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1.
  1. Data on stranded sea turtles were examined between 2010 and 2016 along the northern region of Rio de Janeiro state and between 2016 and 2017 in the southern region, looking for spatio‐temporal patterns and determining which factors contributed to their mortality.
  2. A total of 12,162 strandings of all five species that occur in Brazil were recorded, with Chelonia mydas being the most common (89.9%). Sea turtles use the Rio de Janeiro coast as a feeding and/or migration area. The intense upwelling (October to April) may be an important factor for the sea turtles feeding in this region, mainly for Eretmochelys imbricata and Dermochelys coriacea, which had a higher number of strandings during this period.
  3. Areas further north of the study area include an important nesting site for Caretta caretta in Brazil, which explains the higher concentration of strandings of subadults/adults of this species in this region and during its nesting season.
  4. Many anthropogenic threats to sea turtles were documented, mainly incidental capture in fisheries and marine debris, indicating possible hotspots for these threats in the regions of Sepetiba and Guanabara Bays, Cabo Frio, and São Francisco de Itabapoana.
  5. Among the natural causes of strandings, the primary factors were chronic illness, endoparasites, and fibropapillomatosis. However, pollution may also be an indirect threat, which negatively affects these animals through reduced health and immunosuppression, leaving them more susceptible to opportunistic diseases.
  6. These data are valuable for directing and implementing specific and local mitigation measures along the Rio de Janeiro state coast, such as avoiding bycatch hotspots through fleet communication programmes and/or area and seasonal closures, enforceable legislation, effective penalties and proper waste management.
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2.
  1. Bivalves are important ecosystem engineers, and there is emerging evidence that many species are afflicted with castrating parasites. Understanding the prevalence of these largely overlooked parasites is crucial in understanding the fundamental biology of bivalves, informing conservation efforts, and providing a wider understanding of host–parasite dynamics.
  2. Current techniques to assess the presence of parasites are destructive, making them untenable for endangered or protected populations. This article presents a non-destructive method of sampling bivalve molluscs (Anodonta anatina) to detect castrating trematodes. Gonadal fluid is removed with a hypodermic needle from bivalves in situ and analysed in a laboratory setting without removing the mollusc from the field; this sampling mechanism has previously been shown not to harm the mollusc.
  3. A single 50 μl sample is sufficient to detect both the presence and developmental stage of the trematode with greater than 95% reliability, with all but the lightest infections visible. We recommend that this technique should be used to enhance knowledge on host–parasite dynamics in bivalves, and inform sensible conservation for threatened species.
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  1. Freshwater mussels (Order Unionida) are highly threatened. Interspecific competition for food sources with invasive alien species is considered to be one of the factors responsible for their decline because successful invaders are expected to have wider trophic niches and more flexible feeding strategies than their native counterparts.
  2. In this study, carbon (δ13C: 13C/12C) and nitrogen (δ15N: 15N/14N) stable isotopes were used to investigate the trophic niche overlap between the native freshwater mussel species, Anodonta anatina, Potomida littoralis, and Unio delphinus, and the invasive bivalve Corbicula fluminea living in sympatry in the Tua basin (south-west Europe).
  3. The species presenting the widest trophic niches were C. fluminea and A. anatina, which indicate that they have broader diets than U. delphinus and P. littoralis. Nonetheless, all the species assimilated microphytobenthos, sediment organic matter, and detritus derived from vascular plants, although with interspecific variability in the assimilated proportions of each source. The trophic niche of the invasive species overlapped with the trophic niche of all the native species, with the extent varying between sites and according to the species.
  4. From the three native species analysed, Potomida littoralis may be at a higher risk for competition for food with C. fluminea in the Tua basin, if food sources become limited, because this native mussel presented the narrowest trophic niche across sites and the highest probability of overlapping with the trophic niche of C. fluminea.
  5. Given the global widespread distribution of C. fluminea, the implementation of management measures devoted to the control or even eradication of this invasive alien species should be a conservation priority given its potential for competition with highly threatened native freshwater mussels.
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  1. Freshwater ecosystems represent less than 0.01% of Earth's surface water but proportionately encompass the most species-rich environment on the planet, including nearly one-third of all vertebrate species. Even though inland continental waters are widely regarded as highly endangered ecosystems, their species assemblages are mostly ignored in conservation plans, largely because spatial patterns of freshwater species remain poorly understood. This is particularly severe throughout the Neotropics, most notably in the Amazon superbasin, where the sheer biotic diversity is coupled with a severe lack of biodiversity knowledge at several levels.
