Analysis of the spatio-temporal pattern of Southern blue whiting (Micromesistius australis australis) abundance in the bottom-trawl fisheries in the southwest Atlantic using GIS techniques

Abstract

Southern blue whiting (Micromesistius australis australis ) inhabits the waters of the Southern Hemisphere, and in the south-west Atlantic Ocean. It is distributed over an area next to the Falkland/Malvinas Islands, where it is commonly the most abundant commercial finfish species. This fish migrates to the outer Falkland shelf and aggregates in dense schools to spawn in August-September in the south-western part of the islands. Feeding concentrations of Southern blue whiting are targeted by specialized surimi vessels until the following March. Southern blue whiting is also taken as an occasional bycatch by finfish trawlers. Fishery and biological information collected by scientific observers aboard commercial Spanish trawlers between 1988 and 2003 were analysed in relation to physical and environmental factors to establish the spatio-temporal pattern of the species. The data included 26 168 commercial hauls of which 4 797 positive (including effort, catches and discards, as well as biological and environmental information). CPUE (Catch Per Unit Effort, kg⋅hr-1) was used as abundance index. The analysis of the general spatio-temporal pattern of fish abundance, and the influence of environmental factors, such as SST, SBT and depth on fish abundance and distribution, was based on correlation, variograms, and time-series maps created using GIS. Mature individuals and more specifically spawning females were recorded mainly in the waters south and south-west of the Islands, between 100 and 200 m isobaths.