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Fish communities of tropical lakes are commonly predicted by local environmental variables, including depth, temperature, oxygen concentration, and substrate composition. Increasingly, however, lacustrine fish communities are being impacted by invasive species. In the state of Quintana Roo, on the Caribbean versant of the Yucatan Peninsula in Mexico, inland aquaculture production has resulted in the widespread establishment of African tilapia (Oreochromis sp.). However, there are still limited quantitative data on their abundance relative to indigenous species, or their influence on native fish diversity. Here, we quantified the ichthyofauna of six lakes from this region, alongside physical and chemical environmental variables. Overall, we observed that greater dissolved oxygen concentration and shallower depths were associated with the highest fish biodiversity across lakes. Moreover, spatial comparisons additionally highlighted the importance of substrate heterogeneity and lake area as influential in determining native fish community structure. Notably, in all lakes, tilapia were relatively uncommon, comprising less than 3% of all fish captured, and their presence was not a significant predictor of indigenous fish biodiversity. Based on these results, we suggest that tilapia may have strong limitations on their population size, plausibly due to the presence of predatory native fish species, or scarce suitable ecological resources (food, breeding habitat). Conservation-focussed lake-wide management of native species via protection of core habitat characteristics may be key to promoting environmental resistance against negative effects of tilapia regional expansions. [ABSTRACT FROM AUTHOR]

Freshwater fish are in a perilous state with more than 30% of species considered critically endangered. Yet significant ecological and methodological complexities constrain our ability to determine how disturbances are impacting native fish communities. We review current methods used to assess the responses of fish communities, especially native fish, to disturbances, with a focus on lakes. These methods include contemporary population surveys, manipulative experimental approaches, paleolimnological approaches and Indigenous Knowledge and social histories. We identify knowledge gaps, such as a lack of baseline data for native fish, an inability to assess the impact of historical disturbances, stressor response dynamics in contemporary multi‐stressor environments, and natural disturbance regimes. Our assessment of the current methods highlights challenges to filling these knowledge gaps using the reviewed methods. We advocate strongly for the implementation of an integrative approach that combines emerging technologies (i.e. molecular‐based techniques in contemporary surveys and paleolimnology) and underutilised knowledge streams (i.e. Indigenous Knowledge and social histories) which should be used in concert with conventional methods. This integrative approach will allow researchers to determine the key drivers of decline and the degree of change, which will enable more informed and successful management actions. [ABSTRACT FROM AUTHOR]

Wetlands are considered as the heart of natural feeding and breeding grounds of many indigenous fishes of Bangladesh. These are also the most diversified habitat in the world. However, the wetlands of Bangladesh are in danger of extinction due to various manmade and natural causes. Therefore, wetlands need special attention to conserve this unique ecosystem of Bangladesh. As a part of the conservation measures needed for wetland ecosystem, the present study was undertaken to describe the abundance and diversity status of fish in Dingapota wetland of Bangladesh and to identify the key environmental factors influencing the fish community assemblage. A total of 52 fish species were recorded from 7 orders during the study period. Cypriniformes comprises the most abundant order (47.91%) followed by Perciformes (20.71%) and Clupeformes (20.22%). Higher number of species was recorded in post-monsoon season. Fish community assemblage was significantly differentiated among the three seasons (ANOSIM, Global R = 0.803, P < 0.05), while the overall average differences in the period of three seasons was estimated as 39.92% and similarity percentage analysis (SIMPER) revealed the greater contribution of Osteobrama cotio, Esomus danricus, Nandus nandus, Gudusia chapra and Chanda nama to ascertain this dissimilarity. Multivariate analysis based on non-metric multidimensional scaling (nMDS) generated three separate groups of each seasonal samplings and cluster analysis to find out natural grouping of samples according to their abundance. Diversity indices (Shannon-Weiner diversity (H), Margalef’s richness (D) and Pielou’s evenness (e)) were found to vary significantly among the seasons. Canonical correspondence analysis (CCA) revealed the significant roles of temperature, depth, transparency, pH, dissolved oxygen and alkalinity for structuring the community assemblage of fish in Dingapota wetland. Essential baseline information generated by this study will help the respective authority to formulate sustainable conservation measures for Dingapota wetland. [ABSTRACT FROM AUTHOR]

Indigenous Knowledge can be defined as expertise, skills, practices, ideas, experiences and information gained over a long period, sustained and passed on from generation to generation orally within a community in a particular geographic area, often forming part of its culture. The Sundarbans, the largest remaining tract of coastal mangrove wetlands in the world are surrounded by rivers, rivulets, and creeks pushing the islanders to pursue fishing as a source of subsistence. The present paper has sought to understand how the fishing community of the Sundarbans draws upon his repertoire of knowledge and beliefs to cope with the world in which it finds itself. This has required an understanding of not only the Sundarban's natural world, but its geomorphology, hydrology and also the social world--the people, economy, administration, and governance. Using the ethnographic method, this empirical study deals with the fishers' means and measures i.e. beliefs, cognitive elements, and techniques--while often preserving the traditional fabric, have evolved with time. This unique and effective indigenous knowledge needs to be conserved. Documentation of the existing valid indigenous knowledge with fishers' perception as well as scientific rationale will help in adoption and further improvement to fulfil the present need of the people. [ABSTRACT FROM AUTHOR]

