Trophic analysis and fishing simulation of the biggest Amazonian catfish

Abstract

Currently, it is unanimous the fact that the ecosystem approach gives important insights to support fisheries
stock assessment and management and healthy sustain aquatic ecosystems. This work aims at the
quantification of energy flows at várzea (Amazon floodplain) and the simulation of increase in the fishing effort
regarding the biggest predators, the catfish, and decrease of flooded forest cover. It was used the Ecopath with
Ecosim software to build BAGRES model, which could allow inferences on ecosystem stability. Results showed
that: i) BAGRES model has high overhead (69.7%) and Production/Respiration rate very close to 1, showing that
this floodplain system is sufficiently mature and capable to support disturbance; ii) Finn’s cycling index for
BAGRES (14.6%) is high when compared to other worldwide system; iii) increasing the effort of the catch of
three species of Brachyplatystoma (catfish) have positive effects on biomass and consequently catch and
landing of their main preys; iv) in the simulation of deforestation of Floodplain Forest (with no natural
regeneration), all species are prejudiced (no exception), including Brachyplatystoma groups that do not use
flooded environment. Therefore, the indirect consequence of the deforestation is more intense over fish stocks
than increasing fishing effort. The BAGRES model results have important implications for the current policymaking for inland fishing in Brazil, currently mostly based on “defeso” (fishing restriction season), suggesting
the necessity of incorporate the impacts which drive the deforestation in Amazon Floodplain.