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Ichthyofauna of sandy beaches along the Acre river, Brazil
Abstract and Figures
Despite increasing efforts in recent years to catalog the fish diversity of Amazonian rivers, many regions are still under-sampled, and sandy beach environments are particularly poorly understood. The present study focused on a 300 km stretch of the Acre river, in the southwestern Amazon basin, where we sampled 30 sandy beaches separated by a mean interval of 10 km. We collected 15,329 fish representing 80 species, 26 families, and nine orders. The Characiformes were the most abundant order, providing 88.24% of the individuals collected, followed by the Siluriformes, with 10.03%, while the Siluriformes had the highest species richness, with 37 species (45.0%), followed by the Characiformes, with 30 (37.5%). The most abundant species were the characiforms Knodus orteguasae and Creagruto barrigai. Reliable data on a region's biota is fundamental for the evaluation of patterns of biodiversity, and the occurrence and management of threatened species. As fish are directly affected by pollutants and the degradation of aquatic environments, further research in areas that are still poorly sampled will be essential for the elaboration of effective conservation strategies.
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... The spatial arrangement of beaches along a river course creates a fragmented environment, conducive to the colonization and persistence of certain fish species (Winemiller et al. 2010;De Paula and Silva 2019). River beaches are home to a diverse ichthyofauna, predominantly composed of small-sized species, mainly characids and catfishes with a fusiform shape, often forming relatively large schools (Stewart et al. 2002;Duarte et al. 2010;Silva et al. 2020). Smallsized species and juveniles of large-sized species can inhabit beaches seeking protection from predators, taking advantage of characteristics such as high transparency, shallow depth, and low current (Goulding 1997;Lowe-McConnell 1999;Stewart et al. 2002). ...
... This movement to more distant beaches can be hampered by natural physical barriers, such as waterfalls and rapids, which are frequent in the region downstream of the Volta Grande stretch of the Xingu River, resulting in a limitation of the dispersal of these species throughout the aquatic system (Torrente-Vilara et al. 2011;Sawakuchi et al. 2015;Silva et al. 2016). Limitation to dispersal may also occur due to biological barriers, as large rivers are inhabited by larger fish, which may pose a greater risk of predation to small species typical of beach ichthyofauna (Stegmann et al. 2019;Michel et al. 2020;Silva et al. 2020). Thus, the limitation to dispersal may have led beaches located at the extremes of the longitudinal gradient to present similar scores in AEM 2 and 3. ...
In this study, we aimed to identify the factors that drive the patterns in beta diversity of fish assemblages on the beaches of the Volta Grande do Xingu, a river stretch under the influence of Belo Monte dam. Fishes were collected using a trawl net in 28 sandy beaches during the low water period of 2021 (each beach was sampled once during this period). Measurements of environmental variables were carried out on-site, while spatial variables were obtained using Asymmetric Eigenvector Maps (AEM). Using the Bray–Curtis dissimilarity index, we calculated beta diversity and conducted a distance-based redundancy analysis (db-RDA) with the dissimilarity matrix to assess its relationship between beta diversity and environmental and spatial variables. Additionally, we performed a variance partition to quantify the pure and shared contributions of the explanatory matrices to our response matrix. The results revealed low beta diversity among the sampled beaches, and that this beta diversity was explained in part by the spatial variables and pH. Our findings underscore the influence of spatial structure on the assembly of local communities, indicating that dispersion processes and spatial connectivity are relevant mechanisms that contribute to the beta diversity of beach fish communities under influence of a reduced flow by a Hydropower Plant.
... Their waters are home to a very diverse and poorly studied aquatic biota, with fish being the most varied and abundant vertebrate group in this environment (Sleen & Albert, 2017;Duponchelle et al., 2021). Duarte et al. (2019) and Silva et al. (2020) studied the ichthyofauna of beaches and showed critical environments for small fish. Their shallow waters can constitute a refuge environment against catfish and other large fish predators. ...