  2. Spatial patterns of Neotropical freshwater fishes focusing mainly on the Amazon superbasin were investigated. First, Endemic Amazonian Fish Areas (EAFAs) representing central units for the conservation of continental fishes were delimited. Interpolated maps were then analysed using alternative methodologies to delimit spatial patterns of diversity and endemicity across the Amazon superbasin. Several biogeographical analyses used a comprehensive dataset of species and geographical coordinates of Amazonian fishes.
  3. The results reveal well-defined spatial patterns of species richness and endemicity in the Amazonian fish fauna, showing that most protected areas are concentrated in a single bioregion (Amazon lowlands). Those areas are incongruent and insufficient to protect endemic and threatened species, which are mostly distributed in upland regions.
  4. Effective conservation of the Amazonian fish fauna should include EAFAs within protected areas, especially those undergoing deforestation and hydropower development pressure and containing a high concentration of threatened species.
  5. The following EAFAs should be considered as conservation priorities: Upper Araguaia, Upper Tocantins, Lower Teles Pires/Serra do Cachimbo, Chapada dos Parecis and Upper Marañon. These regions should be urgently protected to avert the loss of important trophic relationships and unique elements of the Amazonian fish fauna.
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8.
  1. Human activities are an increasing threat to Neotropical freshwater ecosystems, with the potential extinction of thousands of aquatic species. Despite this, knowledge about the effectiveness of protected area networks in protecting aquatic insects in this biogeographical region is very limited.
  2. Cuba supports the highest diversity of aquatic insects in the Antilles, with a large number of endemics.
  3. A gap analysis was conducted to assess the effectiveness of the National System of Protected Areas of Cuba (NSPAC) in the conservation of Cuban diving beetles (family Dytiscidae). This involved considering the areas with the highest potential species richness, estimated by using species distribution models with three different approaches (MaxEnt, Random Forest and Support Vector Machine), and the known localities of endemic species.
  4. The highest potential species richness of Dytiscidae in Cuba is predicted to occur in the low–medium altitude of the eastern mountain areas. Although most of these areas occur inside the NSPAC, several areas of potential high species richness are currently unprotected. It is recommended that sampling programmes are carried out in areas with high predicted species richness to validate the species distribution models.
  5. The distribution of three Cuban endemic species (Copelatus barbouri, Desmopachria glabella and Celina cubensis) lies completely outside of the NSPAC. Despite their conservation interest as threatened endemic species, they are currently unprotected.
  6. To improve the conservation of freshwater biodiversity in Cuba it is recommended that (i) the NSPAC network is extended to protect areas supporting endemic species and those with the highest potential species richness that are currently unprotected, and (ii) a whole-catchment management approach, specifically to maintain natural flows, should be adopted, especially in the mountainous areas of eastern Cuba.
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  1. Commodity-driven forest conversion represents one of the most severe threats to freshwater biodiversity in Southeast Asia, notably causing population declines and the extinction of freshwater fish species.
  2. Although a variety of freshwater taxa are likely to be adversely affected by forest conversion, little is known about the impact on ecologically and economically important invertebrates such as decapod crustaceans.
  3. This study evaluated the impact of forest conversion and land-use change on freshwater Macrobrachium shrimp species, using species richness, abundance, and environmental data collected from 20 streams across southern Peninsular Malaysia. Streams were located in three types of landscape: forest; oil palm plantation; and mixed land use, comprising young secondary forest, small-scale plantations, patches of open and sparsely vegetated areas, and agricultural fields and clearings.
  4. Generalized linear models showed that even incomplete change from forest habitats to mixed land use and oil palm plantation resulted in significantly lower Macrobrachium native species richness and higher non-native species abundance. Native species richness was positively correlated with canopy cover, leaf litter, substrate size, and dissolved oxygen, and was negatively correlated with water temperature and conductivity. Native species richness was also negatively correlated with non-native species abundance, with non-native species abundance increasing along the human disturbance gradient.
  5. These results highlight the need for riparian habitat protection to conserve native Macrobrachium and limit the spread of non-native species. A management priority should be to maintain or restore optimum instream habitat conditions for shrimps, which would also benefit fish and other benthic macroinvertebrates. Suitable riparian management requires substantial support and funding from multiple stakeholders, but it can be aligned with other catchment-based strategies to optimize the use of limited resources available for freshwater biodiversity conservation.