Human alterations, such as hydropower development, are intensive and have negative impacts on fish and ecological environment. However, fish habitat restoration projects based on geographical morphology have not yet been reported in the Yangtze River. To explore engineering measures used to restore fish habitat structure and function, a mesoscale fish habitat restoration project was designed and constructed, which included restructuring of habitat topography in the fluctuating area. Three-dimensional computational fluid dynamics (CFD) models were used to simulate and predict the project's effect on the hydromorphology prior to construction, and an Acoustic Doppler current profiler (ADCP) was deployed to test and verify actual flow field improvement. Short-term effects on fish species sorting and their main ecological traits were examined. The results showed that vorticity and flow heterogeneity in the river reach increased, suggesting that the restoration projects created flow conditions favourable to indigenous fishes. Thus, pre-optimization using computer simulation is an essential and scientific procedure that could be used to increase the probability of river restoration success. The promotion of habitat diversity had strong effects on fish aggregation, especially for the rare and endemic fish species targeted. Fish abundance, catch biomass and species richness increased by 98.1%, 62.7% and 22.5%, respectively. There were significant differences (p < 0.05) in species number and catch abundance before and after the project. The number of rare and endemic fish species increased from four to nine species. Overall, this research provides evidence that the promotion of habitat hydraulic morphology heterogeneity accelerates the recovery of fish diversity and biomass. [ABSTRACT FROM AUTHOR]

Ichthyological investigations were performed at 11 sampling sites in the Krupinica stream basin in the period of 2020 and 2021. In total, 22 fish species of 6 families (Balitoridae, Cobitidae, Cyprinidae, Gobiidae, Lotidae, Salmonidae) were recorded in the study area. The ichthyocenosis composition varied in the longitudinal profile from source to mouth. Upper sections of the watercourses were dominated by typical rhithral species, such as Eurasian minnow (Phoxinus phoxinus), stone loach (Barbatula barbatula) and brown trout (Salmo trutta m. fario). The fish community is to some extent influeneced by human activity (stocking of indigenous fish species, water reservoir). In the middle section rheophilic fish species were in dominant position and the share of rhithral species decreased. The lower section near the mouth to Ipeľ proved to be important for the occurrence of several protected species of European importance, such as Sabanejewia bulgarica and Kessler's gudgeon (Romanogobio kesslerii). This part of the river also plays a significant role as a nursery habitat of the 0+ rheophilic species such as common nase (Chondrostoma nasus), barbel (Barbus barbus), ide (Leuciscus idus) and asp (Leuciscus aspius). [ABSTRACT FROM AUTHOR]

Western epistemologies on race defined blackness and indigeneity through scales of poverty, or more precisely, in frameworks privileging economic deprivation. Indigenous fishing communities are typically constructed as subsistence fishers whose practices only served to exacerbate resource scarcity as a result. I present a case study of the Gullah Geechee, self-defined as culturally indigenous and racially black, to explore how consciousness, indigenous knowledge, and cultural practices allow access to resources that enable them to achieve a level of autonomy. I draw on the livelihoods of three fishers, ranging from familial to commercial, to examine how the power of giving, through the cultural practices of reciprocity, sharing, and cooperation, yield abundances vital to building a sense of community. I suggest that indigenous ontologies offer alternate ways to conceptualize indigeneity in the Americas. [ABSTRACT FROM AUTHOR]

River systems globally are experiencing social-ecological changes that often impact Indigenous fishing practices, including climate change and resource developments. We explore the relationship between access to fish and well-being, and the determinants of access to fish amidst changing social-ecological conditions through interviews with 29 individuals across four Gwich'in First Nation communities in Canada's Northwest Territories. Our interviews show that socioeconomic and environmental barriers are making it harder to access fish and that this has negative implications for well-being. Despite these barriers, access to fish continues to make positive, diverse contributions to well-being in Gwich'in communities through socioeconomic factors such as sharing networks and adaptive practices that are often part of ecological monitoring and land-based education and facilitate access to fish. Increasing our understanding of the relationship between access to fish and well-being, and determinants of access to fish, can contribute to land-based programs, land-use planning, and decision-making in Gwich'in territory and other river systems. [ABSTRACT FROM AUTHOR]