... These changes along the course of waterways directly affect the aquatic community, changing the environment's quality and the availability of resources and influencing the distribution and composition of macroinvertebrates and fish species (Doretto et al., 2020). There are some studies on the trophic structure of fish assemblages in different environments such as lakes, rapids, streams, macrophyte banks, beaches, and reservoirs (Claro-Jr, 2003;Silva et al., 2020;Jacobs et al., 2021;Melack & Coe, 2021;Nonato et al., 2021;Paula et al., 2021;Silva et al., 2021;Souza et al., 2021), showing a great diversity of diets and food resources. Vannote et al. (1980) proposed the Rio Continuum Theory (TRC), stating a longitudinal gradient of rivers' physicochemical and geomorphological characteristics in the upstreamdownstream direction. ...
Purpose: This study analyzes fish communities' diet and trophic structure on beaches along the Amazon River. Methods: 41 beaches were studied, and fish were collected with 12x3m trawl nets and 5mm mesh between nodes. The stomachs were analyzed using the frequency of occurrence and points method. The dietary index was calculated using the preponderance index (PI). Using IP values, the following trophic categories were established: detritivore, hematophagous, herbivorous, benthic invertivore, pelagic invertivore, terrestrial invertivore, scavenger, and piscivore. Species richness and abundance of fish in trophic categories were related to the longitudinal variation of the sampled sites through linear regression 1,166 stomachs from 119 species were analyzed. Results and discussion: The abundance and richness of detritivore species and the richness of scavengers showed a negative relationship throughout the floodplain, while the number of aquatic invertivore species showed a positive relationship. Implications of the research: The existing differences in beach water quality create a longitudinal conductivity gradient, transparency, and suspended material, gradually altering the environment and composition of the ichthyofauna and the trophic structure along the Amazon River. Originality/value: Ecological studies relating the trophic structure of fish to a large-scale longitudinal gradient are scarce in the Amazon River floodplain, which makes this article an essential piece for better understanding Amazonian systems by characterizing the trophic structure of fish from beaches in a longitudinal gradient of the Amazon River in Brazilian territory.
... Studies conducted in the upper Purus River basin have documented a notably rich ichthyofauna, with 86 species recorded in the Caeté and Macapá rivers (Anjos et al. 2008), 80 species in the Acre River (Silva et al. 2020), and 143 species across various aquatic environments in the Peruvian portion of the Purus River (Albert 2012). However, few studies in the upper Purus River basin have included other bodies of water, such as igarapés, making it difficult to fully understand the true diversity present in the countless water bodies of this region. ...
Few studies have investigated the ichthyofauna of streams in the upper Purus River basin, hampering efforts to understand the diversity of these numerous bodies of water. This study presents the first inventory of the ichthyofauna in the upper Purus-Antimary interfluve, southwestern Amazonia. The study was based on data compiled from various sources, including online repositories, scientific articles, and fish collected from four streams in a protected area. We assessed species richness, distribution area, conservation status and anthropogenic threats. The fieldwork study was carried out in four "terra firme" streams in the Purus River basin, with fieldwork conducted during the rainy season in March and November 2017. We identified a total of 92 species, 26 families, and six orders. The order Characiformes exhibited the highest species richness with 42 species, followed by Siluriformes with 34, and Gymnotiformes with 8 species. The Characidae family was the most diverse, with 25 species, followed by Loricariidae with 11 species and Callichthyidae with seven species. The collected fish samples totaled 1,794 individuals representing 58 species, 22 families, and 4 orders. The most abundant species were Knodus smithi with 307 individuals, followed by Chrysobrycon hesperus with 247 and Tyttocharax madeirae with 165. Most species were classified as being of low conservation concern. The study expanded the known extent of occurrence for Anablepsoides hoetmeri to 2,163.777 km2. Our findings underscore the importance of conserving aquatic habitats and riparian vegetation within the upper Purus-Antimary interfluve, given the presence of a rich and restricted ichthyofauna. Furthermore, we highlight the significant risks posed by anthropogenic pressures such as deforestation for pastures, wildfires, and illegal fishing activities.
... These studies have consistently shown that streams are crucial in sustaining aquatic communities Benone et al., 2020). However, in some areas of the Amazon, such as the western basin, limited research has specifically addressed this question, as most studies in the Brazilian state of Acre have primarily involved species inventories (see Claro-García et al., 2013;Virgílio et al., 2019;Silva et al., 2020). Ramalho et al. (2014) also examined variations in water quality and fish species diversity and composition in the open Campinarana ecosystems of northwestern Acre. ...
