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

摘要

Variations in oceanographic conditions and the distribution of the Patagonian longfin squid Loligo gahi were studied on the southern part of the Falkland Shelf (Southwest Atlantic) during four consecutive austral summers in the period 2000- 2003. The flow of the Falkland Current onto the shelf varied from year to year, both in strength and scale, causing significant variability in the location and resolution of the Transient Zone (a mixing of the Sub-Antarctic superficial waters, which represent the upper layer of the Falkland Current, with shelf waters). Generalised additive models (GAMs) of commercial CPUE data in terms of temperature and, in particular salinity, demonstrated the association of L. gahi with the upper part of the Transient Zone (best identified by salinity in the range 33.9- 33.95). Stronger flows of the Falkland Current onto the western part of the southern Falkland Shelf induced stronger outflows of warmer and less saline shelf waters to the Beauchene Island area, and correspondingly greater offshore movements of squid. Thus, near-bottom salinity on the shelf (which is the best indicator of the position of the Transient Zone) may be a useful predictor of the extents of the distribution of L. gahi aggregations on their feeding grounds.