Species boundaries of the whiptail catfish Rineloricaria (Siluriformes: Loricariidae) from the Paraíba do Sul River drainage, southeastern Brazil, with species redescriptions and description of a new species.

Species of the catfish genus Rineloricaria are common in the Paraíba do Sul River basin, in southeastern Brazil; here we present a revision of the taxonomic diversity and geographic distribution of the species of the genus inhabiting the basin, based on novel morphologic and molecular data. Five species delimitation methods based on cytochrome C oxidase subunit 1 nucleotide sequences yielded comparable molecular operational taxonomic units. The automatic barcode gap discovery, assemble species by automatic partitioning, barcode index number, and Bayesian implementation of the Poisson tree process methods supported the recognition of five evolutionary lineages. These taxonomic units were assigned to the previously described Rineloricaria nigricauda, Rineloricaria steindachneri, Rineloricaria zawadzkii, and Rineloricaria nudipectoris, and an additional undescribed species. R. zawadzkii was further divided into two intraspecific geographically structured lineages using the generalized mixed Yule coalescent delimitation method. A maximum likelihood phylogenetic analysis revealed that the five lineages from the Paraíba do Sul have closer relationships to different species from southern and southeastern Brazil (Ribeira de Iguape, Lagoa dos Patos, Uruguay, Paraguay, and Parana river basins) than to each other. Based on the analysis of lectotypes, recently collected material, and specimens from ichthyological collections, the poorly described R. nigricauda and R. steindachneri are redescribed following current descriptive standards. The undescribed species from the middle and upper Paraíba do Sul River basin is formally described. The description of a new species, along with the description of species boundaries in R. nigricauda and R. steindachneri, contributes to the knowledge of the ichthyofauna of the Paraíba do Sul River basin and adjacent coastal drainages of southeastern Brazil. An identification key for the species of Rineloricaria occurring in the Paraíba do Sul River basin is provided.

Stochastic process is main factor to affect plateau river fish community assembly.

Plateau river ecosystems are often highly vulnerable and responsive to environmental change. The driving mechanism of fish diversity and community assembly in plateau rivers under changing environments presents a significant complexity to the interdisciplinary study of ecology and environment. This study integrated molecular biological techniques and mathematical models to identify the mechanisms influencing spatial heterogeneity of freshwater fish diversity and driving fish community assembly in plateau rivers. By utilizing environmental-DNA metabarcoding and the null model, this study revealed the impact of the stochastic process on fish diversity variations and community assembly in the Huangshui Plateau River of the Yellow River Basin (YRB) in China. This research identified 30 operational taxonomic units (OTUs), which correspond to 20 different fish species. The findings of this study revealed that the fish α-diversity in the upstream region of Xining is significantly higher than in the middle-lower reach (Shannon index: P = 0.017 and Simpson: P = 0.035). This pattern was not found to be related to any other environmental factors besides altitude (P = 0.023) that we measured. Further, the study indicated that the assembly of fish communities in the Huangshui River primarily depends on stochastic ecological processes. These findings suggested that elevation was not the primary factor impacting the biodiversity patterns of fish in plateau rivers. In plateau rivers, spatial heterogeneity of fish community on elevation is mainly determined by stochastic processes under habitat fragmentation, rather than any other physicochemical environmental factors. The limitations of connectivity in the downstream channel of the river could be taken the mainly responsibility for stochastic processes of fish community in Huangshui River. Incorporating ecological processes in the eDNA approach holds great potential for future monitoring and evaluation of fish biodiversity and community assembly in plateau rivers.

eDNA reveals spatial homogenization of fish diversity in a mountain river affected by a reservoir cascade.

One of the main reasons for the decline in global freshwater biodiversity can be attributed to alterations in hydrological conditions resulting from dam construction. However, the majority of current research has focused on single or limited numbers of dams. Here, we carried out a seasonal fish survey, using environmental DNA (eDNA) method, on the Wujiang River mainstream (Tributaries of the Yangtze River, China) to investigate the impact of large-scale cascade hydropower development on changes in fish diversity patterns. eDNA survey revealed that native fish species have decreased in contrast to alien fish. There was also a shift in fish community structure, with declines of the dominant rheophilic fish species, an increase of the small-size fish species, and homogenization of species composition across reservoirs. Additionally, environmental factors, such as temperature, dissolved oxygen and reservoir age, had a significant effect on fish community diversity. This study provides basic information for the evaluation of the impact of cascade developments on fish diversity patterns.

The concept of "state fishes of India": Current status, knowledge gaps, and strategic plans for conservation and sustainable utilization.