We investigated the influence of daily cycle cycleand local environmental factors on fish assemblages in a terra firme stream in southwestern Amazonia during the rainy season. We collected fish by using sieves and hand-nets over three days and local environmental variables were measured throughout the collection period as well. We employed Generalized Linear Models to examine the impact of daily cycle and local environmental variables on fish species richness and abundance. We used PERMANOVA to assess changes in fish assemblage composition and Redundancy Analysis to understand variations in fish species composition in response to daily cycle and local environmental factors. We collected 18 species and 271 individuals, 111 at night and 160 during the day. Dissolved oxygen (DO) had a positive influence on species richness and abundance and species composition differed between daily cycles. Redundancy Analysis revealed associations between fish species composition, environmental variables (temperature, pH and DO), and daily cycle. These findings underscore the significance of the local environment and daily cycle in predicting variations in fish assemblage structure in Amazonian streams. Understanding how stream fish assemblages are organized temporally is important for devising effective conservation strategies in a region facing increasing human pressures on aquatic ecosystems.
... O número de espécies registradas para a área ainda é incipiente, considerando que os corpos d'água da área de abrangência da APA ainda não foram suficientemente estudados. De todo modo, a riqueza da ictiofauna é bem expressiva, considerando-se que em praias ao longo de um trecho de 300 km do rio Acre foi constatada a presença de 80 espécies de peixes(SILVA et al., 2020).Os peixes da APA Lago do Amapá têm sido historicamente utilizados como uma importante fonte de proteína animal para a população local. Um dos motivos é o fácil acesso ao lago e a grande variedade de peixes, permitindo que moradores e visitantes obtenham alimentos frescos e de alto valor nutricional (SEMA, 2010). ...
We conducted a literature review of fish occurring in the Lake Amapá Environmental Protection Area
(EPA) to assess possible threats and identify species with commercial use. A total of six studies on fish
were conducted, totaling 87 recorded species. Although no species were endemic to the Acre River
basin, three were reported to occur strictly in a few Amazonian watersheds. Forty-five species showed
ornamental potential, 31 were used for commercial and subsistence fishing, and 4 were of medical
importance. We highlight that at least five species are priority for conservation and preservation, given
their vulnerability to fishing pressure. Further studies are needed to monitor the degree of species
conservation
... New species are described each year, and the estimates exceed 9,000 species (Reis et al., 2016;Birindelli and Sidlauskas, 2018), for the Neotropical region. For the many water resources that form the Amazon basin, the Acre river is a mediumsized watercourse, by the standards of the Amazon basin, running 1190 km from its source, in Peru, to its confluence with the Purus river in the Brazilian state of Amazonas, first passing through Bolivia and then the state of Acre, Brazil (Silva et al., 2020). For the many water resources that form the Acre river basin, the hydrographic basin Quinoá stream (HBQS), a tributary of the right bank, is an important ecosystem that must be conserved for ecological maintenance and balance (Acre, 2012;Corrêa et al., 2018). ...
A recent expedition to northern Uruguay revealed the presence of the triportheid fish Engraulisoma taeniatum Castro, 1981, which represents the first record of this species in the Uruguay River Basin and for the country. We indicate it as an endangered species for Uruguay considering its restricted distribution in the country and its taxonomic singularity.
A revision of the genus Salminus, excluding the large-sized species S. brasiliensis and S. franciscanus, is presented. In addition to the two large-sized species, four additional Salminus species are recognized: Salminus affinis Steindachner, from the río Magdalena, río Sinú, and río Rancheria basins, Colombia; Salminus hilarii Valenciennes, from the rio Paraná, rio São Francisco, and rio Jaguaribe basins, Brazil, Argentina, and Paraguay; Salminus iquitensis (Nakashima), new combination, from the western portion of the Amazon basin, rio Branco, and río Orinoco basins, Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela; and Salminus santosi new species, from the rio Tocantins basin, Brazil. These four species are described/redescribed and illustrated, and a key to the species belonging to the genus is presented. Comments on the diagnosis of the genus Salminus and its biogeography taking into account recent phylogenetic hypotheses published for the genus, are presented.