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  1. Climate change is causing shifts in the distribution patterns of freshwater fish at various spatio-temporal scales. Tropical freshwater fish are vulnerable, especially in areas where a high impact of climate change is predicted; thus, there is an increasing need to predict these shifts to determine conservation and adaptation strategies.
  2. Ecological niche models offer a reliable way to predict the effects of climate change on species distribution. Potential shifts in the distribution of tropical fish were tested under two scenarios (4.5 – moderate and 8.5 – extreme) with three general circulation models for years 2050 and 2070 using maximum entropy software using as models two predatory species – the tropical gar Atractosteus tropicus and the giant cichlid Petenia splendida.
  3. The potential distribution of both species was associated with warm and humid–sub-humid conditions. Future projections showed a higher availability of suitable areas for both species resulting from the expansion of warmer conditions in the middle and upper basins of the Central American mountain range and centre of the Yucatan Peninsula.
  4. Ecological niche models of keystone or umbrella species such as A. tropicus and P. splendida could be useful to support conservation plans of protected areas. The potential distribution of both species covers areas of high suitability including six important biosphere reserves in Mexico, three protected areas in Guatemala and part of the Mesoamerican biological corridor.
  5. Despite the potential expansion of the present distribution range suggested by the models, it is important to consider the biological and ecological requirements of the species and the ecological implications of these potential shifts in distribution. Both scenarios could have several implications at genetic, population, and ecosystem levels.
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  1. Freshwater ecosystems, providing valuable goods and services to humans, have been subjected to multiple human impacts, among which climate change plays a central role in threats to species. It is expected that protected areas, the cornerstone of biodiversity conservation efforts, will assume a decisive role in protecting freshwater species from the impacts of climate change.
  2. This study assessed the effects of climate change on migratory fish of the second largest neotropical river basin, evaluating the effectiveness of protected areas in safeguarding fish species, and hence the ecological functions that they perform and the ecosystem resources that they provide. The present range of 23 migratory fish of economic interest in the Paraná–Paraguay basin was estimated and the responses to future climatic shifts projected to the middle and end of the 21st century were examined, quantifying predictive uncertainties.
  3. Changes and losses of climatically suitable areas will trigger severe contractions in range, with the greatest impact on the most valuable species in commercial fishing, where range losses are likely to surpass 65% in the future. The main channel of the Upper Paraná River and tributaries of its left margin are projected to serve as climatic refuges for many species, and such regions are not affected by high predictive uncertainty. The results revealed that protected areas do not sufficiently protect migratory fish at present, and that they will continue to offer negligible protection in the face of climate change.
  4. This study alerts decision makers to the potential damage to inland fishery resources from climate change and provides useful information to guide conservation strategies spatially. We advocate that the creation of new protected areas and the redesign of the existing network to encompass regions that maximize current and future occupancy of migratory fish are crucial to conserve the valuable ecological, societal, and economic benefits that they provide.
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  1. Despite the current rates of deforestation and the expected climatic changes, protecting species in their natural habitats is still the simplest, cheapest, and most effective way of safeguarding biodiversity. Here, the network of protected areas in the Brazilian Amazon was evaluated to assess its effectiveness in safeguarding species of Odonata.
  2. Ecological niche models were built to assess the suitability of the habitat for 503 Amazonian odonate species. Then, the effectiveness for the protection of odonate species of three classes of protected areas (strictly protected area, sustainable use area, and indigenous territory) was evaluated.
  3. Approximately 30% of the species are protected within the network of protected areas. These findings highlight the importance of protected areas for safeguarding most odonate species in the Amazon. For under-represented or gap species, additional resources are still needed for effective management and protection on some private properties, which need to set aside land for conservation. In this way, it is possible to preserve habitats for odonate species and guarantee their conservation in the Amazon.
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17.
  1. Conservation of riverine fish often aims to improve access to spawning grounds and restore longitudinal connectivity by removing migration barriers, and involves substantial investments. However, these investments also enable non‐native predators to invade upstream into spawning areas and potentially adversely affect the recruitment of threatened freshwater fish through egg or fry predation.
