Genetic structure in the Amazonian catfish Brachyplatystoma rousseauxii: influence of life history strategies

International audienceThe Dorado or Plateado (Gilded catfish)Brachyplatystoma rousseauxii (Pimelodidae, Siluriformes)is a commercially valuable migratory catfish performingthe largest migration in freshwaters: from the Amazonianheadwaters in the Andean foothills (breeding area) to theAmazon estuary (nursery area). In spite of its importance toinform management and conservation efforts, the geneticvariability of this species has only recently begun to bestudied. The aim of the present work was to determine thepopulation genetic structure of B. rousseauxii in tworegions: the Upper Madera Basin (five locations in theBolivian Amazon) and the Western Amazon Basin (oneregional sample from the Uyucalı´–Napo–Maran˜on–Amazonbasin, Peru). Length polymorphism at nine microsatelliteloci (284 individuals) was used to determine geneticvariability and to identify the most probable panmicticunits (using a Bayesian approach), after a significantdeparture from Hardy–Weinberg equilibrium was observedin the overall dataset (Western Amazon ? Upper Madera).Bayesian analyses revealed at least three clusters inadmixture in the five locations sampled in the BolivianAmazon, whereas only two of these clusters were observedin the Western Amazon. Considering the migratorybehaviour of B. rousseauxii, different life history strategies,including homing, are proposed to explain the cluster distribution.Our results are discussed in the light of thenumerous threats to the species survival in the Maderabasin, in particular dam and reservoir construction