Ecology, Growth, and Migration of Pseudoplatystoma fasciatum in the Amazon Basin

Freshwater fishes include diverse lineages collectively summing to over 18,000 species, representing ~51% of all fishes and ~25% of all vertebrates. About one-third of all freshwater species occur in the Neotropics, with an estimated 4,475 species within 71 families. Catfishes of the Order Siluriformes include 39 families with 498 accepted genera and 4,123 species. More specifically, members of the Family Pimelodidae, the long-whiskered catfishes, and the genus Pseudoplatystoma are distributed from South America to southernmost Mexico. The family Pimelodidae includes 30 genera and 116 described species. Fishes of the genus Pseudoplatystoma support important commercial and artisanal fisheries, and some species have become important to regional aquaculture. Most species of the genus are under pressure by dam construction and overfishing. Pseudoplatystoma fasciatum is a catfish species that transports nutrients and connects habitats through migration. It is also a source of food security and income for riverine people in the Amazon basin. This species is heavily fished and may be threatened by the growing construction of hydropower dams. One ecological aspect lacking in the literature is how the growth of Pseudoplatystoma species is affected by interannual variations in the flood pulse. Another crucial aspect of fish ecology is migration. In this dissertation, I review the ecology and conservation of the genus Pseudoplatystoma. Then, I evaluated how inter-annual hydrological variations within the Amazon basin influence the growth of the catfish P. fasciatum. Finally, I used otolith microchemistry to understand the migration ecology of P. fasciatum in the Amazon Basin. I found an inverse relationship between increment width in fish hard parts and hydrological indices. I also found that growth of P. fasciatum was no different in years with intense and mild floods across age-classes 1-5, although different for age-class 6. However, the growth of P. fasciatum was faster in years of mild droughts for all age-classes. I found that thirty-four percent of all fish analyzed migrated between rivers with different Sr signatures, and 66% did not. Also, eighty percent of all fish migrated between rivers with the same type of water (i.e., white-water and black-water rivers), while only 10% migrated between different water types. The mean migration distance migrated was 126 km, with most specimens migrating between 72 and 237 km. I also found that no fish of age one or age six or older migrated. My results on the migratory ecology of P. fasciatum allow me to put forward two main implications for the sustainable management of its fisheries and species conservation. The growth of P. fasciatum can be affected by construction and operation of hydropower dams, climate change, and fisheries. With continued research and collaboration among research groups, understanding the biology and ecology of this genus would fill these knowledge gaps and contribute to fisheries management and conservation of the eight species of the genus Pseudoplatystoma. These actions would contribute to regional ecological and economic sustainability.