  2. Detecting egg predation is often challenging. Visual inspections of fish gut contents may underestimate predation of soft materials such as eggs and fry, which limits the discovery of predators preying upon these life‐stages. DNA‐based detection assays may offer a more sensitive tool to assess predation of soft materials.
  3. A conservation issue was confirmed by developing and applying a species‐specific DNA‐based detection assay: invasive round goby (Neogobius melanostomus) prey on the eggs or fry of the threatened common nase (Chondrostoma nasus) in Switzerland.
  4. DNA‐based detection assays were also developed for five other valuable native fish species, including endangered salmonid and cyprinid river spawners. The applicability of the assays was confirmed in a series of laboratory and field feeding experiments involving eggs and fish tissue. In addition, this work provides a guiding framework for conservation managers regarding the use and applicability of different DNA‐based detection approaches for gut content analysis.
  5. The results of this study could inform local conservation measures – such as temporary reductions in the density of round goby at spawning sites prior to spawning – and demonstrate how targeted application of species‐specific molecular markers may advance freshwater fish management.
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18.
  1. The Amazon Basin is being degraded at unprecedented rates, yet conservation efforts have implemented protected areas to curb deforestation, leaving freshwater ecosystems vulnerable to degradation. Amazon freshwater ecosystems are largely unprotected because a terrestrial bias has limited the ability of science to affect policy.
  2. Overcoming this bias requires increasing exchange of information among stakeholders across the basin to raise awareness of threats to Amazon freshwater ecosystems and promote discussions and access to conservation solutions. To help address this need, this Special Issue collates 15 synthetic articles that advance knowledge and identify conservation solutions.
  3. Three articles highlight the importance of considering the hydrological and limnological processes that control the integrity of these freshwater ecosystems and offer new insights on how to extrapolate them across the basin.
  4. Three articles on crocodilians, aquatic mammals, and migratory fishes document threats and knowledge gaps, and identify the missing role of governments as an impediment to conservation of their populations.
  5. Three articles evaluate the multi-faceted effects of hydropower dams on fish, birds, and floodplain trees. They reinforce perceptions that dams are key environmental threats and offer guidance for improving protocols for dam site selection and impact assessment.
  6. Three articles assessing the effectiveness of protected areas to safeguard fish and aquatic invertebrates show there is an urgent need to redesign the Amazon protected area network to adequately protect freshwater biota.
  7. Three forward-looking articles show that: (i) conservation initiatives by local communities are ‘bright spots’ for freshwater conservation; (ii) microchemistry analyses of the ear bones of fishes could boost the knowledge base needed to conserve them; and (iii) strengthening the Amazon conservation framework requires a reversal of Brazil's current governmental priorities, remobilization of stakeholders, investments in capacity building, and expanding protections to terrestrial and freshwater ecosystems.
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19.
  1. The Amazon basin hosts the Earth's highest diversity of freshwater fish. Fish species have adapted to the basin's size and seasonal dynamics by displaying a broad range of migratory behaviour, but they are under increasing threats; however, no study to date has assessed threats and conservation of Amazonian migratory fishes.
  2. Here, the available knowledge on the diversity of migratory behaviour in Amazonian fishes is synthesized, including the geographical scales at which they occur, their drivers and timing, and life stage at which they are performed.
  3. Migratory fishes are integral components of Amazonian society. They contribute about 93% (range 77–99%) of the fisheries landings in the basin, amounting to ~US$436 million annually.
  4. These valuable fish populations are mainly threatened by growing trends of overexploitation, deforestation, climate change, and hydroelectric dam development. Most Amazonian migratory fish have key ecological roles as apex predators, ecological engineers, or seed-dispersal species. Reducing their population sizes could induce cascading effects with implications for ecosystem stability and associated services.
  5. Conserving Amazonian migratory fishes requires a broad portfolio of research, management, and conservation actions, within an ecosystem-based management framework at the basin scale. This would require trans-frontier coordination and recognition of the crucial importance of freshwater ecosystems and their connectivity.
  6. Existing areas where fishing is allowed could be coupled with a chain of freshwater protected areas. Management of commercial and subsistence species also needs fisheries activities to be monitored in the Amazonian cities and in the floodplain communities to allow assessments of the status of target species, and the identification of management units or stocks. Ensuring that existing and future fisheries management rules are effective implies the voluntary participation of fishers, which can be achieved by increasing the effectiveness and coverage of adaptive community-based management schemes.
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20.
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