Hybrids between Pseudoplatystoma corruscans and P. reticulatum (Siluriformes: Pimelodidae) previously reported in the Upper Paraná River are likely escapes from aquaculture farms: evidence from microsatellite markers

ABSTRACT The production of hybrids of the 'pintado', Pseudoplatystoma corruscans (Spix & Agassiz, 1829) and 'cachara', Pseudoplatystoma reticulatum (Eigenmann & Eigenmann, 1889) in captivity has generated many concerns about the possibility of introduction of farmed hybrids into natural environments. In the last decade, hybrids between these species, known as 'pintachara' or 'cachapinta', were reported from different regions of the Upper Paraná River basin. Prospection of these hybrids is important in order to orient conservation programs for the species involved. Knowledge of the presence of these hybrids will direct conservation strategies towards prevention and/or mitigation of the effects of cross breeding in natural populations of P. corruscans (the native species of the genus) and farmed hybrids. In this study, surveyed the larval population using molecular tools to detect the presence and assess the origin (natural hybridization or escapes from fish farms) of hybrids in natural water bodies. Nine microsatellite markers were used to detect signals of hybridization and introgression of P. reticulatum in larvae and adults of P. corruscans in Upper Paraná River basin, between Itaipu Dam and Porto Primavera Dam. The specimens were sampled in the Upper Paraná channel and in tributaries where hybrids had been detected in the past, during two reproductive seasons. Despite of that, no sign of hybridization and introgression was found in the 171 larvae and 75 adults sampled, suggesting that the specimens detected in previous studies had originated from escapes of aquaculture farms

Dynamics of fish larvae recruitment in the hydrographic basin of the Paraguay River in western Brazil

Abstract The conservation of fish assemblages depends on the longitudinal and lateral connectivity between riverine habitats, in particular during the breeding season and the initial development. This study investigated the composition and spatio-temporal structure in the ichthyoplankton of the hydrographic basin of the Paraguay River in western Brazil to identify the local spawning grounds and the importance of the longitudinal connectivity of economically valuable migratory species. Data were collected at 10 sites between two breeding seasons (2017/2018 and 2018/2019). Were collected 8,635 larvae, representing 55 taxa in 25 families, including the migratory species Brycon hilarii, Hemisorubim platyrhynchos, Piaractus mesopotamicus, Prochilodus lineatus, Pseudoplatystoma spp., Salminus brasiliensis, Sorubim lima, and Zungaro jahu, which are important fishery resources, with the highest larval densities being recorded between November and January. The Sepotuba, Paraguay, Jauru, and Cabaçal rivers were the areas of greatest connectance, and should thus be considered critical for the conservation of the longitudinal connectivity of this fluvial system, indicating that the migratory species spawn upriver. More efficient fisheries management mechanisms are needed, respecting the spawning period of migratory species, maintaining quality and longitudinal connectivity between habitats, and characteristics necessary for successful larval recruitment

Mudanças ontogênicas no trato digestório e dieta de Apareiodon affinis (Steindachner, 1879) (Osteichthyes, Parodontidae) - DOI: 10.4025/actascibiolsci.v26i3.1542

Feeding aspects of Apareiodon affinis larvae and juveniles are described in this work. Samples collected by plankton net were taken from February, 1991 to February, 1992 in Ressaco do Leopoldo, Paraná River. The mouth is small and terminal in preflexion and flexion larvae and inferior at the end of this development period and in juveniles. The digestive tract is simple and straight in preflexion larvae, but different in those in postflexion. The diet was basically algae, characterizing this species as algivorous during all its development. The analysis of the digestibility did not show the preferential time of feeding of the different development stages. This was probably because of the sampling type utilized and because of the food consumed by the individualsAspectos da alimentação de larvas e juvenis de Apareiodon affinis são descritos. As amostragens foram realizadas no Ressaco do Leopoldo, alto rio Paraná, entre fevereiro de 1991 e fevereiro de 1992, utilizando rede de plâncton. Nas larvas em pré-flexão e flexão, a boca é pequena e terminal, passando a inferior no estágio de pós-flexão e nos juvenis. O tubo digestivo é simples e reto nas larvas em pré-flexão e diferenciado naquelas em pós-flexão. A dieta foi constituída principalmente por algas, caracterizando essa espécie como algívora durante todo o seu desenvolvimento. A análise da digestibilidade não evidenciou o horário preferencial de alimentação dos difirentes estágios de desenvolvimento, provavelmente em função do tipo de amostragem utilizada e do alimento consumido pelos indivíduo

Community structure of fish larvae in different biotopes of a neotropical river

Spatial heterogeneity is one of the major sources of compositional dissimilarity among fish in different biotopes. The availability and distribution of refuge, food, and habitats for breeding are determinants of the presence of fish species with different life histories, and understanding how this composition is organized along an environmental gradient is important for the protection of fish spawning sites and preservation of conditions that favor the dispersion and growth of their larvae. Thus, this study aimed to evaluate how the ichthyoplankton community is structured in different biotopes (river, lake, and transitional) of a fluvial system and to determine the factors involved in the structuring process. We conducted sampling in the lower Ivinhema River, upper Paraná River floodplain, Brazil, during two consecutive reproductive periods between 2010 and 2012. Larvae of long-distance migratory species were more related to the river biotope, while the non-migratory or short-distance migrators were more associated with transitional and lake biotopes. Therefore, our results indicate that the hydrodynamic conditions of the river, especially the flow velocity, as well as the parental reproductive guild, influence the distribution patterns of the ichthyoplankton community