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

Shallow coastal habitats are ruled by fluctuating environmental conditions, which lead to shifts in fish communities. Functional groups of habitat use and trophic strategy were used to address the responses of fish composition and diversity, since comparisons of rich tropical systems are often complex through species-based approaches. We hypothesized that fish groups will have specific affinities in response to the prevailing environmental conditions, especially those reflecting the prevalence of oceanic or estuarine conditions, where guilds of habitat use would perform better as indicators. Despite the importance of other environmental factors (i.e. temperature and transparency), salinity was the key structuring factor irrespective of the coastal lagoon. Although harbouring the greatest biomass of piscivores, the harsh environmental conditions at Araruama lagoon were related to low diversity. A great number of indicator species, typically of marine affinity, was found at the Saquarema lagoon, probably due to the continuous and broad connection to the sea leading to the predominance of euhaline conditions. Despite the presence of non-native species (i.e. Oreochromis niloticus), the Marica lagoon function as an important refuge for freshwater groups. Our results stressed the key role played by coastal lagoons of varied water conditions in supporting fish diversity at regional levels.

Besides human health risks, phycotoxins may cause physiological injuries on molluscan shellfish and, consequently, damages to marine ecosystems and global fisheries production. In this way, this review aimed to present an overview of HABs impacts on marine shellfish by evaluating the effects of cultivated molluscs exposure to microalgae and cyanobacteria that form blooms and/or synthesize toxins. More specifically, it was assessed the main molluscan shellfish responses to harmful algae, trophic transfer and dynamics of phycotoxins, and the risks for human health. Of the 2420 results obtained from literature search, 150 scientific publications were selected after thorough inspections for subject adherence. In total, 70 molluscan species and 37 taxa of harmful algae were assessed from retrieved scientific publications. A significant positive correlation was found between the marine production of molluscs and the number of available studies by molluscan category. Molluscan responses to HABs and phycotoxins were categorized and discussed in three sub-sections: effects on grazing and behavior, metabolic and physiological reactions, and fitness consequences. The main histopathological injuries and toxin concentrations in molluscan tissues were also compiled and discussed. Bivalves often accumulate more toxins than gastropods and cephalopods, occasionally exceeding recommended levels for safe consumption, representing a risk for human health. Harmful algae impact on molluscan shellfish are complex to trace and predict; however, considering the perspective of increase in the occurrence and intensity of HABs, the intensification of efforts to expand the knowledge about HABs impacts on marine molluscs is crucial to mitigate the damages on economy and human health.

Intraspecific variation in thermal tolerance can favor species persistence in a warmer ocean, but is often over-looked in fine-scale studies. Nonetheless, local drivers (e.g. salinity) interact with temperature to shape species' thermal response. Here, we acclimated juveniles of Brazilian silversides Atherinella brasiliensis captured at the limits of a marine-estuarine ecocline under reciprocal-cross conditions, to test for phenotypic plasticity in heat tolerance. We also tested whether silversides acclimated to temperatures predicted for 2100 (+3-4.5 degrees C). Fish in warm-brackish waters showed higher CTMax (Critical Thermal Maximum) than those in cold-marine conditions, regardless of their origin. Silversides' CTMax reached up to 40.6 degrees C, but it did not increase after exposure to temperatures predicted for 2100. Lack of acclimation response suggests that silversides heat tolerance has reached a "ceiling", despite thermal plasticity. Our findings show that fine-scale environmental heterogeneity can promote phenotypic plasticity for tropical species, reducing the risk of short-term extirpation. 140961/2019-4 info:eu-repo/semantics/publishedVersion

Ceratium furcoides is a freshwater dinoflagellate originally from cold waters of northern Europe that has been expanding its distribution into new areas worldwide. Species distribution modeling (SDM) based on maximum entropy algorithm (MaxEnt) showed that C. furcoides has a much wider potential range than its current distribution and isothermality as the key environmental variable determining its spatial pattern. The model successfully predicts areas of introduction and the climate matching approach has identified mainly tropical and some subtropical regions as most vulnerable areas at risk of introduction and establishment of C. furcoides. Furthermore, the observed shift of the climatic niche occurred between native and non-native ranges, providing, for the first time, a robust evidence that a dinoflagellate can occupy climatically distinct niche spaces following its introduction into new areas. This is probably mirroring the lack of adequate management to deal with various impacts on drainage basins, such as ongoing accelerated cultural eutrophication coupled with river impoundments and water diversion. Thus, this framework provides helpful insights on how to optimize our ability to anticipate invasions and to avoid ecosystem services losses, as well as future studies prospects on adaptive mechanisms of this pervasive invader.

