No abstract

The present study provides the length–weight relationships (LWR) for eight fish species in 19 streams from the Pedreira River basin, a small tributary of the Guyana coastal drainages from Amapá State, Brazil. Fishes were collected at two occasions, one in November 2016, the other in July 2018, using hand nets, with 0.5 mm of mesh size and 0.25 m2 of mouth area, and trawl nets, with 0.5 mm of mesh size and 3 m long. Standard length and total weight were measured to determine the LWRs. The results show that the coefficient b varied between 2.798 and 3.380 and thus the values were within the expected range.

RESUMO. O objetivo deste trabalho foi analisar a densidade e estrutura populacional do caranguejo-uçá, com vistas ao seu potencial extrativo em manguezais da Reserva Extrativista Marinha de Tracuateua-PA. As coletas foram realizadas entre os meses de fevereiro a agosto de 2015. A densidade populacional foi calculada em G/m². A Captura por Unidade de Esforço (CPUE) foi obtida através da razão (caranguejos/homem/hora), com o auxílio de um catador experiente de caranguejos. Os animais capturados tiveram as medidas da (LC) e (CC) mensuradas com paquímetro (0,01 mm). O peso (P) foi registrado em balança de precisão (0,01 g). Os potenciais extrativos imediato (PEI) e futuro (PEF) foram avaliados com base na (LC mm), sendo PEI: LC≥60mm e PEF: LC<60mm, considerando o tamanho da maturidade sexual. A análise estatística foi realizada no programa Bioestat 5.0. Os resultados revelaram que a média geral de LC (mm), CC (mm) e P (g) foram de (71,39 ± 5,75; 52,85 ± 4,09; 159 ± 34), respectivamente. O PEI e PEF foram de 95,11 e 4,89%, respectivamente. A maior CPUE foi no manguezal Beiradão (100 indivíduos). A densidade foi maior no manguezal Alemanha com 2,1 G/m², não ocorrendo diferença de médias entre as áreas (p >0,05). Os manguezais da RESEX não evidenciaram desequilíbrio da população de Ucides cordatus. Porém, ressalta-se a necessidade de estudos mais detalhados, além de medidas integradas mais eficazes, que contribuam com a melhoria de vida das comunidades humanas do entorno da RESEX para que a população de U. cordatus não entre em declínio.

The Neotropical region hosts 4225 freshwater fish species, ranking first among the world's most diverse regions for freshwater fishes. Our NEOTROPICAL FRESHWATER FISHES data set is the first to produce a large‐scale Neotropical freshwater fish inventory, covering the entire Neotropical region from Mexico and the Caribbean in the north to the southern limits in Argentina, Paraguay, Chile, and Uruguay. We compiled 185,787 distribution records, with unique georeferenced coordinates, for the 4225 species, represented by occurrence and abundance data. The number of species for the most numerous orders are as follows: Characiformes (1289), Siluriformes (1384), Cichliformes (354), Cyprinodontiformes (245), and Gymnotiformes (135). The most recorded species was the characid Astyanax fasciatus (4696 records). We registered 116,802 distribution records for native species, compared to 1802 distribution records for nonnative species. The main aim of the NEOTROPICAL FRESHWATER FISHES data set was to make these occurrence and abundance data accessible for international researchers to develop ecological and macroecological studies, from local to regional scales, with focal fish species, families, or orders. We anticipate that the NEOTROPICAL FRESHWATER FISHES data set will be valuable for studies on a wide range of ecological processes, such as trophic cascades, fishery pressure, the effects of habitat loss and fragmentation, and the impacts of species invasion and climate change. There are no copyright restrictions on the data, and please cite this data paper when using the data in publications.

