Does social behavior influence the dynamics of aggregations formed by tropical tunas around floating objects? An experimental approach
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Tropical tus associate with objects floating at the surface of the ocean, a behavior widely exploited by fish- ers. However, the respective roles played by environmental variables and behavioral processes (e.g., social behavior) in the formation of these aggregations remain elusive. To investigate the role of social behavior in the dymics of such aggregations, we used the biry choice approach. The experimental design com- prised two close and identical anchored fish aggregating devices (FADs) eq uipped with an echo sounder buoy to monitor the aggregated biomass of tu under each device. Alysis of the results entailed character- izing whether the aggregated biomass is distributed asymmetrically (indicative of social behavior playing a role in the dymics) or symmetrically between the two close and identical FADs, and comparing the results with theoretical distributions based on different definitions of basic units (individual fish or small schools). The results suggest that social interact ions underlie aggregation processes, which represents a major advance in our understanding of these aggregations, a priority for science-based fishery magement. While recogniz- ing the logistical and technical constraints, we encourage the development of experimental studies (e.g., in which animals are presented with controlled situations) to enhance our understanding of the behavior of large pelagic fish.