Modelling growth of Antarctic krill: growth trends with sex, length, season, and region

Growth trends of Antarctic krill with sex, length, season and region using over 10 years accumulation of instantaneous growth rate (IGR) measurements were modelled using a Linear Mixed Model (LMM). A model of inter-moult period (IMP) as a function of temperature, required to convert IGR to specific growth rate, was fitted to data from published constant-temperature rearing studies and this model was used to predict seasonal IMP using a model of the average sea-surface temperature seasonal trend for each region. Smaller krill exhibited higher growth rates and a progressive decrease in the IGR with increasing size was generally observed. This trend decreased from summer to autumn with small to negative values of IGR predominating across all size classes by autumn. The period of rapid growth was December in Indian sector, whereas in the Scotia Sea sector it appeared to be a few months earlier than this. Significantly lower growth rates were exhibited by females in January and February relative to males. Seasonal specific growth rates estimated in this study were compared to previous studies, and suggested that wild krill show more rapid growth over a shorter growth period than it was traditionally thought.