The effect of Falkland Current inflows on offshore ontogenetic migrations of the squid Loligo gahi on the southern shelf of the Falkland Islands

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

After reaching the continental slope to the south of the Falkland Islands (South Atlantic Ocean), the northern branch of the Antarctic Circumpolar Current splits into two main northward flowing streams negotiating the Islands from the west (weaker Patagonian Current) and east (stronger Falkland Current). The Falkland Current meets the slope near Beauchene Island causing a strong upwelling of the Subantarctic Superficial Water mass and flows up onto the shelf mixing with the Shelf Water mass and producing a Transient Zone (TZ) rich of nutrients. Every austral summer juveniles of the Patagonian longfin squid Loligo gahi migrate from their nearshore spawning and nursery grounds and aggregate near the bottom of their offshore feeding grounds which are closely associated with the inshore boundary of TZ. Three complex oceanographic and biological surveys were made in the period of the beginning of squid offshore migrations in February 2000-2002. It was found that the shelf inflows of the Falkland Current varied from year to year both in strength and scale, causing significant variability in the location and resolution of the transient zone. Both the starting time of offshore migrations and the spatial distribution of feeding aggregations of L. gahi also varied in these three years. Possible correlations between the distribution of different oceanographic parameters, including the position of TZ, with the distribution of L. gahi were analysed, and their implication for fishery management were discussed.