Mercury concentrations and differences in isotopic niches of fish from upstream and downstream of an Amazon reservoir dam.

Reservoir construction promotes many environmental impacts, including the enhancement of mercury concentrations in fish. The processes that can influence mercury concentrations in fish in Amazonian reservoirs are still little explored in depth, especially when we consider the possible particularities of the ecosystems in question. This study aims to investigate how mercury concentrations in fish could be influenced by the Tucuruí dam, considering possible changes in their feeding and trophic position according to the dam position (up or downstream). Fish were sampled upstream and downstream of the Tucuruí reservoir, and total mercury (THg) and stable isotopes of carbon and nitrogen (δ15N and δ13C) were measured in muscles. We observed three different Hg bioaccumulation patterns influenced by the dam. These differences occurred due to species trophic niche changes corroborated by the isotope analysis. Higher THg concentrations downstream compared to those upstream ones were only observed for Geophagus proximus. On the contrary, Plagioscion squamosissimus, from downstream, presented lower concentrations than upstream ones. The isotopic niche of these two species presented different changes according to the sampled site. THg biomagnification was higher upstream compared to downstream, considering that the regression slope was approximately two times higher upstream versus downstream. THg concentrations in fish were explained by the differences in their feeding habits according to their location in relation to the dam. The difference in THg biomagnification was able to reflect differences in structure of the food web chain in ecosystems under the dam's influence.

Identification of fish specimens of the Tocantins River, Brazil, using DNA barcoding.

The fish fauna of the Tocantins River possesses many endemic species; however, it is little studied in molecular terms and is quite threatened by the construction of several hydroelectric dams. Therefore, the objective of this study was to identify the ichthyofauna of the Tocantins River using DNA barcoding. For this, collections were carried out in five points of this river, which resulted in the capture of 725 individuals from which partial sequences of the cytochrome oxidase subunit I (COI) gene were obtained for genetic analysis. A total of 443 haplotypes were recovered with the mean intraspecific K2P genetic distance of 1.82%. Altogether, 138 species were identified based on morphological criteria, which was a quantity that was much lower than that indicated by the four molecular methods (assemble species by automatic partitioning [ASAP], barcode index number [BIN], generalized mixed Yule coalescent (GMYC), and Bayesian Poisson tree processes [bPTP]) through which 152-157 molecular entities were identified. In all, 41 unique BINs were obtained based on the data generated in the BOLDSystems platform. According to the result indicated by ASAP (species delimitation approach considered the most appropriate in the present study), there was an increase of 17 molecular entities (12.32%), when compared to the number of species identified through their morphological criteria, as it can show cryptic diversity, candidates for new species, and misidentifications. There were 21 incongruities indicated between the different identification approaches for species. Therefore, it is suggested that these taxonomic problems be cautiously evaluated by experts to solve such taxonomic issues.

Ten years later: An update on the status of collections of endemic Gulf of Mexico fishes put at risk by the 2010 Oil Spill.

The 2010 Gulf of Mexico Deepwater Horizon was the largest oil spill in human history that occurred during a 12-week period in a region less than 100 km from the coast of Louisiana; however, after more than a decade of post-spill research, few definitives can be said to be known about the long-term impacts on the development and distribution of fishes in and around the region of the disaster. Here, we examine endemic Gulf of Mexico fish species that may have been most impacted by noting their past distributions in the region of the spill and examining data of known collecting events and observations over the last twenty years (ten years prior to the spill, ten years post-spill). Five years post-spill, it was reported that 48 of the Gulf's endemic fish species had not been collected and, with expanded methods, we now report that 29 (of the 78 endemic species) have not been reported in collections since 2010 (five of these are only known from observations post-spill). Although the good news that some previously 'missing' species have been found may be cause to celebrate, the lack of information for many species remains a cause for concern given focused sampling efforts post-spill.

Multiple habitats drive the functional diversity of fish assemblages in a tropical estuary.

Understanding estuarine diversity patterns is crucial to highlight the ecological value of coastal ecosystems for fish assemblages. To increase our knowledge, we investigated the functional diversity of fish assemblages in five estuarine habitats (sandy beaches, mudflats, seagrass meadows, mangrove fringes, and estuarine riparian vegetation) in a tropical estuary of Brazil. Functional diversity metrics were assessed considering seven fish functional traits and calculated using functional indices, PCoA (functional spaces), and community-weighted mean (CWM). Then, a unified RLQ and fourth-corner analysis were used to evaluate environment-trait relationships. A total of 27,036 individuals of 119 species were recorded in all habitats. Functional diversity showed similar trends to estuarine habitats, which were more driven by the spatial configuration rather than by their structure, emphasizing the importance of environmental heterogeneity. There was a greater occupation of functional space to habitats located in the lower estuary compared to the upper estuary. Furthermore, body shapes and trophic guilds were the most common traits related to changes in functional diversity between habitats. The RLQ analysis revealed differences in trait composition between habitats influenced by salinity and transparency, although the fourth corner method did not show a significant relationship between fish functional traits and environmental variables. Our results suggest that the mosaic of habitats support the high functional diversity of fishes in tropical estuaries.

