No abstract

The Itaipu Hydroelectric Power Plant is the second largest in the world in power generation. The artificial barrier created by its dam imposes an obstacle for fish migration. Thus, in 2002, a fish pass system, named Piracema Channel, was built to allow fish to access areas upstream of the reservoir. We tested the potential of environmental DNA metabarcoding to monitor the impact of both the dam and associated fish pass system in the Paraná River fish communities and to compare it with traditional monitoring methods. Using a fragment of the 12S gene, we characterized richness and community composition based on amplicon sequence variants, operational taxonomic units, and zero-radius OTUs. We combined GenBank and in-house data for taxonomic assignment. We found that different bioinformatics approaches showed similar results. Also, we found a decrease in fish diversity from 2019 to 2020 probably due to the recent extreme drought experienced in southeastern Brazil. The highest alpha diversity was recorded in the mouth of the fish pass system, located in a protected valley with the highest environmental heterogeneity. Despite the clear indication that the reference databases need to be continuously improved, our results demonstrate the analytical efficiency of the metabarcoding to monitor fish species.

No abstract

Limnoperna fortunei (Dunker, 1857) is an invasive freshwater bivalve native to rivers and streams of China and Southeast Asia. In 200 1, it was discovered in Itaipu Reservoir, and its population has grown considerably since then. The aim of this study was to estimate density, recruitment, and individual growth of L. fortunei in a subtropical region from a field experiment using an artificial substrate. Samples were collected between December 2004 and December 2005 at Bela Vista Reservoir in Foz do Iguagu, Brazil. Mussels were counted and measured to generate size-frequency and distribution data. Maximum and minimum densities (* standard deviation) were 204 i 17 ind. 100 cm-2 and 94 * 22 ind.lOO ~m -~, respectively. Shell length ranged between 1 and 36 mrn, and shell length frequency indicated presence of young mussels with variable densities throughout the period surveyed. The von Bertalanffy model fitted successfuHy in all cases explaining more than 96% of the variation in shell length. Measured growth parameters (k = 2.35 L, = 38 rnm) were different from those estimated for populations of L. fortunei in a temperate region.

Metabarcoding of environmental DNA is based on primers that are specific to the target taxa (e.g. bacteria, zooplankton, fishes). However, due to the nature of the commonly used protocols, regardless of the chosen primers, several sequences of non-target species will inevitably be generated, but are usually discarded in commonly used bioinformatics pipelines. These non-target sequences might contain important biological information about the presence of other species in the studied habitats and its potential for ecological studies is still poorly understood. Here, we analyzed the presence of mammal and bird species in aquatic environmental samples that were originally amplified targeting teleost fish species. After all cleaning and checking steps, we kept 21 amplicon sequence variants (ASVs) belonging to mammals and ten to birds. Most ASVs were taxonomic assigned to farm/domestic animals, such as cats, cows, and ducks. Yet, we were able to identify a native semi-aquatic mammal, the capybara, in the samples. Four native bird species and a non-native potentially invasive bird (Corvus sp.) were also detected. Although the data derived from these samples for mammals and birds are of limited use for diversity analyses, our results demonstrate the potential of aquatic samples to characterize non-aquatic birds and highlight the presence of a potentially invasive species that had not been recorded before in the region.