Fish Richness Research Articles

Drivers of species richness and beta diversity of fishes in an Afrotropical intermittent river system.

Tropical freshwater ecosystems are some of the most threatened systems yet remain understudied relative to temperate systems. Here, we look at the drivers of community structure of fishes in a tropical and intermittent system in central Kenya. We conducted monthly sampleswithin the upper Northern Ewaso Ng'iro to assess variation in community composition and abiotic characteristics. We analyzed species richness along the longitudinal gradient, computed beta diversity within the system, relative contributions of each site, and partitioned beta diversity metrics into nestedness and turnover components. We found that, similar to temperate intermittent systems, species richness varied along the longitudinal gradient, nestedness contributions to beta diversity exceeded those of turnover, and environmental and spatial variables determined patterns of beta diversity. Sites at the highest and lowest ends of the species richness gradient showed the highest contributions to beta diversity, suggesting sites important for preservation or restoration initiatives, respectively. With ongoing water extraction and conflict over resources throughout the region, this study highlights the need for further investigations of the effects of multiple stressors on biodiversity patterns and ecosystem functioning in tropical stream communities.

Spatial patterns of site and species contributions to β diversity in riverine fish assemblages

Understanding the patterns and ecological determinants of β diversity in freshwater ecosystems is fundamental to biogeography, conservation biology, and environmental management. It has been proposed that β diversity can be divided into contributions of individual sites (LCBD) or species (SCBD) to total β diversity. However, the patterns and underlying mechanisms of LCBD and SCBD remain understudied in freshwater fish. Here, using fish assemblages sampled from the Chishui River basin, we analysed β diversity based on both abundance and presence-absence data. We also examined the relationships between LCBD and SCBD with site (i.e., community abundance, species richness, functional diversity indices, environmental factors, and spatial variables) and species (i.e., occupancy, total abundance, niche position and breadth, and functional traits) characteristics, respectively. Our results revealed that fish LCBD in the Chishui River basin was well explained by both environmental and spatial factors. Fish LCBD was negatively related to species richness and community abundance, showing that sites with high ecological uniqueness generally supported low fish richness and abundance. Furthermore, functional features of fish assemblages were also significantly associated with LCBD, with high LCBD associated with high functional specialization, originality, and uniqueness, but low functional richness, divergence, and dispersion. Abundance-based SCBD showed positive relationships with both occupancy and total abundance, whereas there were hump-shaped relationships between presence-absence SCBD and occupancy and total abundance. Niche position was negatively correlated with SCBD, whereas niche breadth and functional traits were not significant correlates of SCBD. Overall, this study suggests that understanding contributions of sites and species to β diversity is key to understanding biodiversity variation and its applied repercussions. Our results advocate the importance of environmental conditions and between-site connectivity for effective conservation of riverine fish diversity. Moreover, a simultaneous application of LCBD, species richness, SCBD, and rare species would be the most suitable approach for biodiversity conservation.

Longitudinal Patterns in Fish Assemblages after Long-Term Ecological Rehabilitation in the Taizi River, Northeastern China

Fish assemblages inhabiting the Taizi River basin have been severely degraded by anthropogenic disturbances, which weaken the basin’s ecological function and limited revitalization of the northeast industrial base. Long-term ecological rehabilitation has been conducted to restore the fish fauna and improve habitat conditions. To explore fish distribution patterns and key factors after this ecological rehabilitation, a comprehensive and detailed survey of fish fauna was conducted twice in 2021 at 33 sampling sites in the Taizi River. A total of 50 fish species from 13 families were collected, and the dominant species were P. lagowskii, Z. platypus, C. auratus and P. parva. Compared to results reported over the last decade, the increasing trend in fish richness and the change in the longitudinal fish organization were detected. The abundance variation for P. lagowskii, Z. platypus, C. auratus, P. parva, R. ocellatus and H. leucisculus along the upstream to downstream axis contributed most to the fish distribution pattern. Species replacement and addition might have jointly caused the longitudinal changes in the fish fauna, but species replacement was the main underlying mechanism. The canonical correspondence analysis (CCA) results show that the fish structure pattern was mainly shaped by cultivated land coverage and urban land coverage. Our study provides reference sites for future fish-based bioassessment and implications for region-specific management in the Taizi River.