Occurrence of tripletail Lobotes surinamensis (Bloch, 1790) in the inner Bristol Channel, UK.

A specimen of tripletail Lobotes surinamensis (total length: 402 mm, total mass: 1262 g) was caught in the shallow waters of the inner Bristol Channel on September 2, 2019, with this only the second known capture of this species from the British Isles. Given the cosmopolitan distribution of this species, the potential origin of this specimen is uncertain.

Fish fauna of the Río San Pedro and Río La Pasión, Usumacinta River Basin, Guatemala / Ictiofauna del Río San Pedro y Río La Pasión, Usumacinta River Basin, Guatemala

Abstract The Río San Pedro and Río La Pasión lie within the Usumacinta River Basin, a globally significant center of freshwater fish diversity. Both rivers are listed among Central America's top 50 regions for conserving freshwater biodiversity. This study presents an updated checklist of 70 fish species, of which six are non-native to the Usumacinta River Basin. From these species, 69 are reported from the Río La Pasión and 56 reported from the Río San Pedro, representing higher species richness than previously reported. The checklist derives from a systematic survey of fishes conducted in 2019 and records available in public databases and published literature. Seventy-eight percent of the species were reported in both rivers, and Cichlidae and Poeciliidae had the most species. Secondary species represent 59% of the species reported, followed by peripheral species with 22% of the species. The species with highest fidelity in Río La Pasión were the armored catfish Pterygopichthys spp. and the livebearer Gambusia sexradiata; and the cichlids Thorichthys meeki and Oscura heterospila had highest fidelity in the Río San Pedro. Thorichthys helleri was widely distributed in both rivers. According to the IUCN Red List of Threatened Species, there are four species classified as Vulnerable in Río La Pasión. However, 62% of the species are of Least Concern, 25% of the species are Data Deficient, and 6% are listed as Not Evaluated. More research is needed to document the status of the fish fauna, and improved habitat protection is required to conserve stocks.

Resumen El río San Pedro y el río La Pasión se encuentran dentro de la cuenca del río Usumacinta, un centro de diversidad de peces de agua dulce de importancia mundial. Ambos ríos figuran entre las 50 regiones principales de América Central para conservar la biodiversidad de agua dulce. Este estudio presenta un listado actualizado de 70 especies de peces, de las cuales 6 son especies no nativas para la cuenca del Río Usumacinta. De estas especies, 69 se reportan para el Río La Pasión y 56 para el río San Pedro, lo que representa una riqueza de especies más alta que la reportada previamente. La lista de verificación se deriva de un muestreo sistemático de peces realizado en 2019 y registros disponibles en bases de datos públicas y literatura publicada. El 78% de las especies se reportan en ambos ríos, siendo Cichlidae y Poeciliidae las familias con mayor riqueza. Las especies con mayor fidelidad en Río La Pasión fueron el bagre acorazado Pterygopichthys spp. y el pez vivíparo Gambusia sexradiata; y los cíclidos Thorichthys meeki y Oscura heterospila tuvieron mayor fidelidad en el Río San Pedro. Thorichthys helleri se distribuyó ampliamente en ambos ríos. Según la Lista Roja de Especies Amenazadas de la UICN, existen cuatro especies clasificadas como Vulnerable en el Río La Pasión. Sin embargo, el 62 % de las especies son de Preocupación Menor, el 25 % de las especies tienen Datos Insuficientes y el 6 % se enumeran como No Evaluadas. Se necesita más investigación para documentar el estado de la fauna de peces, y se requiere una mejor protección del hábitat para conservar las poblaciones.

Fishes from affluents of Rio Branco, Municipality of Caracaraí, Roraima State, northern Brazil / Peixes de afluentes do Rio Branco, Município de Caracaraí, Estado de Roraima, norte do Brasil

Abstract The Amazon has the richest freshwater ichthyofauna of the planet, with tens of new species being described annually. Although studies on Amazonian fish in the literature are increasingly common recently, there are still significant gaps concerning primary data on the ichthyofauna. One such gap is the state of Roraima and its main drainage, Rio Branco. There is a single book published in 2007 on fishes of Rio Branco, and although it presents a rather complete list of over 580 species known until then, the information is now a little outdated and many species found in some of its affluents are not listed in the book. Due to the scarcity of published data on the fish diversity of Roraima and taking into account that ichthyofaunal surveys are important tools towards freshwater conservation, we carried out an inventory of the ichthyofauna in the region of Caracaraí (RR) in 18 sampling sites including seven affluents of both left and right margins of Rio Branco. We recorded a total of 64 species of 41 genera and 18 families of five orders that occur in the Neotropical region, representing more than 11% of the species previously registered in the book for the entire Rio Branco basin. Twelve species were added to the list presented in the book, with four representing first records for the basin, one of them a new record for Brazil. Two of the 64 species are putative new taxa in need of further taxonomic studies. The order with the highest diversity was Characiformes (40 species), with highlights for the family Characidae (24 of these species), followed by Cichliformes (11 species) and Siluriformes (9 species). The richest collecting sites had 23 species, and the least rich site had only two species. Hyphessobrycon bentosi and Nannostomus marginatus occurred in more than 60% of the sites. There has been a significant difference in the exclusive ichthyofauna from affluents of both margins of Rio Branco, with the number of exclusive species in left margin tributaries approximately five times higher. Results presented herein complement data from the literature regarding the still poorly known ichthyofauna from Roraima.