This study aimed to address the Ophiothela species distribution worldwide, report invasive populations, and investigate their association with benthic organisms through an extensive review of the scientific literature. All six Ophiothela species occur between latitudes 33o S and 38o N and, together, are dispersed across 75% of the marine realms. Spread throughout more than 6700 km of the Western Atlantic Ocean coastline, O. mirabilis is the only species recorded as invasive. Higher plasticity in substrate use was detected in invaded areas than in native ones, which indicates that substrate availability does not limit the invasive potential of O. mirabilis. The colonization affinity of Ophiothela species is high for Cnidaria species, irrespective of population origin. High densities (e.g., up to 2.8 brittle stars cm−2 per gorgonian surface) and opportunistic habitat colonization pattern found for O. mirabilis invasive populations suggest fast dispersion rates along the Atlantic coast. Therefore, the expansion of this species to nearby systems is likely, and the potential to damage native host species is high.

The intermediate disturbance hypothesis (IDH) has been thoroughly investigated, but much controversy has been found for supporting its assumptions, which rely largely on the nature of the disturbance, spatial scale, and biological predictors tested. In this paper, richness of native and non-native species along a suite of Neotropical aquatic ecosystems across a broad latitudinal and geographical range was used to test the IDH predictions. An extensive literature survey was performed to compile native species richness and the occurrence of several taxonomic groups listed as non-native for twenty-four coastal rivers and bays evenly distributed into three climatic zones (tropical, transitional, and subtropical). The climatic gradient was confirmed by NMDS and PERMANOVA, but IDH predictions were only significantly supported for native and total species richness in the coastal bays. The distribution patterns of non-native marine species showed a linear instead unimodal pattern of increase with latitudinal climatic gradient, but the responses are complex and dependent of many non-exclusive factors, such as the sampling effort per ecosystem and the potential interference of other disturbance gradients that should be further addressed to unravel the role of IDH for non-native species distribution.

Disentangling multilevel sources of variation is critical for understanding of diversity patterns in high-variability environments. We investigated the scale sensitivity of short-term environmental effects on the temporal beta diversity of fishes in 3 tropical coastal lagoons in Southeastern Brazil. Environmental effects were investigated at 3 hierarchical levels (local, zone, and lagoon). An AICc-based model selection was applied to generalized linear mixed models relating abundance-based beta diversity (Bray-Curtis dissimilarity; βBC) to environmental distances and random effects for other sources of variability. Abundance gradients (βBC-GRA) contributed more for βBC at all hierarchical levels, most likely due to random changes in the abundances of numerous rare marine-origin species. The temporal and spatial marine influences favored the balanced variation in the abundance of different species (βBC-BAL), probably by allowing for marine species with different environmental tolerances and requirements. The freshwater vs. marine influences were primarily represented by short-term effects of salinity changes at the local and zone levels and tide height and accumulated rainfall at the lagoon level. Other environmental effects (e.g. pH and transparency) were representative of that balance depending on the βBC component and hierarchical level. Random effects for morphometric features (local level, width of the connections between zones; lagoon level, distance from the ocean) and climate-related factors (local and zone levels, wind intensity and accumulated rainfall; lagoon level, changing seasons) were also relevant for the relationships between environmental variability and βBC. This study evidenced major scale-related mechanisms driving the temporal beta diversity of fishes in tropical coastal lagoons.