Effects of habitat fragmentation on the recruitment and early post-settlement survival of coral reef fishes

The combined effects of global climate change and local anthropogenic stressors are leading to increasing loss and fragmentation of habitats. On coral reefs, habitat loss has been shown to influence the abundance and composition of associated fish assemblages, yet few studies have considered how habitat fragmentation may influence reef fish populations and assemblages. Herein, we compared survival, growth and recruitment of reef fish among experimental patches composed of six similar sized colonies of finely branching Pocillopora spp. but with different degrees of fragmentation: coral colonies were clumped (unfragmented), divided into two groups (low fragmentation), three groups (moderate fragmentation) or six groups (high fragmentation). Thirty settlement-stage Pomacentrus amboinensis were tagged, released onto each of the experimental patches, and their survival monitored daily for 11 days. Abundance and species richness of all reef fishes that subsequently recruited to the patches were also recorded, and used to analyse recruitment and community composition. There were no detectable differences among fragmentation treatments in the abundance or composition of reef fish assemblages that recruited to the patches, however, fragmentation influenced the survivorship of P. amboinensis. Highest survival of P. amboinensis was recorded on the unfragmented patches (61%.11 days−1) and highly fragmented habitat patches (54%.11 days−1) and lowest survival on low and moderate fragmentation treatments (47% and 48%.11 days−1, respectively). This suggests that there may be multiple competing processes that moderate mortality (e.g., predation) in unfragmented versus highly fragmented habitats, with moderate levels of habitat fragmentation having the greatest influence on the early post-settlement survival of corsal reef fish.

Development of an index based on fish, macroinvertebrates, phytoplankton, and physicochemical properties to assess urban aquatic ecosystems in Jinan, China

AbstractBecause of the rapid growth in urbanization over recent decades, urban aquatic ecosystems have been subjected to unprecedented threats and challenges. In this study, we visited 48 sites, of which 14 were reservoir sites, in water bodies in Jinan, China, on six occasions in May, August, and October of 2014 and 2015. We sampled fish, macroinvertebrates, and phytoplankton assemblages and physicochemical factors at each site. We used the richness and diversity of fish, macroinvertebrates, and phytoplankton to evaluate the condition of the aquatic ecosystems of the river sites. We also evaluated the water quality of the reservoir sites using the physicochemical factors of the State Environmental Protection Administration of China. We classified the results into five levels—excellent, good, moderate, poor, and bad—with the comprehensive evaluation index (CEI). More than 40% of the sampling sites were in either poor or bad condition. Nearly half of the excellent or good sites were in the south of Jinan. The CEI was significantly different between the reference and impaired sites; it was significantly and positively correlated with the qualitative habitat evaluation index and was significantly and negatively correlated with conductivity, total alkalinity, and ammonia nitrogen.

Benchmarking eleven biodiversity indicators based on environmental DNA surveys: More diverse functional traits and evolutionary lineages inside marine reserves

