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In this study, we consider the influence of mesoscale oceanographic processes around the Falkland Islands (Islas Malvinas) in the South-west Atlantic, during the period in which the commercial squid fishery for Illex argentinus operates. Spatially referenced fishery data and satellite-derived advanced very high resolution radiometry (AVHRR) sea surface temperature (SST) data were examined using geographic information system (GIS) techniques. The distribution and relative abundance of I. argentinus in the Falkland Islands fishery was examined for the period 1989-96. Three consistent areas of high abundance were observed to the north-east (shelf-break region) and north-west (shelf region) of the islands, and close to the northern coast of East Falkland. Areas of high sea surface temperature gradients (thermal gradients) extracted from remotely sensed satellite images were used as an indicator of mesoscale oceanographic activity and compared with the location of the fishery. I. argentinus were found to be associated with areas of thermal gradients, commonly seen at the interface of Falkland Current and Patagonian shelf waters. The techniques used in this analysis allow the overlay and analysis of physical oceanographic and fishery data with potential applications in fisheries management and operational fisheries oceanography.

Interannual variability in the mesoscale oceanography of the inferred hatching area of winter-spawned Illex argentinus (i.e. those belonging to the Southern Patagonic Stock) was examined during the hatching months of June and July. The hatching area was defined as the region 32°–39°S, 49°–61° W, and indicators of the surface oceanography in this area were derived from remotely sensed advanced very high resolution radiometer (AVHRR) sea-surface temperature (SST) data. Interannual variability in the mesoscale oceanic circulation in the inferred hatching area was examined in terms of (1) the area occupied by "frontal" waters (defined as areas with SST gradients of ≥3°C over an area of 15 km by 15 km), and (2) the area occupied by waters of "favourable" SST (defined as those with temperatures in the range 16–18°C). Oceanographic indicators were compared with an index of I. argentinus recruitment to the Falkland Islands (Malvinas) fishery (catch per licensed vessel) for the period 1987 to 1999. The two oceanographic indicators were seen to co-vary, with a decrease in the proportion of the inferred hatching area occupied by frontal waters corresponding to an increase in the proportion of water of favourable SST. High squid abundance was found to be associated with a lower proportion of frontal waters or a higher proportion of favourable-SST waters within the inferred hatching area in the year preceding the fishery. Interannual variability in the interaction of the Brazil and Falkland Currents in the inferred hatching area during the early life stages is shown to be important in influencing the population size of I, argentinus, and mechanisms influencing squid recruitment in this highly dynamic region are discussed.