Syntopic species with similar anatomic configuration may face strong competition for trophic resources, thus relying on developed mechanisms to ensure coexistence. The present study investigated the influence of body size on trophic interactions between juveniles of two closely related fish species at three sandy beaches in south-eastern Brazil. A total of 150 fish were sampled, where 103 were identified as Trachinotus carolinus (mean ± SE: weight = 9 g ± 1.13) and 47 as Trachinotus goodei (weight = 46.7 g ± 3.34). A significant size-difference between juvenile Trachinotus was detected by a null-model analysis (P = 0.04), with T. carolinus (TL = 79.6 mm ± 2.4) presenting a smaller body size than T. goodei (TL = 147.7 mm ± 4.2). The main prey items consumed by T. carolinus were Perna perna (IAi = 0.76) and Emerita brasiliensis (IAi = 0.18), whereas the latter was the major T. goodei dietary prey (IAi = 0.71). Both prey were correlated with larger-sized juveniles of each pompano species, whereas smaller fish shared non-preferred trophic items. Such opportunistic behaviour of smaller juveniles may account for the dietary overlap detected between the Trachinotus species (P = 0.09). Size-related dietary partitioning was observed for the largest T. goodei juveniles, which displayed only a slight overlap with T. carolinus, and between juveniles belonging to the small and medium size groups of each pompano species. Therefore, food partitioning related to pompano body size seems to be especially important for the smallest juveniles, as they present the highest vacuity (particularly T. carolinus) in the sampled beaches, suggesting that these individuals are under intra- and interspecific competitive pressure, which may affect local coexistence.

Global inland water biodiversity is under mounting stress facing future scenarios of climate change, biological invasions, pollution, diversion, damming of rivers, and increase of water abstractions. Apart from having isolated effects, all these stressors threats act synergistically and thus pose additional emerging threats to biodiversity and ecosystem services. Native to Northern Europe, the nuisance and potential toxic dinoflagellate Ceratium furcoides (Levander) Langhans 1925 is a silent invader that blooms in freshwater systems; it has one of the most rapid spread rates globally. We propose a framework to determine the worldwide most vulnerable areas for the invasion by C. furcoides shortly (2041-2060) by combining future scenarios of climate change (a proxy for invasiveness) derived from ecological niche models with future dam construction data (a proxy for invasibility). The nine models applied in four future scenarios of greenhouse gas emission from Coupled Model Intercomparison Project Phase 6 showed a general increase in areas suitable for the invasion success of C. furcoides. High susceptibility overlapped with areas densely occupied by large and medium-size dams and future dam construction projects. Considering that C. furcoides can reproduce from a single cell, produces resistant stages, and has several strategies to cope with local environmental constraints, early detection protocols, and mitigation actions are urgently needed to avoid biodiversity declines related to this invader.

Guanabara Bay (GB) is a highly contaminated estuarine system and an important fishing area in Southeastern Brazil. In this regard, knowledge concerning the association of certain contaminants in seafood to abiotic factors and human health risk assessments is still understudied. Therefore, this study aimed to quantify nine toxic elements in highly consumed crabs, shrimp, and squid, and associate the results with abiotic factors. A human health risk assessment was also performed. Our findings indicate that crabs are the main bioaccumulators. Transparency and depth were noteworthy for all three taxonomic groups. In general, contaminant concentrations were below the limits established by different international agencies, except for As, which was higher than the Brazilian limit (1 mg kg

False mussels are recognized as the brackish water equivalent of zebra mussels, although the abiotic and habitat conditions that mediate these invaders’ success are barely known. In this context, we aimed to evaluate the native and non-native geographical distribution of Mytilopsis species worldwide and assess biological traits, environmental condition, and habitat associated with false mussels in native and invaded systems. Our hypothesis is that Mytilopsis invasion is driven by species plasticity to environmental conditions and substrate use in brackish systems, where the colonization of non-native populations is favored by great availability of artificial substrates and tolerance to wide ranges of environmental conditions. Besides, this study provides the occurrence range and distribution patterns of Mytilopsis species within their introduced and native areas and tracks the spread of introduced populations worldwide. Considering the five species evaluated, M. leucophaeata and M. sallei are the most widespread, while M. adamsi, M. trautwineana, and M. africana showed more restricted geographic distribution. In the last decades, M. leucophaeata and M. sallei consolidated and expanded their distributions. Environmental conditions were significantly different between native and non-native areas, where Mytilopsis populations presented significantly higher densities. Non-native populations exhibited remarkable plasticity concerning habitat colonization that was more frequent on artificial substrata. Mytilopsis populations presented significant differences on their biological traits, habitat environmental conditions, and substrate use between native and non-native areas. These species seem to adapt to the conditions of invaded systems, changing their preferences, which reflects plasticity and suggests a potential shift of their realized niches.