Resumo A Amazônia possui a mais rica ictiofauna de água doce do planeta, com dezenas de novas espécies sendo descrita anualmente. Apesar de estudos sobre os peixes amazônicos serem cada vez mais comuns na literatura, ainda existem lacunas importantes com relação aos dados primários da ictiofauna. Uma dessas lacunas é o estado de Roraima e sua principal bacia hidrográfica, o Rio Branco. Até hoje, há apenas um livro publicado em 2007 sobre os peixes do Rio Branco, e apesar de apresentar uma lista bastante completa com pouco mais de 580 espécies conhecidas até então, atualmente as informações estão um pouco desatualizadas e diversas espécies de peixes encontradas em alguns de seus afluentes não constam do livro. Devido a escassez de dados publicados sobre a diversidade de peixes de Roraima e levando em consideração que levantamentos de ictiofauna são ferramentas importantes para mensurar o potencial de conservação dos corpos d'água, nós fizemos um levantamento da ictiofauna da região de Caracaraí (RR) em 18 pontos incluindo sete afluentes das margens esquerda e direita do Rio Branco. Foram registradas ao todo 64 espécies de 41 gêneros e 18 famílias de peixes de cinco ordens que ocorrem na região Neotropical, representando pouco mais de 11% das espécies registradas no livro para toda a bacia do Rio Branco. Doze espécies foram adicionadas à lista apresentada no livro, sendo quatro registradas pela primeira vez neste estudo, uma delas registrada pela primeira vez no Brasil. Duas das 64 espécies representam possíveis espécies ainda não descritas, necessitando de estudos taxonômicos mais aprofundados. A ordem com maior diversidade foi Characiformes (40 espécies), com destaque para a família Characidae (24 destas espécies), seguida de Cichliformes (11 espécies) e Siluriformes (9 espécies). Os pontos com maior riqueza apresentaram 23 espécies e o com menor riqueza apresentou apenas duas espécies. Hyphessobrycon bentosi e Nannostomus marginatus ocorreram em mais de 60% dos pontos. Houve diferença significativa na ictiofauna exclusiva entre os afluentes das duas margens do Rio Branco, com o número de espécies exclusivas da margem esquerda sendo aproximadamente cinco vezes maior. Os resultados apresentados aqui complementam os dados presentes na literatura a respeito da ainda pouco estudada ictiofauna de Roraima.

Assessment of ichthyofaunal diversity of family Cyprinidae in River Panjkora Dir, Khyber Pakhtunkhwa, Pakistan / Avaliação da diversidade ictiofaunística da família Cyprinidae no rio Panjkora Dir, Khyber Pakhtunkhwa, Paquistão

The study explores the Ichthyofaunal diversity of freshwater Cyprinidae fish in the Panjkora River of Dir, Khyber Pakhtunkhwa, Pakistan. A total of 911 fish samples were collected from 5 different sites along the river and identified using standard identification keys. Out of the 911 fish samples, 204 were related to family Cyprinidae, having 4 sub families, i.e Cyprininae representing 3 species i.e Carassius auratus, Cyprinus carpio, Cyprinus watsoni, Danioninae representing 6 species i.e Barilius modestus, Barilius vagra, Barilius pakistanicus, Amblypharangodon mola, Salmophasia punjabensis, Rasbora daniconius, Labeoninae representing 5 species i.e Tor putitora, Crossocheilus diplocheilus, Gara gotyla, Labeo rohita, Labeo diplocheilus, and Barbinae representing 6 species i.e Puntius ticto, Puntius sophore, Puntius chonchonius, Schizothorax esocinus, Schizothorax labiatus and Schizothorax plagiostomus. This study adds 6 new species i.e Amblypharangodon mola, Salmophasia punjabensis, Labeo rohita, Labeo diplocheilus, Puntius chonchonius and Rasbora daniconius for the 1st time which are not reported earlier. EXCEL 2019 and XLSTAT were used for principal components analysis to study richness and correlation of fish diversity. Eigenvalues obtained from Sheringal to Zulam are 3.72, 0.511, 0.37, 0.29 and 0.09 respectively. The higher eigenvalue of Sheringal site shows higher diversity. Water quality study shows that the mean values of water temperature was 16.8°C, pH 7.08, total hardness134.6 mg/L, alkalinity 89.3 mg/L, Nitrate 5.93 mg/L, Chlorine 0.87 mg/L, Nitrite0.02 mg/L and Copper 0.04 mg/L, Iron 0.07 mg/L, Lead 0.002 mg/L. The physicochemical parameters of river Panjkora during the study time remained within the permissible limits as prescribed by the WHO (2005). Gut analysis revealed the presence of algae, nymphs insect's larvae, macroinvertebrates and protozoans.