Abstract To mitigate the ongoing threats to coastal ecosystems, and the biodiversity erosion they are causing, marine‐protected areas (MPAs) have emerged as powerful and widespread conservation tools. Strictly no‐take MPAs, also called marine reserves, undeniably promote fish biomass and density, but it remains unclear how biodiversity responds to protection. Identifying which facets of biodiversity respond to protection is critical for the management of MPAs and the development of relevant conservation strategies towards the achievement of biodiversity targets. We collected 99 environmental DNA (eDNA) samples inside and outside nine marine reserves in the Mediterranean Sea to assess the effect of protection on 11 biodiversity indicators based on fish traits, phylogeny and vulnerability to fishing. We controlled for the effect of environmental heterogeneity (habitat, bathymetry, productivity, temperature and accessibility) using a principal component analysis, and for spatial autocorrelation due to potential unmeasured factors. We found a positive and significant effect of protection on only 3 out of 11 indicators: functional and phylogenic diversity but also the ratio between demerso‐pelagic and benthic species richness. Rather, total fish richness responded significantly and negatively to protection. We did not detect any significant effect of protection on threatened and elasmobranch species richness, probably due to their large home range compared to the size of Mediterranean marine reserves. Synthesis and applications: Our findings highlight the importance of looking beyond the mere number of species to fully depict and understand the effect of marine reserves on biodiversity and evaluate the effectiveness of conservation measures. Rather, we propose a dashboard of three eDNA‐based indicators that can provide an early signal of ecosystem deterioration or recovery. eDNA metabarcoding offers a powerful tool to supply site‐specific and standardized taxonomic‐, phylogenetic‐ and trait‐based biodiversity assessments, in complement to other classical techniques, such as visual censuses or video surveys, able to estimate species abundance but also individual life‐stage and size.

Patterns of species richness, abundance and individual-size distributions in native stream-fish assemblages invaded by exotic and translocated fishes.

Predicting the impacts of species introductions long has attracted the attention of ecologists yet there still is limited insight into how impacts on native assemblages vary with the degree of shared evolutionary context. Here, we used data from 535 stream-fish surveys from 15 catchments in north-eastern Spain (99,700 km2) to explore whether the relative effects on native fishes differ between fish introductions from two different ecoregions (i.e., evolutionary contexts), namely, catchments within Iberian Peninsula (i.e., 'translocated species') and catchments beyond Iberian Peninsula (i.e., 'exotic fishes'). We used hierarchical Bayesian models to relate taxon richness, abundance, and the individual-size distributions (ISDs) of native fishes to the presence, abundance, and weighted trophic level (TL) of translocated and exotic fishes, conditional on geographic and habitat covariates. Environmental covariates dominated the percentage of explained variance (≥ 65%) for all responses. Translocated fishes accounted for more of the explained variance than did exotic fishes for ISDs and abundance, but not for native fish species richness. The presence of translocated fishes was associated with lower abundance and richness of native fishes, with individuals being smaller in the presence of translocated fishes of higher TL. The presence of exotic fishes was associated with a greater abundance and richness of native fishes, with individuals generally being larger in the presence of exotic fishes. Our study suggests that translocated fishes could be as problematic as exotic fishes when angling and water transfers among catchments to deal with climate change may increase the establishment of translocated fishes. We also discuss the difficulties of using fish body size as species-blind, transferable assemblage-level trait in fish monitoring.

An ecological assessment of Australia's first community oyster gardens

SummaryOyster gardening is a community‐driven activity where oysters are grown in cages hanging off docks or other coastal infrastructure. Besides the provision of adult oysters for restoration programmes, oyster gardening may also support other ecosystem services such as providing habitat for fishes and invertebrates as well as encouraging community involvement and citizen science. Australia's first oyster gardening programme was undertaken in a canal estate on Bribie Island in Moreton Bay, Queensland between October 2016 and November 2017. Oyster gardens consisting of plastic mesh cages were deployed with either three species of bivalves (polyculture), or exclusively Sydney Rock Oysters (monoculture) to investigate whether the habitat value differed between the two garden types. After one year of growth, polyculture cages supported higher abundances and species richness of both invertebrates and fish compared to the monoculture gardens. Our study showed that oyster gardening can provide habitat for a range of invertebrate and fish species in the highly modified coastal environment of a canal estate. Further studies are needed to discern whether these oyster gardens would also support larger and mobile fauna, such as species with commercial and recreational importance.

