Tracking arrow squid movements with an automated acoustic telemetry system

Abstract

This study investigated the movement, spatial usage and activity patterns of the arrow squid Nototodarus gouldi (Cephalopoda: Ommastrephidae) using an automated acoustic telemetry system. Sixty-four automated acoustic receivers were aligned as underwater 'curtains' across the entrances to bays and inlets around Storm Bay, southeastern Tasmania. N. gouldi were tagged with small uniquely coded transmitters and released. Twelve tagged squid were detected for up to 37 d over an area of more than 300 km2. Tagged squid moved widely between Storm Bay and the Derwent River, but none were detected moving into the adjoining bays or the D'Entrecasteaux Channel. Tagged squid appeared to move out of Storm Bay throughout the study period, suggesting a highly dynamic population. There was evidence of a relationship between level of activity and photoperiod, with visits to receivers being longer and more variable in duration in the night compared to the daytime. Schooling or group movement was not observed. Rates of movement between non-adjacent receivers varied widely with those over distances of 10 km or more, ranging from 0.09 to 0.52 mantle lengths per second (ML s-1), and 1 instance of an average speed of 3.6 ML s-1 over 9.3 km.