O presente estudo explora a diversidade ictiofaunística de peixes Cyprinidae de água doce no rio Panjkora de Dir, Khyber Pakhtoonkhwa, Paquistão. Um total de 911 amostras de peixes foram coletadas em 5 locais diferentes ao longo do rio e identificadas usando chaves de identificação padrão. Das 911 amostras de peixes, 204 eram relacionadas à família Cyprinidae, com 4 subfamílias, ou seja, Cyprininae representando 3 espécies, isto é, Carassius auratus, Cyprinus carpio, Cyprinus watsoni, Danioninae, representando 6 espécies, ou seja, Barilius modestus, Barilius vagra, Barilius pakistanicus, Amblypharangodon mola, Salmophasia punjabensis, Rasbora daniconius, Labeoninae representando 5 espécies, ou seja, Tor putitora, Crossocheilus diplocheilus, Gara gotyla, Labeo rohita, Labeo diplocheilus e Barbinae, representando 6 espécies, ou seja, Puntius ticto, Puntius sophore, Puntius chonchonius, Schizothorax esocinus, Schizothorax labiatus e Schizothorax plagio estoma. Este estudo adiciona 6 novas espécies, como Amblypharangodon mola, Salmophasia punjabensis, Labeo rohita, Labeo diplocheilus, Puntius chonchonius e Rasbora daniconius pela primeira vez, que não foram relatadas anteriormente. EXCEL 2019 e XLSTAT foram usados para análise de componentes principais para estudar a riqueza e correlação da diversidade de peixes. Os autovalores obtidos de Sheringal a Zulam são 3,72, 0,511, 0,37, 0,29 e 0,09, respectivamente. O autovalor mais alto do site Sheringal mostra maior diversidade. O estudo da qualidade da água mostra que os valores médios da temperatura da água foram 16,8 °C, pH 7,08, dureza total 134,6 mg/L, alcalinidade 89,3 mg/L, Nitrato 5,93 mg/L, Cloro 0,87 mg/L, Nitrito 0,02 mg/ L e Cobre 0,04 mg/L, Ferro 0,07 mg/L, Chumbo 0,002 mg/L. Os parâmetros físico-químicos do rio Panjkora durante o tempo de estudo permaneceram nos limites permitidos conforme prescrito pela OMS (2005). A análise intestinal revelou a presença de algas, ninfas, larvas de insetos, macroinvertebrados e protozoários.

Influence of sewage discharge on dissolved oxygen concentration and fish diversity in the Girado stream and Chascomús lake.

Hypoxic aquatic environments have increased in recent decades mainly by human activities that generate pollution. The objective of this work was to study the influence of the discharge of sewage effluents from Chascomús city on the concentration of dissolved oxygen (DO) in the Girado stream and its connection with Chascomús lake and analyze the impact on fish biodiversity. Four sites were selected to measure DO and temperature weekly for one year: discharge of sewage effluent, union of the sewage effluent with the Girado stream, Girado stream and Chascomús lake. Also, ichthyological samplings were carried out in a presumed hypoxic zone and a normoxic zone of the Girado stream. The results showed that there were two hypoxic zones corresponding to the sewage effluent and the union of the effluent with the Girado stream (~3 mg l-1). Also, two normoxic zones were identified, the course of the Girado stream and the union with Chascomús lake (~ 8 mg l-1). In these areas the water temperature varied according to the seasonality of the region (from 10 to 30 °C) without differences between zones. It is important to note that these areas received a constant flow of sewage effluent from Chascomús city (~ 885,600 l per day). In the fish sampling carried out in the 4 seasons of the year, 14 typical species of the Pampas lakes were captured with species more tolerant to low DO. Pejerrey were captured in a small number in both sites but with no signs of abnormalities in the gonads.

Are fish assemblages recovering after the huge disaster of mining tailing dam collapse in Mariana (Brazil-MG)?

The Doce River basin is located in the Brazilian states of Minas Gerais (MG) and Espírito Santo (ES). Anthropogenic expansion throughout the twentieth century heavily modified the bioecological configuration of the region, which was worsened in November 2015 by the collapse of the Fundão tailing dam in Mariana municipality (MG). Local ichthyofauna suffered a loss of environmental quality, which served as an alert to the possible decline of native species and transformation of fish assemblages. Through a systematic literature review, the present study aimed to investigate the recovery stage of fish assemblage after the disaster. To accomplish this, we selected 14 documents reporting species lists and fish distributions in the area principally affected by the disaster. Data collected about fish assemblage (presence/absence) were spatially (upper, middle, and lower sections) and temporally (pre- and post-disaster) arranged, followed by non-metric multidimensional scaling (NMDS) analysis to assess similarity. We applied the Analysis of Similarities (ANOSIM) non-parametric test to confirm statistically significant differences between groups. We complemented the study by searching for the main bioecological characteristics of the most frequent species raised among the selected documents. NMDS showed differences in the similarity of fish assemblages among the three spatial sections, as confirmed by ANOSIM (p < 0.05), but no differences for the temporal component were observed. Nevertheless, we detected a trend based on continental fish assemblage transformation, as determined by the presence of many non-native species in the post-disaster period, suggesting the better resilience of these species over that of native species. The missing of many native species previously easily collected, mainly from the families Characidae, Loricariidae, and Trichomycteridae, suggested the system moving toward a new condition, probably worsened than the previous one. The ichthyofauna of the estuarine environment, on the contrary, seems to have recovered faster than ichthyofauna from the continental environment.

