Abstract
A scattering layer consisting mainly of krill (Meganyctiphanes norvegica) was studied with a submersible transducer, to assess the behaviour of individual organisms in situ by means of split-beam target tracking. Individuals were resolved and tracked, but a rapid increase in average swimming speeds with depth suggested that inaccuracies in the angular estimates affected the estimates. Attempts were made to smooth the tracks during post-processing. Smoothed speeds suggested that most (>78%) invertebrates swam at speeds below 12 cm s–1 (mode ~4 cm s–1), with components of speed larger in the horizontal plane than in the vertical.