Collection, processing and potential use of sonar data from krill fishing vessels

Omnidirectional sonars (herein sonars) are capable of providing an alternative view of Antarctic krill distribution, and potentially abundance. Data from sonars can be used independently of conventional downward-looking echosounders or as an additional information source as a compliment to existing acoustic surveys. Sonars are capable of sampling large volumes of water and can image entire krill swarms and track changes in swarms through time.  Some commercial krill fishing vessels, e.g.  ‘Juvel’ and ‘Saga Sea', routinely use sonars, and we provide example data and swarm descriptions from these vessels.  The purpose of this paper is to stimulate discussion on the utility of sonars to describe krill within a survey area and to consider the metrics (descriptors) we outline in the paper.  We hope the outcome of our discussions will facilitate the use of sonar data collected from a variety of vessels and sonar types by providing guidance on the operation, sonar system settings, and data analysis techniques.