Fishing sustainability via inclusion of man in predator–prey models: A case study in Lago Preto, Manacapuru, Amazonas

We modeled a fisheryʹs system with two types of fishermen, commercial and subsistence fishermen, who exploit the fish stock at the Amazonian floodplain lakes. In the first model, we combined the Lotka–Volterra equations with Verhulstʹs Logistic model, by inserting hydrological cycle oscillations. The second model was based on the equations proposed by Berryman, which reflect the predatorʹs functional response in relation to the preyʹs population behavior, taking into account the hydrological cycle. In both models, commercial fishermen and local direct consumers (called riverside dwellers – riverines – in the model), were considered the only predators acting upon fishing stocks. Primary data were collected in 48 riverside homes throughout 2006. The total number of interviewees corresponds to 69.6% of the universe of homes in the community defined as study area. The riverines were the predators that showed capacity to eliminate the opponent predators (commercial fishermen). The best scenery obtained regarding the number of prey, was the one that showed only commercial fishermen in the region. On the other hand, the simulations show that the coexistence is possible among predators, and between predators and their prey. The seasonal model with functional response provides a better response in relation to the systemʹs current situation and to the established modeling conditions than the Lotka–Volterra seasonal model. The seasonal model with functional response also showed a better response pattern in all scenarios, with oscillations taking place more gradually, both for variations associated with the flooding pulse and for relations between predators and prey.