Integrating fishermen knowledge and scientific analysis to assess changes in fish diversity and food web structure

In this paper the Ecosystem Approach to Fisheries (EAF) and the Fishermen Knowledge Approach (FKA) were applied to understand changes in a tropical coastal lagoon. Then, the fishermen experience-based knowledge, literature information and data sampling were combined aiming to understand biodiversity loss and food web changing in their fishing environment exposed to the introduction of an invasive fish species. Fishermen indicated the changes in fish species composition and simplification in trophic web, confirming biological data. However they do not attributed changes to the species introduction (our ecological hypothesis previously assumed), but to the sequential construction of bridges that interrupted water flow between the lagoon and the ocean (their environmental hypothesis). This assertion fitted to Ecopath model simulations outputs in which exotic species removal from the ecosystem does not recovery fish composition or the trophic web complexity. Fishermen recalled as larger as smaller species, the matching between food web described by fishermen and the food web from literature and the justification for biodiversity loss presented by fishermen, broadened the confidence on their role as experts. This approach merged the historical views of fishermen and provided evidence on the value of complement scientific data with experts consulting.