Aida Campos

Automatic analysis of deep-water remotely operated vehicle footage for estimation of Norway lobster abundance

Underwater imaging is being used increasingly by marine biologists as a means to assess the abundance of marine resources and their biodiversity. Previously, we developed the first automatic approach for estimating the abundance of Norway lobsters and counting their burrows in video sequences captured using a monochrome camera mounted on trawling gear. In this paper, an alternative framework is proposed and tested using deep-water video sequences acquired via a remotely operated vehicle. The proposed framework consists of four modules: (1) preprocessing, (2) object detection and classification, (3) object-tracking, and (4) quantification. Encouraging results were obtained from available test videos for the automatic video-based abundance estimation in comparison with manual counts by human experts (ground truth). For the available test set, the proposed system achieved 100% precision and recall for lobster counting, and around 83% precision and recall for burrow detection.

VMS-based fishing effort and population demographics for the European squid ( Loligo vulgaris ) off the Portuguese coast

This study presents a 1-year synopsis of the trawl fishery for the European squid Loligo vulgaris in Portuguese waters, integrating length-structured landings with corresponding geo-referenced fishing activities. From vessel monitoring system (VMS) data, landings and biological sampling, a “status-report” was obtained for 2003. Fishing pressure was found to be most intense in inshore areas of the northwest and the south coasts. Population size structure, classified into three categories, was not uniform throughout the fishing areas. Larger squid are found offshore in the northwest (International Council for the Exploration of the Sea—ICES rectangle 10E0) and in the south (rectangles 2E1 and 3E1), whereas all inshore western coast rectangles showed larger proportions of small squid relative to the southern rectangles. The analysis carried out in this study provides an insight into the possible impact of the fishing intensity pattern on the population structure in various zones. The results demonstrate the benefits of combining geo-referenced fisheries information with landings and size data, to produce explicit spatio-temporal information that can contribute to integrated planning and management for the sustainable exploitation of this resource.