Cymothoids are ectoparasites that may attach to various parts of the fish for molting and reproductive purposes, thus increasing the energetic costs of the host. This study investigated the influence of the parasitic isopod Mothocya nana on the physiological condition and diet of adult Brazilian silversides Atherinella brasiliensis at a sandy beach in southeastern Brazil. We collected 268 A. brasiliensis individuals, of which 230 fish were non-parasitized (mean ± SE total weight [TW] = 16.92 ± 0.38 g; total length [TL] = 127 ± 0.88 mm) and 38 were parasitized by up to 2 isopods (TW = 15.89 ± 0.79 g; TL = 126 ± 1.96 mm). Parasitic prevalence (P) and intensity (I) reached highest values in June 2015 (P = 20.88%; I = 1.31) and were slightly higher on males (P = 17.39%; I = 1.33) than on females (P = 13.07%; I = 1.27). Parasitized fish revealed poorer condition than non-parasitized ones, among which male hosts were especially burdened by M. nana's attachment. The condition factor, the eviscerated condition factor and the fullness index each showed a decreasing trend according to the parasite's development and offspring weight (i.e. increase in egg and larval weight). Parasitized and non-parasitized Brazilian silversides fed mainly on microcrustaceans, but the first group showed reduced phytoplankton intake and was associated with fewer trophic categories in comparison to non-parasitized fish. These dietary shifts revealed correlation with the poorer physiological condition reported for infected A. brasiliensis, whose decreased feeding efficiency is likely related to potential impairment of the filter-feeding mechanism and/or altered behaviour due to pressure atrophy and the increased energetic costs imposed by M. nana's development.

Voluntary participation of citizens scientists has become a valuable tool for scientific research, but rarely applied for detection of non-native species in marine environments. This study was conducted in the Rio de Janeiro state, southeastern Brazil, at sites used for the SCUBA diving. The awareness activity was directed at dive centres before dives, addressing themes such as marine biodiversity, rocky reefs, biological invasions and citizen science. After the briefing, divers were invited to record occurrences of the invasive Tubastraea spp. on a wet note slate that were left under the responsibility of the dive centers, usually visible on the boat. This study showed a high level (100%) of credibility for data provided by volunteers, new records (N = 39) for the invasive species that had not previously been mentioned in published articles, and that the approach used is efficient in its spatial and temporal aspects. The successful development of citizen-based monitoring programs depends on the approximation of the academic community and the commitment of dive operators. The diver plays a critical role within this process, providing valuable information, which can be used to confirm the engagement of common citizens and also to track the spread of non-native marine species.

Peacock bass Cichla ocellaris is a piscivorous cichlid native from the Amazon and Orinoco river basins, which has been broadly introduced into tropical areas worldwide, leading to several adverse local effects. However, predictors of its invasibility and assessments of its ecological impacts over large spatial scales are still lacking. The importance of different environmental factors in explaining the relative abundance of peacock bass in 62 sites across South America (30 native and 32 invaded systems) was investigated. The impacts of peacock bass on fish assemblages were appraised, using years since introduction as a proxy of its cumulative impacts and modern statistical techniques, such as random forests, and negative binomial regression models. Random forests highlighted maximum depth, introduced status, and ecosystem type as the best predictors of the peacock bass relative abundance, which ranged 0.01–26.0%, increased with maximum depth, was highest in invaded reservoirs but decreased with depth in native riverine populations. Other factors such as climate or limnological features were less important in explaining C. ocellaris abundance, which did not vary markedly with years since introduction. Introduction year was not related to latitude but varied among hydrographic regions, indicating invasion pathways not linked to geographical proximity. Variation partitioning of different fish assemblage metrics showed that hydrographic region followed by limnological and reservoir features accounted for most explained variation, indicating a strong historical and local influence. Introduction time accounted for 5–8% of variation in species composition and diversity, independently of limnological features. Our results suggest that the ecological effects of introduced C. ocellaris on native fish fauna are likely but small compared to large geographical and environmental gradients. Although experiments and before-after designs are probably more sensitive in detecting the ecological impacts of invasive species, large-scale compilations of available data are more feasible and can provide invaluable information, especially for large-sized invaders that are often illegally introduced.