Anthropogenic disturbances may cause cosmopolitan species to replace endemic species, which will alter both the within‐community diversities and between‐community similarities of stream fish assemblages. In this study, we used data collected from headwater streams within the Xin'an basin, China, to evaluate the effects of low‐head dams on the alpha diversity and community similarity of fish assemblages. Our aims were to determine whether the changes in fish diversities and similarities related to dam‐associated disturbance are dependent on the species category (i.e., indigenous vs. native‐invasive species) or data type (i.e., occurrence‐based vs. abundance‐based indices). We found that low‐head dams significantly decreased the alpha diversity of the indigenous species in the impoundments but increased that of the native‐invasive species. However, the magnitude of this change was weakened if the two categories of fishes were not distinguished. Additionally, low‐head dams significantly decreased the occurrence‐based similarities of the indigenous fishes but increased those of the native‐invasive fishes. Despite the positive correlation between the occurrence‐based and abundance‐based indices, the former significantly overestimated the community similarities. Although most pairs of communities showed the same direction of changes for the two indices, some cases presented contrasting outcomes, including "perceived homogenization" (i.e., occurrence‐based differentiation but abundance‐based homogenization) and "perceived differentiation." Our results suggest the importance of distinguishing indigenous and native‐invasive species and considering both occurrence‐based and abundance‐based indices in future research on how anthropogenic activities affect fish diversities and similarities in streams. [ABSTRACT FROM AUTHOR]

The conservation and management of inland fish and freshwater ecosystems immensely contribute to global sustainable development. The existing 'Protected Area' (PA) network does not represent freshwater resources well and seldom considers its fish communities, while designating PAs. A study was undertaken to quantitatively assess the role played by the three terrestrial PAs (IUCN category IV) in conserving fish diversity and preserving habitat quality in the river reaches bordering the three PAs of the river Pranhita. It is a unique river system in the Indian Deccan Plateau in terms of fish diversity and community structure. Field surveys were conducted during the non-monsoon and monsoon seasons in 2020–21, that recorded 53 species including endemic and threatened fishes from river Pranhita, which represent more than one-third the number of fish species of Telangana state. The higher diversity and lower dominance index value (p < 0.01) reported in PAs compared to Eco Sensitive Zones and unprotected areas during the non-monsoon season indicate the role of intact physical habitat in providing refuges to the fish species in monsoon dependent tropical rivers. The optimal water quality revealed no significant difference (p > 0.0001) between protected and unprotected river reaches, and healthy biotic integrity assessed on the basis of fish community structure was attributed to the contiguous flow and less anthropogenic disturbance. This study supports that it can be considered as a representative zone for the conservation and protection of indigenous and endemic fish species of the Godavari Basin. The results concluded that the scope of the terrestrial PA network in India could be potentially extended to their bordering aquatic ecosystems, especially rivers to maintain pristine habitat conditions and conserve the fish genetic resources to ensure the flow of ecosystem services. [ABSTRACT FROM AUTHOR]

The design and implementation of appropriate management actions to tackle the spread and negative impacts of non-indigenous fish species (NIFS) in freshwater ecosystems still remains a complex task. In an effort to address the limitations of current managerial approaches, our study develops and applies a classification framework to define non-indigenous fish assemblage types (FATs) in Mediterranean riverine ecosystems and identifies the linkage with various regional, local, biotic and abiotic environmental factors. This framework contributes to a pre-invasion stage screening and to the design of effective type-specific post-invasion management actions dealing with specific NIFS assemblages. A network analysis was applied in order to extract NIFS community level information from 393 samples obtained from 51 river basins of Greece, while a multivariate ordination analysis was conducted to detect the factors best explaining the structure and distribution of FATs. The association patterns of the study's inputs and outcomes are illustrated through an alluvial diagram, providing insights across different spatial scales. In total, five FATs were generated where the major NIFS contributors of average similarity within each modularity class revealed the key indicator species (Gambusia-FAT; Carassius/Lepomis-FAT; Pseudorasbora-FAT; Salmonids-FAT and Carp-FAT). Overall, the identified FATs varied spatially, indicating different community structure, mainly based on the diverse habitat preferences and life-history traits of indicator species. Alien FATs were mainly distributed within large and transboundary rivers, while Translocated and Salmonids FATs mostly occupied ecoregions with relatively depauperate faunas and often in biodiversity hotspots. The results of this study can identify conservation priorities within FATs, inform specific-type post-invasion management actions tackling NIFS, while in addition may provide valuable information for protecting high-priority water bodies before invasion. • A network analysis approach classified non-indigenous riverine fish assemblages. • Five non-indigenous fish assemblage types and six indicator species were generated. • Fish community-level information and distributional patterns were extracted. • Assemblages were shaped by diverse habitat preferences and indicator species' traits. • Post-invasion management insights across different spatial scales are provided. [ABSTRACT FROM AUTHOR]