Non-native freshwater fish from drainages of Rio Grande do Sul State, Brazil

The present study catalogues exotic and allochthonous fish species found in the three main freshwater river drain-ages of Rio Grande do Sul State using records of scientific collections and literature, and discusses the main impacts caused by their introduction in natural environments. Ten exotic species are found in the area, i.e., Clarias gariepinus, Coptodon ren-dalli, Ctenopharyngodon idella, Cyprinus carpio, Hypophthalmichthys molitrix, Hypophthalmichthys nobilis, Ictalurus punctatus, Micropterus salmoides, Oncorhynchus mykiss and Oreochromis niloticus, belonging to five orders, nine genera and seven fami-lies. These fishes are native from African, Asian, European and North American countries. The eight allochthonous species, i.e., Acestrorhynchus pantaneiro, Hoplerythrinus unitaeniatus, Hoplias lacerdae, Megaleporinus macrocephalus, Piaractus mesopota-micus, Pachyurus bonariensis, Serrasalmus maculatus, and Trachelyopterus lucenai, belong to three orders, eight genera, and six families, are native from the Río La Plata basin, that includes the Río Uruguay, and have been all registered in the Laguna dos Patos. Two of these species are further recorded in the Rio Tramandaí system (A. pantaneiro and T. lucenai). The study also pre-sentes a brief history of the first records of exotic species in the state and in the country, and their main vectors of introduction. According to the records of exotic species in scientific collections, the two exotic species with the highest number of records in the country are tilapias Coptodon rendalii (508 records) and Oreochromis niloticus (376 records), and most records occurred in the last two decades. The two carps Cyprinus carpio and Ctenopharyngodon idella are the only exotic species recorded in the three main drainage basins of the state. In addition, we warn about the importance of studies about the biology and negative impacts of exotic species over native species on the understanding of management in wild environments.(AU)

Temporal variation in composition, abundance and biomass of the fish fauna after impact on subtropical transitional water

Transitional waters are characterized by large variations in salinity, temperature, turbidity, among other factors, such as tidal cycle, wind action and rainfall, that are constantly changing over time. The distribution of biota in these environments is regulated by these natural variations and also by human activities, such as pollution, overexploitation of resources, acceleration of urbanization, suppression of habitats and changes in hydrological dynamics. The objective of this study was to analyze the temporal dynamics of the fish fauna of the Saco dos Limões Cove, state of Santa Catarina, Brazil, after the construction of a highway. Fish community was evaluated over five years by annual and monthly variation in species richness, abundance and biomass. A total of 17,993 individuals were collected, distributed in 33 families, 59 genera and 79 species. The evaluated years were similar to each other in species composition. Community descriptors varied over time but did not show seasonal trends. In all years, abundance was higher than biomass, indicating both the disturbance and the ecosystem function as a nursery in the studied area. This was corroborated by the large number of juveniles of dominant species (Genidens genidens, Eucinostomus gula and Eucinostomus argenteus).(AU)

Length-weight relationship, sex ratio, and diet of three fish species (Actinopterygii: Teleostei) in streams of the Pomba River basin, Paraíba do Sul river drainage, Southeastern Brazil

This study aimed to estimate the parameters of length-weight relationship, sex ratio, and diet of three freshwater fish species that inhabit streams in the Pomba River basin (Rio de Janeiro, Brazil). Fishes were sampled with seine nets (2.0 × 1.20 m, 2 mm mesh size) and dip nets (0.46 × 0.33 m, 2 mm mesh size) from October to December 2018. Measurements were taken for total length (TL - 0.1 cm precision) and total weight (TW - 0.01 g precision). Growth model parameters were estimated. This study provides new length-weight relationship data for Deuterodon intermedius (Eigenmann, 1908), Australoheros paraibae Ottoni & Costa, 2008, and Hypostomus punctatus Valenciennes, 1840. All of them ingested a wide variety of food items, including plant material like algae, animal material such as terrestrial and aquatic insects, and undefined matter such as detritus or mud. The three species showed a higher number of females. Our study provides basic information for functional diversity studies, as well as for future investigations associated with the evaluation of anthropic impacts, either occasional or chronic, on the fish assemblage structure of the Pomba River basin.(AU)

Length-weight relationships of fish from sandy beaches / Relação peso-comprimento de 16 espécies de peixes que ocorrem perto de praias arenosas ao longo da bacia do baixo rio Negro na Amazônia brasileira

This study estimated the length–weight relationships of 16 fish species occurring close to the shores of sandy beaches along the lower Negro River basin, Brazilian Amazon. The specimens were captured for one day each month, in October to November 2016, early in the morning and early evening, using trawl net (20 m length and 3.5 m height, 5 mm mesh between opposite knots). Measurements were taken for standard length (SL 0.1 cm precision) and total weight (TW 0.01 g precision). The parameters a and b of the equation WT = a.LTb were estimated. The a values ranged from 0.0018 to 0.0226 and b values ranged from 2.5271 to 3.3244. This study also provides new data on of maximum lengths for six species, Amazonsprattus scintilla, Brycon pesu, Moenkhausia megalops, Pachyurus paucirastrus, Reganella depressa and Trachydoras microstomus, and new reports of the LWRs parameters of 15 fish species.(AU)