Abiotic and biotic factors play an essential role in the structuring of natural communities. Aquatic ecosystems have complex interaction networks, encompassing predator/prey relationships and structural support. Among aquatic organisms, the order Odonata is a model group for understanding those relationships since they can be both predators and prey. Our hypotheses were that Zygoptera are (i) influenced positively by Ephemeroptera, Plecoptera and Trichoptera (EPT) and the Habitat Integrity Index (HII), and negatively by fish and macrophytes; and (ii) Anisoptera are affected positively by EPT and macrophytes, and negatively by fish and HII. We found that Zygoptera were affected by the fish functional trophic groups, while Anisoptera were affected by macrophytes, EPT, fish and HII. Macrophytes affected anisopterans positively because they provide perching sites for adults. The results for EPT and HII may be related since these organisms are also sensitive to environmental changes. More open areas have lower HII values and the negative relationship with Anisoptera may be explained by physiological constraints. The negative relationship between EPT and Anisoptera could be explained by the low occurrence of EPT in open sites, which are the sites that were highly rich in Anisoptera. Finally, the dominance of specific functional trophic groups of fish influences Odonata suborders in different ways. In conclusion, the results show the importance of ecological interactions for Odonata in Amazonian streams in both direct and indirect ways.

The expansion of agriculture in the southeast Amazon-Savanah transitional area has greatly decreased forest cover and influenced stream structure and functioning. We assessed the effects of forest cover loss on the integrity of streams by assessing stream physical conditions and the taxonomic and functional diversity of fish assemblages in this transitional area. We hypothesize that low forest cover, especially adjacent to streams, results in poor physical conditions (e.g., warmer temperatures, less physical structure, etc.), which in turn will decrease the taxonomic and functional diversity of fish assemblages. We detected that loss of forest cover negatively affects natural stream conditions and reduces the functional diversity of fish assemblages, but we did not find a strong effect on taxonomic diversity. Ambush and stalking predators, diurnal surface pickers (groups that exhibit opportunistic life history strategies), grazers, pickers, and browsers (groups that exhibit equilibrium life history strategies) were the functional groups with the strongest relation to altered environments. These groups can explore different niches, both with natural characteristics or altered by human activities. Our results suggest that the preservation of riparian zones can minimize the loss of specialized fish species in assemblages of Amazon-Savannah stream systems.

A major challenge in using recovery techniques, for the different natural ecosystems affected by mining, is a mutual relationship between the habitat and its biota response. This study aimed to do a review to identify the number of publications, which countries are publishing more and which recovery techniques and taxonomic group are used in mining areas globally have contributed to the maintenance or recovery of the environment. We reviewed the literature on recovery in mining areas worldwide, between 1994 and 2016, using the Web of Science online database. We identified 9,000 publications, after the selection procedures, we analyzed the 467 remaining manuscripts. Of these, 34.26% were published between 1994 and 2004, and 65.74% between 2006 and 2016. The countries that contributed the most were the USA with 16.45%, Australia with 13.56% and China with 8.66%. Brazil contributed 6.9% of the publications. The recovery techniques using vegetation were the most reported in the literature and most used. The taxonomic group of terrestrial plants was the most cited and most used in the recovery of degraded areas. We found various techniques for recovering degraded areas can be established, but most of them did not show proper monitoring and without this the recovery processes may not achieve their objectives and studies that test the effect size of these recovery methods are still necessary.

In this study, we assessed the effects of multiple land uses and local habitat variables on the composition of fish functional trophic groups (FTG’s) and on the ecomorphological traits of fish in Amazonian streams. We evaluated land use types and local habitat variables in 26 streams distributed within a land use gradient. Land use and habitat variables affected the composition of FTG’s, as evidenced by the increased abundance of diurnal channel drift feeders in areas with high dissolved oxygen and deeper thalweg. At the same time, diurnal surface pickers, as well as diggers, and ambush and stalker predators were more abundant in streams with higher canopy density. Only habitat variables affected the ecomorphological characteristics of the species. Fish with higher values of relative caudal peduncle length were positively associated with high canopy density, while fish with greater relative mouth width were negatively associated with the variables impact in the riparian zone and cover of fish shelter. The stream fish functional structure was mainly affected by the impacts caused to the local habitat resulting from different land uses. Thus, preserving forest remnants, as well as recovering degraded areas, is essential for the maintenance of aquatic biodiversity in the region.