A network approach to by-catch in a multi-species Mediterranean small-scale fishery

Fisheries management has been traditionally focused on resource-based approaches that underscore the interaction between the sociological - e.g., fishermen behavior reflected in spatial allocation of fishing effort and gear choice - and the ecological component of the system. In this line, the network analysis offers valuable tools that allow the integration of both components, identifying emergent properties resulting from their interactions-e.g., management units. Specifically, modularity refers to the degree to which some individuals in a group or module have a higher probability of mutual connection than individuals in others groups. Compared to previous approaches in fisheries, modularity allows identifying discrete management units without subjectivity in the delimitation of groups (number and size). Herein, we represent the by-catch in the small-scale fishery (SSF) of Palamós (Catalonya, Spain) as a bipartite-network where nodes correspond to fishing events (152) and species (125), and links indicate the relationship among them. We identified nine modules composed by different combinations of catch composition, fishing areas, and fishing gears. Although they could resemble fishing tactics or mètiers, herein we suggest that modules as defined here could be considered management units not evident from other techniques. Finally, we stress the potential of modularity analysis in the definition of marine fish stocks and management units.