INTERACTIONS BETWEEN OCEANOGRAPHY, ECOLOGY AND FISHERY BIOLOGY OF THEOMMASTREPHID-SQUID MARTIALIA HYADESI IN THE SOUTH ATLANTIC

The seven star flying squid Martialia hyadesi is an oceanic slope omma strephid with a circumpolar distribution associated with the Antarctic Polar Frontal Zone (APFZ) and is a minor, variable catch in the South Atlantic Illex argentinus fishery. There have been occasional unusual ly large catches of M, hyadesi, the latest being in 1995. Because of t he importance of understanding the influence of the physical environme nt on fisheries for oceanic squid, and interest in developing a new fi shery for id, hyadesi in the CCAMLR area, we examined specimens and da ta from the 1995 season and analysed 10 yr fisheries and remotely sens ed oceanographic data sets from the area. The 1995 data show that M, h yadesi remains in the cool APFZ waters of the Falkland Current where i t preys on oceanic fish and crustaceans and its distribution rarely ex tends over the Patagonian Shelf. The squid exploited by the fishery in 1995 were 6 to 12 mo old; females were immature but some males were f ully mature. A remotely sensed sea surface temperature (SST) image rev ealed mesoscale features at the shelf break front between Patagonian S helf water and APFZ water where the squid were caught. The appearance of M, hyadesi in the fishery over the last decade, including 1995, has been related to SST anomalies. Teleconnections probably exist between these anomalies, El Nino/Southern Oscillation (ENSO) events in the Pa cific and sub-decadal oceanographic instability in the Antarctic. Squi d are short-lived and populations are Likely to be able to respond rap idly to environmental change. However, it is not clear at what stage i n the life cycle of M. hyadesi these oceanographic events exert their effect. We propose 2 alternative, but not mutually exclusive, hypothes es. Warm events prior to the appearance of M, hyadesi may favour repro ductive success of the parent generation giving rise to a strong recru itment, or alternatively this cool water species may extend its range to the edge of the Patagonian Shelf early in the development of cold o ceanographic events. In either case oceanographic effects are probably mediated via the squid's prey.