Icthyofaunal Diversity of Kavvayi Backwaters, Malabar Coast of India: A Preliminary Study

Fish faunal diversity studies are of great importance for the effective utilization of valuable natural resources and to plan different conservation strategies. Studies on the diversity and richness of fish in Kavvayi backwaters are very rare. Hence, this study is aimed at exploring the fish resources, diversity and species richness of the fish fauna of Kavvayi backwaters of the Kerala coast, which has received very little attention hitherto. Monthly sample collections were made from four stations regularly for a period of one year, and the collection was done by netting with cast net and gill net. A total of 65 species under 51 genera, comprising 36 families belonging to 17 orders of fin fish fauna, were recorded from the Kavvayi backwater. Further studies are required to identify other fish species also and to ascertain the reasons for variations in fish faunal diversity in the Kavvayi backwater ecosystem.

Comparison of fish assemblages recorded by visual census and video census

Introduction: Underwater visual censuses are the basis of many studies on fish ecology, however, a series of limitations and errors influence the traditional visual estimation of fish richness and abundance. Video techniques have been proposed to mitigate such errors, but there are few studies that compare the effectiveness of both methods. Objective: To compare the estimates obtained through the traditional census and the video census of the fish community of two localities in the central Mexican Pacific. Methods: We studied the fish community of two bays of Huatulco, Oaxaca, Mexico. We established sampling points in each bay and applied a traditional census and a diver-operated video census. We used comparison tests and analysis of similarity tests to compare richness, abundance and diversity by locality; and permutation tests for the same parameters at each sampling point. Results: Both censuses provide similar estimates regarding the richness, abundance, and diversity by locality and by sampling points. There were no statistically significant differences between traditional census and a diver-operated video census in terms of richness, abundance, and diversity. Conclusions: Video census using the diver-operated video technique can be used as a complement or as an alternative to traditional census. Its use can provide a more complete assessment, increase data acquisition, and implement long-term monitoring programs in areas where there are economic limitations for its operation.

Diversity and distribution of fish in the Qilian Mountain Basin.

The Qilian Mountain Basin, on the north-eastern edge of the Qinghai-Tibet Plateau (QTP), supports a high diversity of native and endemic fish. However, the detailed species inventory and distribution patterns concerning fish in the whole Basin remain unknown, which hinders the conservation of biodiversity and assessment of ecological health. We compiled a comprehensive species richness and distribution database of freshwater fish in the Qilian Mountain Basin, based on field investigations and exhaustive data collection from 50 rivers or lakes. Then, we elucidated a distribution pattern using clustering and ordination analyses based on a βdissim matrix with species presence/absence data. A total of 79 freshwater fish species within eight orders, 17 families and 42 genera were recorded. The Qilian Mountain Basin could be grouped into six systems, which match the six Basins (i.e. Heihe River Basin, HHR; Qaidam Basin, QDM; Qinghai Lake Basin, QHL; Shule River Basin, SLR; Shiyang River Basin, SYR; Yellow River Basin, YR), based on the fish distribution pattern. Additionally, the spatial pattern of species distribution showed the distance decay of taxonomic similarity. Our results demonstrate that riverine connectivity resulting from historical processes plays a vital role in shaping the freshwater ichthyofauna of High Central Asia. These findings will be valuable for future systematic conservation of fish in the Qilian Mountain Basin.

The dynamism fish‐plant association: Ontogenetic variations in assemblage attributes in neotropical floodplain lakes

AbstractStructural habitat complexity provided by macrophytes is expected to increase richness and abundance of fish species. However, this topic is rarely investigated simultaneously at different periods of fish development. We sampled fish within macrophyte stands and in non‐vegetated areas at floodplain lakes and tested the hypothesis that the presence of macrophytes increases abundance and species richness of fish, in addition to changes in species composition, at different periods of fish development. Our findings demonstrated that, in different period of fish development, the highest values of fish species richness and abundance were found at sites colonised by macrophytes. Similarly, changes in fish species composition were observed between habitats colonised by macrophytes and non‐vegetated areas. Therefore, the results demonstrate that macrophyte presence plays an important role in regulating fish community structure at different periods of fish development.