BPA is chemical pollutant of very high concern due to its toxicity to the environment and risks for human health. Environmental concern consists in BPA entrance into aquatic ecosystems due to acute and chronic toxicity to invertebrates and vertebrates. This study aimed to determine acute BPA toxicity to tropical estuarine-marine species of four trophic levels and integrate BPA toxicity values using species sensitivity distribution (SSD) analysis. Our hypothesis is that BPA toxicity increases towards higher trophic levels. Microalga (Tetraselmis sp.), zooplanktonic grazer (Artemia salina), deposit-feeder invertebrate (Heleobia australis), and omnivorous fish (Poecilia vivipara) were chosen as experimental models. Tetraselmis sp. showed the highest BPA tolerance, without a concentration-dependent response. Species sensitivity have increased from A. salina (LC50,96h = 107.2 mg L−1), followed by H. australis (LC50,96h = 11.53.5 mg L−1), to P. vivipara (LC50,96h = 3.5 mg L−1). Despite the toxicity hierarchy towards trophic levels, which partially supported our hypothesis, SSD did not evidence a clear pattern among estuarine-marine trophic groups. Our study disclosed the sensitivity of not yet investigated species to BPA and, in an integrative way, highlighted BPA toxic effects at different trophic levels. Although estimated acute hazardous concentration (HC5 = 1.18 mg L−1) for estuarine and marine species was higher than environmentally relevant concentrations, sublethal adverse effects induced by BPA exposure may lead to unbalances in population levels and consequently affect the ecological functioning of tropical coastal systems.

(1) Although suffers from intense pollution inputs, Guanabara Bay, the most socioeconomically and environmentally important estuary in Rio de Janeiro, Brazil, is still home to a diverse fauna, including several fish and crab species consumed by humans. The bay presents high sedimentation rates and sediment contamination, further aggravated by dredging processes carried out in recent years. In this context, this study aimed to verify the effect of the dredging process on total mercury (THg) concentrations at Guanabara Bay through swimming crab assessments sampled before (2016), during (2017), and after (2018) the dredging process, and mainly, if the detected concentrations can be harmful to consumer health, (2) Methods: Swimming crab samplings were carried out at the same time and sampling points in 2016, 2017 and 2018 and the total Hg was determined using a Direct Mercury Analyzer (DMA-80, Milestone, Bergamo, Italy), (3) Results: Increased Hg concentrations were observed during the dredging process, decreasing to lower values, close to the initial concentrations, at the end of the process. Some of the investigated abiotic factors favor Hg dynamics in the aquatic environment, while others were positively altered at some of the assessed sampling areas at the end of the dredging process, (4) Conclusions: Although crab Hg levels were below maximum permissible limits for human consumption, it is important to note that these animals are significantly consumed around Guanabara Bay, which may lead to public health issues in the long term.

The present study describes the community diversity and gives a seasonal distribution of an intertidal macroalgal assemblage at Prainha Beach, Arraial do Cabo City in Rio de Janeiro state, Brazil. Sampling was performed during four seasons of a 1-year period. Organisms were sampled and photographed using photoquadrats to quantify relative coverage. Ninety-six taxa of macroalgae were registered, including 23 chlorophytes, 19 ochrophytes, and 54 rhodophytes, while three barnacles, seven mollusks, one isopod, and one polychaete were recorded among the zoobenthos. In the upper intertidal zone, the coverage was frequently dominated by invertebrates. Macroalgae always dominated the middle and lower zones, covering almost 100 % in both zones. The highest values of species diversity (H’), richness (S), and turnover rates were found during the transition from spring to summer, which coincided with the upwelling period. A comparison with the 1980’s flora revealed that the major changes in the macroalgal assemblage were among species belonging to the same genera, unless new additions were provided. The combination of photoquadrats and minimally destructive sampling allowed a detailed description of the composition and structural characteristics of the intertidal zone, a methodology that should be applied to study protected marine areas.

