Arrow squid: stock variability, fishing techniques, trophic linkages - facing the challenges

This work focused on the key fishing region off Portland as well as the Great Australian Bight where a pelagic trawl fishery for arrow squid is proposed. The outcomes of this research provided a detailed understanding of the relationship between arrow squid populations and environmental conditions. This was achieved through detailed modelling using both biological and oceanographic/environmental parameters. Due to seasonality in upwelling and nutrient loads, and primary production blooms, arrow squid are subject to large variability in environmental conditions over small spatial and temporal scales. The influence of these oceanographic processes, quantified through satellite image derived data (e.g. sea surface temperature), revealed how arrow squid respond to environmental conditions in terms of recruitment, growth and reproduction. Growth and recruitment were determined through ageing of squid samples using statoliths and back-calculation of hatch dates. It was not only of interest to describe how squid respond to oceanographic changes through growth, reproduction and recruitment, but how these changes influence the availability of prey. Squid dietary analyses were also conducted in association with a biochemical analysis of squid tissue to determine squid condition. An ecosystem model was developed to facilitate understanding of stock dynamics, and to determine the influences that both natural and fishery induced changes have on stock size. Results from this research will help fishery management facilitate the optimal use of the arrow squid resource through the development of an ecologically sustainable fishery.