Shedding light on the decline of Iberian freshwater fish species over the period 1980–2020

Abstract Freshwater fish biodiversity is experiencing an alarming decline worldwide. Understanding the main factors behind its deterioration is a key step for ecosystem restoration. In this work, large‐scale and long‐term data were used to identify the causes of the decline of native species richness in Castilla‐La Mancha. This region in central Spain covers part of six river basins belonging to four of the 11 biogeographical provinces for freshwater fish in the Iberian Peninsula. Firstly, we built a dataset that associates the presence of several fish species and a wide range of environmental variables (e.g. hydrological and hydromorphological indicators, land use classes, presence of alien fish species) at selected river sites for two different time periods (1980–2000 and 2001–2020). Secondly, we conducted an exploratory data analysis to identify possible temporal trends in the dataset. Finally, we applied the random forest algorithm to predict the response of different ecological guild‐based metrics of fish richness to the selected variables. The exploratory data analysis revealed a decrease in native fish species richness in 74% of the area studied. There was no sustained temporal trend for stressor variables, except for the number of alien species, which increased in most river sites (63%). The models of the richness of native rheophilic, native intolerant, alien rheophilic, and alien limnophilic species performed satisfactorily. Magnitude of maximum discharge, presence of alien species, land use in the catchment area and altitude were the most important predictors of richness of native intolerant and rheophilic species. Alien limnophilic species proved to be sensitive to variables related to flow regime alteration, such as the presence of dams and the number of river flow reversals, while a less degraded habitat was found to be favourable to alien rheophilic species. The results suggest that the cumulative effect of persistent altered flow regimes and water pollution, coupled with a strong increase in the number of alien species, have led to the decline of native species in the area studied. The restoration of near‐natural magnitudes of high flows when implementing environmental flows emerged as a key measure to restore ecosystem integrity. Starting from a long‐term and large‐scale dataset, this study provides new, quantitative insights into stressor–ecosystem relationships in rivers and could inform future environmental policy initiatives because it has identified the main factors leading to native fish decline and alien fish proliferation. Our findings emphasise the importance of considering metrics based on fish assemblage composition and ecological functional groups in order to disentangle the effects of stressors on fish communities.

A mesoscale analysis of relations between fish species richness and environmental and anthropogenic pressures in the Mediterranean Sea

Although there is a great knowledge about individual anthropogenic threats to different fish species in the Mediterranean Sea, little is known about how these threats accumulate and interact to affect fish species richness in conjunction with environmental dynamics. This study assesses the role of these threats in the fish richness component and identifies the main areas where the interaction between fish species richness and threats is highest. Our results show that fish richness seems to be higher in saltier and colder areas where the chlorophyll-a and phosphate concentrations are lower. Among the anthropogenic threats analyzed, the costal impact and the fishing effort seems to be the more relevant ones. Overall areas with high fish richness are mainly located along the western and northern shores, with lower values in the south-eastern regions. Areas of potential high cumulative threats are widespread in both the western and eastern basins, with fewer areas located in the south-eastern region. By describing the spatial patterns of the fish richness and which drivers explain these patterns we can also identify which anthropogenic activities can be managed more effectively to maintain and restore marine fish biodiversity in the basin.

Multifaceted fish diversities respond differently to impounding age and longitudinal location along a reservoir cascade

