Investigating the movements and behaviour of Patagonian toothfish (Dissostichus eleginoides Smitt, 1898) around the Falkland Islands using satellite linked archival tags

Knowledge of the seasonal movements of Patagonian toothfish is an essential component for understanding their ecology and fisheries management. As only one demersal longline vessel participates in this fishery in Falkland's waters, over a vast slope area, the use of conventional tags to provide data on migration or stock assessment is not viable. In contrast, archival pop-up tags have enabled the examination of toothfish movements without having to recapture tagged individuals with reasonably high success rates. Patagonian toothfish (n = 30, > 127 cm LT) were tagged with pop-up satellite tags between 19/09/2007 and 7/07/2010 in the South Atlantic close to the Falkland Islands. The data from 16 tags that successfully released and uploaded data (plus one recaptured fish) revealed strong site fidelity, with eleven toothfish moving less than 50 km from their release position over a 6 month period. Furthermore, depth data inferred three behavioural patterns showing seasonal bathymetric movements, foraging and spawning activities. Coinciding with the reported spawning months of July–August, spawning movements were recorded with fish moving repeatedly into shallower waters of 900–1200 m. Foraging behaviours were also evident with differences in the scale of foraging movement related to fish size, possibly linked to a shift in diet with size. Fish were found to move deeper during December and these are potentially post-spawning movements allowing the fish to take advantage of different prey availability.

► First use of archival pop-up tags on a deepwater species, Patagonian toothfish
► Seasonal, feeding and spawning behaviours are revealed.
► Strong site fidelity with most fish moving less than 50 km.