Nas últimas décadas, reservatórios de hidrelétricas do Brasil foram estocados com centenas de milhões de jovens peixes migradores, mas quase nenhuma pesquisa sobre a estocagem foi conduzida. Para estudo da estocagem, etiquetar os peixes a serem estocados é essencial. Neste estudo, nós determinamos a mortalidade devido ao manejo, taxa de retenção da marca e taxa de crescimento absoluto de juvenis de curimbatá de cativeiro (Prochilodus lineatus) marcados com 'coded wire tag' (CWT), etiqueta amplamente utilizada em peixes estocados. Nós injetamos o CWT na musculatura dorsal logo abaixo do primeiro raio da nadadeira dorsal. Apesar de exigir manutenção frequente do injetor de CWT, esse local mostrou ser apropriado para a marcação de jovens de curimbatá. Não houve mortalidade de curto prazo nos juvenis manejados para marcação com CWT, a taxa de retenção do CWT foi elevada (≥ 98,2%), mesmo após 174 dias da marcação. Além disso, o CWT não influenciou na taxa de crescimento absoluto dos peixes etiquetados. O CWT mostrou ser efetivo para marcar juvenis de curimbatá, e acreditamos que ele também o será para muitas outras espécies de peixes brasileiros utilizadas em estocagem.

In recent decades, Brazilian hydroelectric reservoirs have been stocked with hundreds of millions of juvenile migratory fish, but almost no research on stocking has been conducted. In order to study stocking it is essential to tag the fish to be stocked. In this investigation we determined handling-induced mortality, tag retention rate, and absolute growth rate of hatchery-reared juvenile curimbatá (Prochilodus lineatus) tagged with coded wire tags (CWT), a tag widely used on stocked fish. We injected CWT into the dorsal musculature just below the first dorsal fin ray. Despite the need for frequent tag injector maintenance, this tagging location proved to be suitable for tagging juvenile curimbatá. We found no short-term mortality of juvenile curimbatá handled for CWT tagging, high retention rate for CWT (≥ 98.2%) even after 174 d of tagging, and no influence on absolute growth rate by CWT. We conclude that CWT is effective at tagging juvenile curimbatá, and we expect that it will also be effective for many other Brazilian fish species used for stocking.

In the Rio Doce basin of southeastern Brazil, the freshwater fish Hoplias malabaricus (trahira) is a widespread predatory characin and one of the few resilient native fishes in a highly impacted lake system. In order to test for genetic differentiation in populations within this basin and for biogeographic relationships among populations of this species in other basins, a study was conducted using RAPD-PCR analysis of Rio Doce samples (N = 63) and phylogeographic analyses with mitochondrial DNA (mtDNA) haplotypes, including the Rio Grande and Macacu river basins. In the Rio Doce basin, the patterns of genetic similarity of RAPD-PCR markers (individual fingerprinting and Nei’s genetic distance) suggest the existence of two genetically different groups, one composed of the lacustrine populations Carioca and Dom Helvécio, and the other of riverine and the remaining lacustrine populations. The differences in the RAPD-PCR patterns may be explained by the existence of sub-basins within this lacustrine system. A maximum parsimony tree of cytochrome b fragment (383 base pairs) supports the view that trahiras of the Rio Doce share a complex biogeographic history with those of neighboring basins. The phylogeographic patterns may be explained by a common history of the watersheds of the Rio Doce, Paraíba do Sul, and Rio Grande basins, corroborating the hypothesis of a Plio-Pleistocene separation of these drainage systems, forming the Mantiqueira "divortium aquarium".