Damming usually modifies riverine habitats, which affects various aspects of fish diversity, especially in a reservoir cascade. Their influence on fish assemblage has been studied widely, but a lack of data from the diversity perspective remains. The Gezhouba Reservoir and Three Gorges Reservoir are two of the largest cascaded reservoirs located on the upper Yangtze River. In this study, we investigated the current fish assemblages in 2020∼2021 and retrieved 22 previous investigations in different sections of this cascade system to analyze how fish taxonomic, functional, and phylogenetic alpha- and beta-diversity change with the distance from the dams and the impounding age during 1998∼2021, and all sampling sites are located in the upper section of the dams. The total species richness and phylogenetic diversity increased significantly with the distance from the dams, but the functional diversity did not change substantially. No significant difference was found in the influence of impounding age on the three aspects of fish diversity. We observed a noticeable increase in non-indigenous fish species richness, functional diversity, and phylogenetic diversity over time, these effects were similar in areas at different distances from the dams. The species richness and phylogenetic diversity of lotic fish decreased from the lotic to lentic zones, whereas the functional and phylogenetic diversities decreased significantly with impounding age. The taxonomic beta-diversity was remarkably higher than the functional and phylogenetic beta-diversities. The differences among the three facets of beta-diversity were driven by a lower functional turnover than the taxonomic and phylogenetic turnovers, and their nestedness components were low without exception. The present study suggests that trade-offs should be considered when designing policies to protect fish diversity based on different objectives.

Desalination Discharge Influences the Composition of Reef Invertebrate and Fish Assemblages

Large-scale desalination is used increasingly to address growing freshwater demands and climate uncertainty. Discharge of hypersaline brine from desalination operations has the potential to impact marine ecosystems. Here, we used a 7-year Multiple-Before-After-Control-Impact experiment to test the hypothesis that hypersaline discharge from reverse osmosis desalination alters temperate reef communities. Using replicated, video-based, timed searches at eight sites, we sampled fish and invertebrate assemblages before, during, and after the discharge of hypersaline brine. We found that the composition of fish assemblages was significantly altered out to 55 m while the composition of invertebrate assemblages was altered out to 125 m from the outlet during hypersaline discharge. Fish richness and functional diversity increased around the outlet, while the invertebrate assemblages were no less diverse than those on reference reefs. Differences in faunal assemblages between outlet and reference sites during discharging included changes in the frequency of occurrence of both common and rare reef biota. Overall, we found the influence of hypersaline discharge on temperate reef biota to be spatially localized, with the reefs around the outlet continuing to support rich and diverse faunal communities. In some cases, therefore, the marine environmental consequences of large-scale, well-designed, desalination operations may be appropriately balanced against the positive benefits of improved water security.

Sea‐surface temperature anomalies mediate changes in fish richness and abundance in Atlantic and Gulf of Mexico estuaries

AbstractAimAnthropogenic warming of marine systems has caused biological and physiological responses that are fundamentally altering ecosystem structure. Because estuaries exist at the land‐ocean interface, they are particularly vulnerable to the effects of ocean warming as they can undergo rapid biogeochemical and hydrological shifts due to climate and land‐use change. We explored how multiple components of estuarine fish diversity—turnover, richness, and abundance—have changed in the North Atlantic and Gulf of Mexico estuaries across space and time and the drivers of change.LocationNorth Atlantic and Gulf of Mexico.TaxaFish.MethodWe compiled long‐term (>30 years), continent‐wide fisheries independent trawl surveys conducted in estuaries—from the Gulf of Maine to the Gulf of Mexico (U.S. waters)—and combined these with climate and land‐use‐land‐cover data to examine trends and ecological drivers of fish richness, abundance and turnover using mixed‐effect models.ResultsSpecies richness, abundance and turnover have increased in North Atlantic and Gulf of Mexico estuaries in the last 30 years. These changes were mediated largely by sea‐surface temperature anomalies, especially in more northern estuaries where warming has been relatively pronounced.Main ConclusionThe increasing trajectory of turnover in many estuaries suggests that fish communities have changed fundamentally from the baselines. A fundamental change in community composition can lead to an irreversible trophic imbalance or alternative stable states among other outcomes. Thus, predicting how shifting community structures might influence food webs, ecosystem stability, and human resource use remain a pertinent task.