The dark false mussel Mytilopsis leucophaeata occurs as non-native species in Asia, Europe and South America. Despite the low population density usually found in its native range, M. leucophaeata forms dense clusters in newly invaded areas which lead to impacts on local organisms and environment. Some of the impacts of non-native species on newly colonized areas may be positive. However, despite the empirical evidences of increase in water transparency by freshwater dresseinids, the hypothesis that dark false mussel enhances the quality of brackish water has never been tested so far. Thus, the present study aimed to determine M. leucophaeata impacts on the water quality of a nutrient-enriched coastal lagoon by (1) analyzing a historical water dataset for pre- and post-invasion at Rodrigo de Freitas Lagoon (Brazil) and (2) experimentally testing dark false mussel direct effects on water quality. Historical field data evidenced significant lower phytoplankton abundance and chlorophyll a, and higher water transparency for the post-invasion period. These pattens were also supported by time-series analyses, which detected a decreasing trend for total coliforms density and an increased trend for dissolved oxygen over time. Moreover, time series indicated a gradual increase in lagoon water level with time, but none or minor changes were evidenced for floodgates operation routine, meteorological variables, and the frequency of sewage input. In microcosms, M. leucophaeata was effective to increase water transparency and decrease E. coli densities. The combination of field and laboratory data partially supported the hypothesis that M. leucophaeata invasion promoted an improvement in lagoon water quality, but increased phosphorus availability through excretion in microcosm assays. Management of dark false mussel populations seems to be a potential strategy for water quality improvement within already invaded systems where high sewage-enriched effluents are released. However, as non-native species often unbalance ecological relationships and functioning of the invaded ecosystems, new introductions of M. leucophaeata must be avoided.

Sharpnose sharks Rhizoprionodon lalandii and R. porosus are frequently captured in fishing activities in Brazil and are significantly consumed by humans, especially in southeastern Brazil. Both species lack population data and suffer intense fishing pressures and habitat degradation, consequently hindering adequate management and conservation actions. In this context, this study aimed to assess mercury (Hg) contamination in R. lalandii, and R. porosus sampled off the coast of Rio de Janeiro, addressing both animal health and public health risks. Sharks were obtained from two artisanal fishing colonies in southeastern Brazil (Copacabana and Recreio dos Bandeirantes), located on the coastal zone adjacent to Guanabara Bay, one of the most important, productive, and contaminated estuaries in Brazil, and a further three artisanal fishing colonies from the Regia˜o dos Lagos area (Saquarema, Cabo Frio and Rio das Ostras). Hg concentrations in liver, muscle, and brain in R. lalandii (n ¼ 24) and R. porosus (n ¼ 20) specimens were determined by inductively coupled plasma mass spectrometry. A gravid female measuring 112 cm from Copacabana is the first record for an individual of this size for R. lalandii. No correlation between length and muscle Hg concentrations was observed, and no differences between Hg concentrations for muscle or liver were found between male and female juveniles from either Cabo Frio or Rio das Ostras. No differences in Hg loads were observed herein for both assessed species. Low Hg bioaccumulation in juveniles and nongravid female muscle tissue was noted compared to significantly higher Hg concentrations in gravid females. Hg was detected in all embryos, indicating potential maternal offloading. As Hg thresholds for sharks in particular have not yet been established, whether the Hg concentrations detected in brain pose neurotoxic risks for these animals is not known. Public health concerns concerning adult R. lalandii consumption from Copacabana, however, are significant.

Guanabara Bay is located within one of the most populated areas in Brazil, still harbouring a great aquatic biodiversity and supporting important commercial fisheries despite the increased levels of human disturbances. Here, individual and simultaneous effects of water temperature, pH, and salinity on reef-associated and transient fish assemblages in a transitional marine-estuarine zone of Guanabara Bay were addressed. It was predicted that composition and structure of fish assemblages will respond differently to these environmental variables, depending on the species-specific degree of association with rocky substrates. A canonical correspondence analysis applied on all 83 fish species caught revealed that fish assemblages as a whole were mainly driven by salinity and pH, but with no clear trend of species association or seasonal responses. Canonical analysis of principal coordinates revealed a group composed only by reef-associated species, which was separated from a second group of only transient species, but some species of overlapping distribution were also detected (mixed group). Reef-associated species followed mostly a salinity gradient, whereas transient species responded to salinity and temperature, and those of the mixed group were ruled by salinity and pH. Generalized additive models indicated that, except for transient species, fish richness increased with the effects of estuarine waters from inner bay. Our study is the first to highlight the importance of a transitional zone in coastal bays, which can apparently increase the potential of sharing species among marine and estuarine areas, leading thus to positive effects on local biodiversity. We also stress the role of salinity as key structuring factor of the fish assemblages in tropical coastal bays, and its potential to be used, in conjunction with pH and temperature, as a proxy of alternating influence of estuarine and oceanic waters in these systems.