Este estudo estimou as relações comprimento-peso de 16 espécies de peixes que ocorrem às margens de praias arenosas ao longo da bacia do baixo Rio Negro, Amazônia brasileira. As espécies foram capturadas durante um dia de cada mês, de outubro a novembro de 2016, no início da manhã e no início da noite, usando rede de cerco (20 m de comprimento e 3,5 m de altura, 5 malha mm entre nós opostos). As medidas foram feitas para comprimento padrão (SL - precisão de 0,1 cm) e peso total (TW - precisão de 0,01 g). Os parâmetros a e b da equação WT = a.LTb foram estimados. Os valores de a variaram de 0,0018 a 0,0226 e os valores de b variaram de 2,5271 a 3,3244. Este estudo também fornece novos dados sobre comprimentos máximos para seis espécies, Amazonsprattus scintilla, Brycon pesu, Moenkhausia megalops, Pachyurus paucirastrus, Reganella depressa e Trachydoras microstomus, e novos reportes dos parâmetros da LWRs de 15 espécies de peixes.(AU)

Influence of abiotic factors on the composition of fish assemblages in the Aracá-Demeni sub-basin of the middle Negro River / Influência de fatores abióticos na composição das assembleias de peixes na sub-bacia Aracá-Demeni no médio rio Negro

Abstract We evaluated the influence of flooding and receding comparison and spatial variation on the composition and structure of fish assemblages in blackwater and clearwater rivers of the Aracá-Demeni sub-basin in the middle Negro River, Amazonas state, Brazil. The collections were carried out during the falling-water period (November 2018) and the rising-water period (April 2019) using gillnets with meshes ranging from 30 to 120mm stretched mesh size. Ecological estimates of richness, equitability, the Shannon-Wiener diversity index, and the Berger-Parker index showed no significant differences between the periods. The composition of the ichthyofauna showed variations between the falling-water and rising-water periods. Beta diversity in the Aracá-Demeni sub-basin is almost completely caused by species substitution, with spatial turnover accounting for most of the estimate. The identification of these patterns and of the responsible factors are fundamental for the definition of conservation strategies, especially in an ecosystem whose dynamics can be influenced by climate change through changes in the intensity of the flood pulse and connectivity.

Resumo Avaliamos a influência da variação entre os períodos de enchente e vazante e espacialmente na composição e estrutura das assembleias de peixes em rios de águas pretas e claras da sub-bacia Aracá-Demeni no médio rio Negro, Amazonas, Brasil. As coletas foram realizadas durante o período de vazante (novembro de 2018) e o período de enchente (abril de 2019) utilizando redes de espera com malhas variando de 30 a 120mm entre nós opostos. As estimativas ecológicas de riqueza, equitabilidade, índice de diversidade de Shannon-Wiener e índice de Berger-Parker não apresentaram diferenças significativas entre os períodos. A composição da ictiofauna apresentou variações entre os períodos de vazante e enchente. A diversidade beta na sub-bacia Aracá-Demeni é quase totalmente causada pela substituição de espécies, com a renovação espacial respondendo pela maior parte da estimativa. A identificação desses padrões e os fatores responsáveis são fundamentais para a definição de estratégias de conservação, principalmente em um ecossistema cuja dinâmica pode ser influenciada pelas mudanças climáticas por meio de mudanças na intensidade do pulso de inundação e conectividade.

Length-weight relationships of fish from sandy beaches / Relação peso-comprimento de 16 espécies de peixes que ocorrem perto de praias arenosas ao longo da bacia do baixo rio Negro na Amazônia brasileira

Abstract This study estimated the length-weight relationships of 16 fish species occurring close to the shores of sandy beaches along the lower Negro River basin, Brazilian Amazon. The specimens were captured for one day each month, in October to November 2016, early in the morning and early evening, using trawl net (20 m taken for standard length (SL - 0.1 cm precision) and total weight (TW - 0.01 g precision). The parameters a and b of the equation WT = a.LTb were estimated. The a values ranged from 0.0018 to 0.0226 and b values ranged from 2.5271 to 3.3244. This study also provides new data on of maximum lengths for six species, Amazonsprattus scintilla, Brycon pesu, Moenkhausia megalops, Pachyurus paucirastrus, Reganella depressa and Trachydoras microstomus, and new reports of the LWRs parameters of 15 fish species.

Resumo Este estudo estimou as relações comprimento-peso de 16 espécies de peixes que ocorrem às margens de praias arenosas ao longo da bacia do baixo Rio Negro, Amazônia brasileira. As espécies foram capturadas durante um dia de cada mês, de outubro a novembro de 2016, no início da manhã e no início da noite, usando rede de cerco (20 m de comprimento e 3,5 m de altura, 5 malha mm entre nós opostos). As medidas foram feitas para comprimento padrão (SL - precisão de 0,1 cm) e peso total (TW - precisão de 0,01 g). Os parâmetros a e b da equação WT = a.LTb foram estimados. Os valores de a variaram de 0,0018 a 0,0226 e os valores de b variaram de 2,5271 a 3,3244. Este estudo também fornece novos dados sobre comprimentos máximos para seis espécies, Amazonsprattus scintilla, Brycon pesu, Moenkhausia megalops, Pachyurus paucirastrus, Reganella depressa e Trachydoras microstomus, e novos reportes dos parâmetros da LWRs de 15 espécies de peixes.