EDNA metabarcoding as a promising conservation tool to monitor fish diversity in Beijing water systems compared with ground cages

Fish diversity, an important indicator of the health of aquatic ecosystems, is declining sharply due to water pollution, overfishing, climate change, and species invasion. For protecting fish diversity, effective surveying and monitoring are prerequisites. In this study, eDNA (environmental DNA) metabarcoding and ground cages were used to survey the fish diversity of the Chaobai and Beiyun Rivers in Beijing. Based on the two methods, we identified 40 species, belonging to 35 genera, 18 families, and six orders. The richness of fish identified by eDNA metabarcoding was significantly higher than that captured by ground cages in both rivers. The fish captured by the ground cage method were all recognized by eDNA metabarcoding, except Squalidus wolterstorffi and Saurogobio dabryi, which were captured only in ground cages. The correlation of relative abundance between the two methods was affected by the properties of the rivers, such as the flow rate. Fish caught by ground cage in the Beiyun River were identified by eDNA, but not in the Chaobai River. Our results also suggest that the Chaobai River has higher fish diversity than the Beiyun River and different community assemblage. In addition to differences in the natural properties of the focal rivers, the development of urbanization is also an important contributor to different community structures overserved. eDNA metabarcoding as a new survey tool has great application prospects, it provides certain theoretical data and methodological references for the protection and management of river fish diversity.

Freshwater fish biodiversity restoration in floodplain rivers requires connectivity and habitat heterogeneity at multiple spatial scales

With a sixth mass extinction looming and freshwater biodiversity declining at unprecedented rates, evaluating ecological efficacy of river restoration efforts is critical in combatting global biodiversity loss. Here, we present a comprehensive study of the functioning for fishes of 46 river restoration projects in the river Rhine, one of the world's most heavily engineered lowland rivers. Floodplains with permanent, either one- or two-sided lateral connectivity to the main channel, favour total fish abundance, and are essential as nursery areas for riverine fishes. Habitat heterogeneity had a strong positive effect on species richness but was negatively related with fish abundances. However, the effects of environmental variables varied between ecological groups and spatial scales. Surprisingly, richness of critical rheophilic fishes declined with large-scale habitat heterogeneity (~1000 m), while it increased at small scales (~100 m), possibly because of the presence of unfavourable habitats for this ecological group at larger scales. Clearly, there is no one-size-fits-all design for river restoration projects. Whether a river section is free-flowing or impounded dictates the scope and efficacy of restoration projects and, within a river section, multiple complementary restoration projects might be key to mitigate freshwater fish biodiversity loss. An essential element for success is that these projects should retain permanent lateral connection to the main channel.

Habitat-specific fish fauna responses to different management regimes in the largest coral reef complex in the South Atlantic

While marine protected areas (MPAs) are increasing worldwide, it is still needed to assess the effectiveness of those already consolidated. Methods and ecological assessments to understanding integrated and habitat-specific management regimes are still scarce and insufficient for policy implications and biodiversity conservation. Through Baited Remote Underwater Video (BRUV), we used fish assemblages as proxy of ecological and managerial status in two reef habitat types along three protection levels at Abrolhos Bank - the largest and most biodiverse coral reef complex of the South Atlantic. We found completely distinct responses in the fish fauna between the top (shallow) and bottom (deep) habitats of the unique “chapeirões” pinnacle reef formations. In the most protected zone (no-take), higher richness and abundance of commercial fish and more diverse trophic structure was observed. Particularly, large (sharks and groupers) and small carnivores (snappers) were more abundant and distributed more homogeneously over both reef habitats in the strictly enforced no-take zone. Abundance of these top-predators decreased from the low enforcement no-take zone to the multiple use area, where they were often absent while their typical preys (primary and secondary consumers) were thriving, notably in the top habitats. These outcomes highlight the importance to focus investigations not selectively on a single habitat type or depth zone in order to properly assess MPA effectiveness. Consequently, the monitoring and protection of fish species supported by marine spatial planning may benefit from an improved understanding of ecological functioning provided by MPA performance.