In this paper, the diet and trophic structure of fish assemblages caught in two zones of the largest (∼220 km2) hypersaline coastal lagoon in South America were addressed quarterly along 2011, and the patterns were compared among seasons and to a previous study performed during typical hypersaline conditions (i.e. 1993) to assess the short- and long-term effects of desalinisation. Our results confirmed that in 2011, Araruama Lagoon experienced a strong decrease in salinity, particularly in the autumn, with the ranging values (i.e. 37–48) remaining below to the salinities (i.e. 52–67) reported for most of the 1965–2005 period, but matching those (i.e. ≤ 41 on the average) recorded during the atypical less-hypersaline conditions of 1989–1990. Fish trophic structure recorded during 2011 was composed of five guilds, in decreasing order of biomass: planktivores (31.14%), detritivores (26.24%), invertivores (25.65%), piscivores (15.09%), and omnivores (1.58%). This structure resembled more those of similar, but comparatively less hypersaline systems in Africa and Australia, than that of extreme hypersaline lagoons in Mexico or Araruama lagoon in a typically hypersaline year. Our findings indicate that increased contributions of planktivores and detritivores could be used as promising predictors of, respectively, salination and desalinisation processes and thus shifts in the ecosystem trophic state. Variations on the biomasses of piscivores and invertivores were apparently more related to short-term salinity changes among seasons and across the lagoon zones. Since the relationships between fish trophic structure and desalinisation and its associated effects were complex, long-term studies using complementary and integrative approaches, such as stable isotopes and functional traits, are recommended to confirm our findings for Araruama Lagoon and validate our hypothesis for other similar hypersaline ecosystems.

This study addressed whether species composition and structure, and functional guilds of the fish assemblages associated with rocky substrates changed gradually with the marine-estuarine gradient in Guanabara Bay, following thus the predictions for the ecocline gradient. Fish were sampled quarterly with bottom gillnet sets between September 2010 and December 2011 in four locations of Guanabara Bay, with physical and chemical water variables being concurrently measured during fish surveys. PCA corroborated the marine-estuarine gradient between the mouth of the bay (more saline, transparent and oxygenated waters) and the innermost and more estuarine areas (high temperature, and low oxygen and salinity). Most fish metrics, especially richness, Shannon diversity, and functional guilds mirroring the degree of estuary dependence, supported the hypothesis that the ecocline concept still can be applied to explain fish distribution in this highly-eutrophic bay. The upper estuary was intensively used by young stages of the diadromous species targeted by local fisheries, but least used by marine migrants and stragglers. The sites situated near the central portion of the bay shared many species with the upper and lower estuary, probably functioning as ecological corridors for fish dispersal. Our findings supported that shifts in the composition and structure of fish assemblages in Guanabara Bay comply with the ecocline concept, urging special attention to that measures toward environmental rehabilitation and further long-term assessments should be carried out to preserve the role of this complex ecosystem as breeding, nursery, and feeding site.

The influence of water variables and the availability of complex bottom habitats in the sublittoral zone on surf-zone fish assemblages of sandy beaches in a Brazilian eutrophic bay were assessed. In total, 64 seine hauls were carried out bimonthly between October 2012 and September 2013 in two beaches located within a marine-estuarine transitional zone in Guanabara Bay and

Despite the increased use as tool for conservation of native fish, the creation of non-fishing reserves is more recent in Neotropical impoundments and its effectiveness rather variable. Although not intentionally created for conservation purposes, areas located near dams could function as fish reserves, since fishing activity is often forbidden in these sites for security reasons. We investigated the effects of a fishing-restricted area in Lajes Reservoir, a Neotropical reservoir dominated by invasive species, notably the yellow peacock bass Cichla kelberi, subject to intensive local fisheries. Cichlid populations associated with rocky banks of similar size and complexity were compared between fishing and non-fishing sites, after accounting for spatial autocorrelation. Native cichlids were significantly less abundant in the non-fishing area, in contrast to invasive cichlids. Accordingly, there were smaller individuals of the two native species in the fishing-allowed sites, where the mean size of peacock bass was also smaller. Our results suggest that angling can sometimes provide demographical control of large invasive piscivores and hence predation refuges for native fish in highly modified ecosystems such as reservoirs, thus resulting in reconciliation ecology. Fishing prohibition can sometimes be counterproductive for the conservation of native populations, illustrating the importance of context-specific management strategies.