Density and distribution of euphausiid larvae in the Scotia Sea in the 2011 summer

Abstract

Monitoring of early euphausiid larvae provides valuable information on the mechanisms involved in recruitment to the adult populations. As the Antarctic is undergoing rapid environmental change, these mechanisms are key to ecosystem-based management of the krill fishery. We analyzed the distribution and abundance of early euphausiid larvae (calyptopes I to late furciliae) from 76 plankton samples from surface to 300 m depth in the Atlantic sector in January 2011 in relation with a previous survey and published information. Thysanoessa macrura (mean density: 209 ind m−2) dominated the sampling while Euphausia superba (mean density: 13.63 ind m−2) and Euphausia frigida (mean density: 10.05 ind m−2) were also present. T. macrura density increased while E. superba experienced a high decrease respect to historical data. Clustering of stations and correspondence analysis showed that the associations of larvae and water masses are in agreement with literature reports, so the differences on the abundance of early larvae are within the observed variability and cannot be attributed to any single factor, suggesting that it is due to more subtle changes such as the stability of the water column and/or vorticity in the fronts.