The Amazon Basin is an unquestionable biodiversity hotspot, containing the highest freshwater biodiversity on earth and facing off a recent increase in anthropogenic threats. The current knowledge on the spatial distribution of the freshwater fish species is greatly deficient in this basin, preventing a comprehensive understanding of this hyper-diverse ecosystem as a whole. Filling this gap was the priority of a transnational collaborative project, i.e. the AmazonFish project - https://www.amazon-fish.com/. Relying on the outputs of this project, we provide the most complete fish species distribution records covering the whole Amazon drainage. The database, including 2,406 validated freshwater native fish species, 232,936 georeferenced records, results from an extensive survey of species distribution including 590 different sources (e.g. published articles, grey literature, online biodiversity databases and scientific collections from museums and universities worldwide) and field expeditions conducted during the project. This database, delivered at both georeferenced localities (21,500 localities) and sub-drainages grains (144 units), represents a highly valuable source of information for further studies on freshwater fish biodiversity, biogeography and conservation.
This study presents an extensive review of published and unpublished occurrence records of fish species in the Rio Negro drainage system within the Brazilian territory. The data was gathered from two main sources: 1) litterature compilations of species occurrence records, including original descriptions and revisionary studies; and 2) specimens verification at the INPA fish collection. The results reveal a rich and diversified ichthyofauna, with 1,165 species distributed in 17 orders (+ two incertae sedis), 56 families, and 389 genera. A large portion of the fish fauna (54.3% of the species) is composed of small-sized fishes < 10 cm in standard length. The main groups are Characiformes (454 species; 39.0%), Siluriformes (416; 35.7%), Gymnotiformes (105; 9.0%), and Cichliformes (102; 8.8%). The species composition differs between the main aquatic environments, such as: main channel (159 species), lakes (296), tributary rivers (596), small streams (234), seasonal beaches (186), and rapids (41). Part of the ichthyofauna is shared with adjacent basins, such as the Orinoco, rivers of the Guiana Shield, lower Solimões/Amazonas and upper Amazonas, which contributes to the remarkable ichthyofaunal diversity of the basin. A high rate of species endemism was observed in Characidae (24), Loricariidae (18), Cichlidae (18) and Callichthyidae (18), totalling 156 species (13.4%) endemic to the basin. An estimation of the species richness for the Rio Negro basin, considering 23 published references, resulted in 1,466 and 1,759 species (Jackknife 1 and 2, respectively), which seems reasonable when considering the large number of morphotypes left out of the present list and the low sampling effort in many areas of the basin. The results presented herein provide an additional tool for environmental managers and decision makers for conservation purposes of one of the richest and most well-preserved sub-basins of the Rio Amazonas system.
Using the most comprehensive fish occurrence database, we evaluated the importance of ecological and historical drivers in diversity patterns of subdrainage basins across the Amazon system. Linear models reveal the influence of climatic conditions, habitat size and sub-basin isolation on species diversity. Unexpectedly, the species richness model also highlighted a negative upriver-downriver gradient, contrary to predictions of increasing richness at more downriver locations along fluvial gradients. This reverse gradient may be linked to the history of the Amazon drainage network, which, after isolation as western and eastern basins throughout the Miocene, only began flowing eastward 1–9 million years (Ma) ago. Our results suggest that the main center of fish diversity was located westward, with fish dispersal progressing eastward after the basins were united and the Amazon River assumed its modern course toward the Atlantic. This dispersal process seems not yet achieved, suggesting a recent formation of the current Amazon system.
The ichthyofauna of the rio Purus has been little investigated, especially in its lower portion, characterized by diverse aquatic environments, especially in flooded areas. We inventoried the ichthyofauna of floodplain lakes with different management efforts in Reserva de Desenvolvimento Sustentável Piagaçu-Purus (RDS-PP), which represent important resource for commercial fishing in North region, in the first illustrated inventory of the fish fauna from lower rio Purus. We surveyed 20 lakes, classified as open access (eight lakes) and protected (12 lakes) during 2009 low water levels. A total of 2,299 individuals were collected, represented by seven orders, 25 families and 74 species. Characiformes was the most representative order in number of species and families, followed by Siluriformes, Cichliformes, Gymnotiformes, Clupeiformes, and Osteoglossiformes. Most abundant and frequent species were Pygocentrus nattereri, Triportheus angulatus, Serrasalmus sp. "2n=58", Pterygoplichthys gibbiceps, and Osteoglossum bicirrhosum. Protected lakes presented higher species richness compared to open access lakes. Similarly, protected lakes possessed 26 species occurring exclusively, with emphasis on Colossoma macropomum, an important species for fisheries due to its commercial importance. We added 44 new records of fish species for the lower rio Purus. Our results indicate the potential efficiency of zoning systems of open access and protected lakes established by local population and ruled by RDS-PP for fisheries management. Therefore, we strongly suggest its maintenance for conservation of ichthyofauna of floodplain lakes of lower rio Purus.
