Initial results of satellite linked archival tagging in the Patagonian toothfish (Dissostichus eleginoides Smitt, 1898) around the Falkland Islands

No abstracts are to be cited without prior reference to the author.

Understanding the movements of Patagonian toothfish is an essential component of their 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 and 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 reasonability high success rates. A total of 16 toothfish >132cm LT were tagged between 19/09/2007 and 7/08/2009 on the northeastern part of the Falkland Islands’ slope and northern and eastern slopes of the Burdwood Bank. The data from 9 tags that successfully released and uploaded data contradicted a hypothesis concerning the extent of migrations between their spawning and feeding grounds. Instead, the data revealed strong site fidelity, with five toothfish moving less than 50km from their release position over a 6 month period. In addition four individuals were found to move 100km or more from the south of the Burdwood Bank to the north of the bank or out towards the Scotia Ridge and one individual moved 126km north-westwards on the feeding grounds. Furthermore, our data revealed that toothfish undertake vertical migrations with movements ranging between 8 – 584m over six hourly periods. During the Austral summer three fish moved into deeper waters and one of these returned to shallower waters during the following autumn. The results of these data have made it necessary for us to reexamine the spawning behaviour of toothfish in the south Atlantic