Fishes from Yarinacocha lake: an emblematic Amazonian ecosystem in the lower Ucayali River basin, Pucallpa, Peru / Peixes do lago Yarinacocha: um ecossistema amazônico emblemático na bacia do baixo rio Ucayali, Pucallpa, Peru

The Yarinacocha lake is an emblematic ecosystem of the Peruvian Amazon, representing the main point of fish landing and a tourist attraction in the city of Pucallpa. The wide fauna diversity in this area has made it the target of various studies, although for fish species most of them were focused on commercial species. In this work, we carried out the first ichthyofauna species inventory of the Yarinacocha lake, sampling throughout the entire lake during the rainy and dry seasons and considering also all previously recorded species deposited in the Ichthyological Collection of the MUSM with the same locality. A total of 164 fish species were recorded, representing 10 orders (plus Eupercaria), 34 families and 116 genera. Characiformes was the order with more species (68 spp., 41.5%) followed by Siluriformes (59 spp., 36%), Cichliformes (17 spp., 10.5%), and Gymnotiformes (8 spp., 4.9%). The most highly represented families, including almost 55.5% of the total diversity obtained, were Characidae (23 spp., 14%), followed by Cichlidae (17 spp., 10.4%), Loricariidae (14 spp., 8.5%), Pimelodidae (13 spp., 7.9%), Doradidae (13 spp., 7.4%) and Anostomidae (12 spp., 7.3%). From the total fish species recorded in this study, only 22 are considered protected species following the IUCN criteria and 109 species have commercial importance, including 90 ornamental species (54.8%). Our results contribute to the knowledge of the ichthyofauna of the Yarinacocha lake and can be used as a starting point for its conservation and sustainable management over time.

O lago Yarinacocha é um ecossistema emblemático da Amazônia peruana, representando o principal ponto de desembarque de peixes e também uma atração turística da cidade de Pucallpa. A grande diversidade faunística nesta área a tornou alvo de vários estudos, embora para as espécies de peixes a maioria deles tenha sido focada em espécies comerciais. Neste trabalho, realizamos o primeiro inventário da ictiofauna do lago Yarinacocha, amostrando todo o lago durante as estações chuvosa e seca, e também considerando todas as espécies depositadas na Coleção Ictiológica do MUSM dessa localidade. Um total de 164 espécies de peixes foram registradas, representando 10 ordens (mais Eupercaria), 34 famílias e 116 gêneros. Characiformes foi a ordem com mais espécies (68 espécies, 41,5%), seguida por Siluriformes (59 espécies, 36%), Cichliformes (17 espécies, 10,5%) e Gymnotiformes (8 espécies, 4,9%). As famílias mais representadas, incluindo quase 55,5% da diversidade total obtida, foram Characidae (23 spp., 14%), seguido por Cichlidae (17 spp., 10,4%), Loricariidae (14 spp., 8,5%), Pimelodidae (13 spp., 7,9%), Doradidae (13 spp., 7,4%) e Anostomidae (12 spp., 7,3%). Do total de espécies de peixes registradas neste estudo, apenas 22 são consideradas espécies protegidas seguindo os critérios da IUCN e 109 espécies têm importância comercial, incluindo 90 espécies ornamentais (54,8%). Nossos resultados contribuem para o conhecimento da ictiofauna do lago Yarinacocha e podem ser utilizados como ponto de partida para sua conservação e manejo sustentável ao longo do tempo.

Length-weight relationships of fish from sandy beaches / Relação peso-comprimento de 16 espécies de peixes que ocorrem perto de praias arenosas ao longo da bacia do baixo rio Negro na Amazônia brasileira

This study estimated the length–weight relationships of 16 fish species occurring close to the shores of sandy beaches along the lower Negro River basin, Brazilian Amazon. The specimens were captured for one day each month, in October to November 2016, early in the morning and early evening, using trawl net (20 m length and 3.5 m height, 5 mm mesh between opposite knots). Measurements were taken for standard length (SL – 0.1 cm precision) and total weight (TW – 0.01 g precision). The parameters a and b of the equation WT = a.LTb were estimated. The a values ranged from 0.0018 to 0.0226 and b values ranged from 2.5271 to 3.3244. This study also provides new data on of maximum lengths for six species, Amazonsprattus scintilla, Brycon pesu, Moenkhausia megalops, Pachyurus paucirastrus, Reganella depressa and Trachydoras microstomus, and new reports of the LWRs parameters of 15 fish species.