We provide a general compilation of the diversity and geographical distribution of Amazonian fishes, updated to the end of 2018. Our database includes documented distributions of 4214 species (both Amazonian and from surrounding basins), compiled from published information plus original data from ichthyological collections. Our results show that the Amazon basin comprises the most diverse regional assemblage of freshwater fishes in the world, with 2716 valid species (1696 of which are endemic) representing 529 genera, 60 families, and 18 orders. These data permit a view of the diversity and distribution of Amazonian fishes on a basinwide scale, which in turn allows the identification of congruent biogeographical patterns, here defined as the overlapping distributions of two or more lineages (species or monophyletic groups). We recognize 20 distinct distributional patterns of Amazonian fishes, which are herein individually delimited, named, and diagnosed. Not all these patterns are associated with identifiable geographical barriers, and some may result from ecological constraints. All the major Amazonian subdrainages fit into more than one biogeographical pattern. This fact reveals the complex history of hydrographical basins and shows that modern basin-defined units contribute relatively little as explanatory factors for the present distributions of Amazonian fishes. An understanding of geomorphological processes and associated paleographic landscape changes provides a far better background for interpreting observed patterns. Our results are expected to provide a framework for future studies on the diversification and historical biogeography of the Amazonian aquatic biota.
The Amazon basin houses a particular group of freshwater organisms, whose study tells the geological history of the region, how biological diversity was shaped, how it is maintained, and what it hides. The fish of the Amazon is represented by more than 3,000 known species distributed from the basal groups up to the more specialized ones. This species richness hides a diversity of adaptations that are dispersed at all levels of the biological organization. In this summary of the conference delivered at the Brazil-France Bilateral Symposium, held in Manaus in 2018, we describe two aspects of the hidden world of adaptive diversity: adaptations to changes in dissolved oxygen and the abilities of the Rio Negro fish to face acidic and ion-poor waters of their habitats. Also, we present the vulnerability of Amazonian fish to ongoing climate changes. Then, very briefly, we call attention to the many hidden biological processes that allow these fish species to survive their environments, much of which is unknown. Indeed, however, they are intricately related to men, either by responding to environmental disturbances that we have caused, or by containing information that contributes to improving the quality of the environment in which we live.
We analyzed the length‐weight relation (LWRs) of 14 species of fish, sampled in 30 sandy beaches along the Acre river, encompassing approximately 300 km of the river between the municipalities of Brasileia and Rio Branco, Acre state, Brazil, during the draught period in 2017 (August and September). For sampling, we used a picaré type trawl with 9 m of length, 2 m of height and 5 mm mesh between opposing knots, during the day and night periods. New information was made available for eight fish species.
The degradation of riparian vegetation in low-order streams can cause irreversible environmental damage, biodiversity loss and alter the structure of communities. In this context, the present study evaluated how the level of degradation of riparian vegetation influences the fish assemblage in three low-order streams in the Brazilian Amazon. In each stream, three different stretches were delimited, distributed in the environments of forest, edge and pasture, and the samplings were conducted in three hydrological regimes using dip nets. Influences of the stretches and streams on richness and abundance were tested with GLMM, on the composition with PERMANOVA and on indicator species with IndVal. Species richness was higher in forest environments and lower in pasture; while abundance was higher in pasture and lower in forest. Species composition differed between stretches, streams and in the interaction between stretches and streams, with a strong difference between stretches of forest and pasture environments. Six species dependent of the riparian vegetation were classified as indicators of forest environments; while a generalist species was indicator of pasture. These results reinforce the negative influence of riparian vegetation removal on biological communities and provide subsidies that can help in the conservation and management of these systems.
The obscure taxonomic histories of three species of Aphyocharax (A. alburnus, A. avary
and A. pusillus) are revised, based on both morphological and literature data. Aphyocharax
avary is resurrected as a valid species and removed from synonymy with A.
alburnus. Based on examinations of type specimens, A. alburnus is considered a junior
synonym of A. pusillus.