Deployment and recovery of an archival tag on an Antarctic toothfish in the Ross Sea

Data from electronic archival tags are often used to characterise movement and migration patterns in fishes. Understanding these movement patterns is one of the key information needs for the assessment and management of Antarctic toothfish. We deployed 4 pop-off satellite archival tags on large toothfish on the Ross Sea slope in January 2013 and report on the first recovery of an Antarctic toothfish tagged with an archival tag. The fish was recaptured in the fishery the following season (December 24, 2013), providing 335 days of data archived at 10 min intervals. Summaries of raw data show strong and contrasting patterns throughout the time series in several variables recorded and several periods with distinct behavioural profiles, suggesting significant activity throughout the winter period. With the lack of any daylight signal resulting from constant light or darkness, along with living below the photic zone and under ice, positioning using light-based geolocation is not possible. Current efforts focus on developing a Bayesian modelling approach to fit the most likely movements of the tagged fish during its time at liberty, based on the environmental variables recorded by the tag compared with spatial environmental data on depth, temperature and magnetic field strength.