Migratory Movements of Large Catfish in the Xingu River (Amazon) Revealed By Combined Acoustic and Radio Telemetry

The Amazon basin is home to a large number of migratory fishes whose behavior is still poorly known. Historical fisheries catch data suggest that critical habitats of large migratory catfish are often separated by hundreds of kilometers. We used acoustic (fixed) and radio (fixed and mobile) telemetry to investigate migratory movements of redtail (Phractocephalus hemioliopterus) and surubim (Pseudoplatystoma spp.) catfish along a 700-rkm stretch of the Xingu River. Fish were tagged and released downstream (62 redtail and 36 surubim) and upstream (47 redtail and 13 surubim) of a long stretch of rapids (known as the “Big Bend”) located in the lower river that is considered a natural barrier to upstream fish migrations. Only tagged surubim (n=4) moved upstream of the rapids, whereas movements downstream of the rapids were not detected for either species. Thirteen redtail and five surubim catfish moved >50rkm upstream (56—329rkm) of the release sites at the end or beginning of the floods. These findings suggest the Xingu River rapids are not a barrier to the upstream migration of surubim and that both species migrate upstream to distant habitats during the floods (presumably for spawning).