Patterns in the diet of Illex argentinus (Cephalopoda: Ommastrephidae) from the Falkland Islands jigging fishery

The diet of Illex argentinus was examined using samples collected from the Falkland Islands jigging fishery during February and March 1998. Samples were taken at two hourly intervals from 18:00 to 06:00 h aboard three different vessels. In total, 640 stomachs were examined. The diet of I. argentinus in this study consisted mainly of crustaceans (hyperiid amphipods and euphasiids) with cephalopods (conspecifics) also making up a substantial part of the diet. Fish and gastropods were also preyed upon by I. argentinus, but contributed little to the overall diet. Feeding patterns changed during the course of the night with crustaceans the main prey in the hours before midnight and cephalopods increasing into the morning. The proportion of empty stomachs recorded increased as the night progressed. Although both time and squid length affected the diet composition of I. argentinus, squid length appeared to have a greater impact than time. Crustaceans were most important in the diet of smaller size classes while cannibalism occurred only among the larger squid (>240 mm mantle length).