, reaching mean abundances of 135.5 ± 22.3 m-2 and 70.5 ± 12.2 m-2, respectively. Pseudeuphausia latifrons was the most abundant species over the shelf (52.1 ± 14.0 m-2). Species richness was greater in the eddy and surrounding oceanic waters (18-20 species) than on the adjacent shelf (11 species). Of the water column properties included in a multivariate multiple regression analysis, only depth made a significant contribution to explaining the variation in euphausiid assemblages, probably due to mixing of water masses in the developing eddy. This study has revealed the influence of mixing processes associated with a Leeuwin Current eddy on holoplanktonic euphausiids in the south-east Indian Ocean.