Este estudo estimou as relações comprimento-peso de 16 espécies de peixes que ocorrem às margens de praias arenosas ao longo da bacia do baixo Rio Negro, Amazônia brasileira. As espécies foram capturadas durante um dia de cada mês, de outubro a novembro de 2016, no início da manhã e no início da noite, usando rede de cerco (20 m de comprimento e 3,5 m de altura, 5 malha mm entre nós opostos). As medidas foram feitas para comprimento padrão (SL - precisão de 0,1 cm) e peso total (TW - precisão de 0,01 g). Os parâmetros a e b da equação WT = a.LTb foram estimados. Os valores de a variaram de 0,0018 a 0,0226 e os valores de b variaram de 2,5271 a 3,3244. Este estudo também fornece novos dados sobre comprimentos máximos para seis espécies, Amazonsprattus scintilla, Brycon pesu, Moenkhausia megalops, Pachyurus paucirastrus, Reganella depressa e Trachydoras microstomus, e novos reportes dos parâmetros da LWRs de 15 espécies de peixes.

Length-weight relationships of fish from sandy beaches

Abstract This study estimated the lengthweight relationships of 16 fish species occurring close to the shores of sandy beaches along the lower Negro River basin, Brazilian Amazon. The specimens were captured for one day each month, in October to November 2016, early in the morning and early evening, using trawl net (20 m taken for standard length (SL 0.1 cm precision) and total weight (TW 0.01 g precision). The parameters a and b of the equation WT = a.LTb were estimated. The a values ranged from 0.0018 to 0.0226 and b values ranged from 2.5271 to 3.3244. This study also provides new data on of maximum lengths for six species, Amazonsprattus scintilla, Brycon pesu, Moenkhausia megalops, Pachyurus paucirastrus, Reganella depressa and Trachydoras microstomus, and new reports of the LWRs parameters of 15 fish species.

Resumo Este estudo estimou as relações comprimento-peso de 16 espécies de peixes que ocorrem às margens de praias arenosas ao longo da bacia do baixo Rio Negro, Amazônia brasileira. As espécies foram capturadas durante um dia de cada mês, de outubro a novembro de 2016, no início da manhã e no início da noite, usando rede de cerco (20 m de comprimento e 3,5 m de altura, 5 malha mm entre nós opostos). As medidas foram feitas para comprimento padrão (SL - precisão de 0,1 cm) e peso total (TW - precisão de 0,01 g). Os parâmetros a e b da equação WT = a.LTb foram estimados. Os valores de a variaram de 0,0018 a 0,0226 e os valores de b variaram de 2,5271 a 3,3244. Este estudo também fornece novos dados sobre comprimentos máximos para seis espécies, Amazonsprattus scintilla, Brycon pesu, Moenkhausia megalops, Pachyurus paucirastrus, Reganella depressa e Trachydoras microstomus, e novos reportes dos parâmetros da LWRs de 15 espécies de peixes.

Fish responses to multiple scales in coastal blackwater Atlantic Forest streams in Southeast Brazil

Environmental factors act at multiple spatial scales in a hierarchical manner to shape the organization of biota. However, the relative influence of different scale-related factors is poorly known, especially in Atlantic Forest Blackwater streams. Therefore, we herein aimed to evaluate local, landscape and spatial factors that shape fish assemblages in 14 blackwater restinga coastal Atlantic Forest streams under natural conditions and verify species occurrence patterns among four sub-basins during the low-precipitation season. When we combined local, landscape and spatial factors, variance partitioning explained a high proportion of variation in species matrix. Local variables pH and Total Dissolved Solids explained most of the variability, and these were the most important factors in determining fish community structure. Significant differences in fish assemblage structure among the four sub-basins were observed, and Mimagoniates microlepis, Phalloceros harpagos, and Hollandichthys multifasciatus were the species that most contributed to this dissimilarity. The important contribution of local predictors, the high number of endemic species herein recorded, the presence of an endangered species (Spintherobolus broccae), and near pristine conditions, may be used as baseline conditions for the assessment of similar environments.

Fatores ambientais atuam em múltiplas escalas espaciais de forma hierárquica, moldando a organização da biota. Todavia, as influências relativas de fatores relacionados a diferentes escalas são ainda pouco conhecidas, especialmente em riachos de águas pretas da Mata Atlântica. Investigamos como os fatores locais, da paisagem e espaciais, moldam as assembleias de peixes em 14 riachos costeiros de restinga de águas pretas da Mata Atlântica sob condições naturais, verificando os padrões de ocorrência de espécies em quatro sub-bacias durante a estação de baixa precipitação. A partição de variância explicou uma alta proporção de variação na matriz de espécies ao combinar fatores locais, de paisagem e espaciais. As variáveis ​ locais pH e Sólidos Totais Dissolvidos explicaram a maior parte da variabilidade e foram os fatores mais importantes na estruturação da comunidade de peixes. Foram observadas diferenças significativas na estrutura da assembleia de peixes entre as quatro sub-bacias, sendo que Mimagoniates microlepis, Phalloceros harpagos e Hollandichthys multifasciatus foram as espécies que mais contribuíram para essa dissimilaridade. A importante contribuição dos preditores locais, o alto número de espécies endêmicas e a presença de uma espécie ameaçada (Spintherobolus broccae) indicam condições próximas das pristinas dos riachos, podendo estes ser usados como referência para a avaliação de ambientes semelhantes.