Marc Taquet

Fish aggregation device (FAD) research: gaps in current knowledge and future directions for ecological studies

AbstractWe reviewed the literature concerning fish aggregation devices (FADs) to determine areas of relative research deficiency. Using specific searches of the Aquatic Sciences and Fisheries Abstracts (ASFA) database from 1978 to December 2003 and a classical search of the pre-1978 literature, we collected 407 references on FADs. Publications before 1980 were predominantly peer-reviewed, although non-peer reviewed literature has dominated since 1980, due to the numerous technical reports produced as FADs became more widely used in artisinal and large-scale industrial fisheries in the 1980s. Most studies of the ecology of FAD-associated fish were descriptive, with few mensurative experimental studies and even fewer manipulative experimental studies that tested specific hypotheses, due to inherent difficulties in working in the open ocean on objects that are temporary in space and time. Research on the ecology of FAD-associated fish has focused on moored FADs, despite the major FAD-based fisheries being around drifting FADs. Publications presenting information on moored FADs outnumbered papers on drifting FADs by a ratio of 3.5:1. We recommend that greater emphasis be placed by fisheries scientists and funding agencies on researching drifting FADs to provide better information for management of large-scale FAD-based industrial fisheries. Future research should focus on determining the patterns of use of drifting FADs by pelagic species, the underlying sensory processes of attraction and the ecological consequences for individual fish stocks and the wider pelagic ecosystem of the use of FADs as fisheries enhancement tools.

Mechanisms and effects of the aggregation of tuna by Fish Aggregating Devices (FADs)

The associative behaviour of large pelagic fish, tuna and related species, is strongly influenced by the presence of fixed or drifting, natural or artificial floating objects such as FADs. The number of FAD for the development or maintenance of tuna fisheries, both oceanic industrial and small coastal fisheries, is increasing in such a way that at present one quarter of the worldwide production of tuna (one out of four million tons produced annually) is dependent upon the use of FAD. This evolution is, in some respects, worrying and has justified holding an international meeting on the theme “Tuna fishing and FAD”. This symposium took place in October 1999 at La Martinique (French West Indies). It follows an international working group organized by the IATTC in Jolla (California) in 1996 (Scott et al., 1999). The papers presented during the symposium are published in two different publications: – Proceedings “Les Actes de Colloques” (Le Gall et al., 2000) bring together regional summaries (Pacific, Atlantic and Indian oceans and Mediterranean sea), questions relating to the technology of FAD and associated fishing techniques, the behaviour of tuna towards fishing detection equipment, the impact of FAD on the behaviour of fishermen; – This special issue of the journal Aquatic Living Resources: Mechanisms and effects of the aggregation of tuna by Fish Aggregating Devices (FADs), attempts to provide some understanding of the determinism of the association between attracting objects and large pelagic fish, to propose a model of tuna movement, to describe the preferential distribution of species and size of aggregated fish, to compare the specific duration of residence in the different types of aggregation (FAD, sea mounts, etc.). The need to conduct research programs on an international level in order to progress in the understanding of this phenomenon has been emphasized. What is the role of FAD in the oceanic environment: refuge from predators, concentration of food, signs of rich environment, points of spatial reference and orientation support, meeting point (Fréon and Dagorn, 2000)? Amongst the hypotheses developed to explain the aggregation of pelagic fish on FAD, some have been the subject of presentations and discussions concerning the experimental designs already implemented or which will serve as the basis for future scientific investigations. The main research presented in this special issue deals with: – the changes in associative behaviour of tuna in relation to FAD through the joint use of underwater acoustic prospecting (echo sounders, sonar) and detecting by ultrasonic devices; – the analysis and model building of movement and migration surrounding FAD networks and of exchanges between offshore areas and coastal fisheries; – the effects of FADs on the ecology of tuna, and in particular the alteration of their place in the food chain system caused by FADs; – the impact of changes in the means of operation on production in specific tuna fisheries in terms of size levels and species diversity; – the organisation and emergence of industrial and local networks, and their effect on the marketing of fish products.