Population dynamics of the migratory fish Prochilodus lineatus in a neotropical river: the relationships with river discharge, flood pulse, El Ni?o and fluvial megafan behaviour

摘要

The relative importance of flood pulse dynamics and megafan behaviour for the Sábalo (Prochilodus lineatus) catches in the neotropical Pilcomayo River is studied. The Sábalo catches can mainly be explained by decreased river discharges in the preceding years resulting in smaller inundated areas during rainy season floods and thereby in a decreased area of feeding grounds for the fishes. The decreased river discharges and the related decline of Sábalo catches in the 1990's can be linked to the 90-95 El Ni?o event. In 2007 the Sábalo catches were comparable to the catches before the "El Ni?o" event. The connectivity (continuity) between the main river and flood plain areas, which is influenced by sedimentation processes, is also of great importance and very probably plays a more important role since the late 1990's.