The concept of "state fishes of India" highlights the importance and significance of the prioritized fish species distributed across various states within the country. This review article systematically documents the current status of state fishes from various perspectives, identifies the prevailing knowledge gaps, and also highlights the issues and strategic plans essential for the conservation and sustainable utilization of these valuable genetic resources. A total of 8357 publications were checked for the consolidated information on state fish species, and the appropriate items were selected under eight categories: biology, physiology and nutrition, aquaculture, habitat and environmental parameters, genetics and biotechnology, harvest and postharvest, fish health management, and others. The synthesized information was used to present the current status of research and development on state fish species. The knowledge gaps that are to be addressed are also depicted under the perspectives of fisheries management and conservation aquaculture. Based on the findings, strategic plans for the targeted conservation programmes are proposed and discussed under various in situ and ex situ conservation measures. Further, the departmental processes involved in the declaration, the importance of stakeholder involvement, namely, local communities and policymakers, in fostering effective conservation measures, and planning for utilization of these valuable fish genetic resources are also indicated.

Fish community structure and functional guild composition in an anthropogenically impacted, temporarily closed sandbar estuary.

This study investigates the fish assemblage in a temporarily-closed sandbar estuary along India's west coast, across different zones and seasons. Moderate species diversity (54 species), low species abundance, varying fish diversity from lower to upper estuarine gradient (higher counts in lower zones, and decreasing from middle to upper zones), and higher prevalence of marine migrants (estuarine use) and piscivorous species (feeding mode) were the significant characteristics of the estuary. Distinct spatial, seasonal, and estuarine mouth state-based variations were recorded in the estuary, based on diversity indices and count of taxa. Peak diversity and abundance were noted during the pre-monsoon, and during the open mouth state of the estuary. The entire estuarine gradient is anthropogenically impacted by a multitude of stressors, except at the estuarine mouth region, which is favored by marine connectivity. The fish assemblage structure in Poonthura estuary (PE) has thus far remained unaffected by anthropogenic disturbances. Nevertheless, growth and nursery function of the estuary have been significantly compromised. The predominance of juvenile fish in the ecosystem, and prevailing anthropogenic stressors from point and non-point sources underscore the necessity for long-term maintenance of the population of coastal species, as well as a need for developing and implementing urgent management strategies for this fragile ecosystem.

A new distinctively striped species of bushynose catfish (Siluriformes: Loricariidae: Ancistrus) from the Pachitea River drainage, Pasco, Peru.

With 76 currently valid species, the bushynose catfish genus Ancistrus is the fourth most species-rich catfish genus, yet Ancistrus diversity remains underestimated, with many species still undescribed. This is especially true of the Peruvian Andean headwaters of the Amazon, which are rich in unnamed Ancistrus species but have received little recent taxonomic attention. We describe a distinctively striped new Ancistrus species from tributaries of the Palcazú River, in the Pachitea-Ucayali-Amazonas drainage basin. The new species differs from all congeners by having black, vermiculated lines covering the head and two to four distinct black, parallel, lateral body stripes from head to caudal fin (vs. body uniformly colored or with dark or light spots or blotches over head and body, or black vermiculate lines on flanks). The new species is the fifth valid species of Ancistrus described from the rich Ucayali River ichthyofauna. It has previously been recognized in the aquarium fish trade as L267.

Historical changes in fish landings indicate a significant shift in fish catch composition and biodiversity loss in the Nile-Delta lakes.

To monitor the changes in fish biodiversity and to elucidate the factors responsible for these changes, the landings composition (LC) over the past 30 years in the Nile-Delta lakes was quantitatively analyzed. The LC data indicates a shift in target species towards demersal opportunistic species. A significant difference (P < 0.001) between two main intervals highlighted in both PERMANOVA and PCA plot; the first interval (1991-2002) is dominated by Tilapia and rare species, while the second interval (2003-2020) is dominated by the opportunistic catfish and mullet species. Noticeable declines in species richness and landings of rare species were observed, where rare taxa either have been overexploited or they may be positively affected by increasing pollution levels than do other dominated species such as Tilapia. In contrast, opportunistic fish species such as catfish and mullet, have flourished in such polluted water due to their ability to tolerate seasonal pollution-related hypoxia.

eDNA metabarcoding reveals differences in fish diversity and community structure in heterogeneous habitat areas shaped by cascade hydropower.

Freshwater ecosystems are under great threat from humans, among which habitat heterogeneity is the most obvious, being one of the important reasons for the decline of fish diversity. This phenomenon is particularly prominent in the Wujiang River, where the continuous rapids of the mainstream have been divided into 12 mutually isolated sections by 11 cascade hydropower reservoirs. Based on the fact that conventional survey methods are more harmful to the ecological environment, the efficient and noninvasive environmental DNA metabarcoding (eDNA) approach was used in this study to conduct an aquatic ecological survey of the 12 river sections of the mainstream of the Wujiang River. A total of 2299 operational taxonomic units (OTUs) were obtained, corresponding to 97 species, including four nationally protected fish species and 12 alien species. The results indicate that the fish community structure of the Wujiang River mainstream, which was originally dominated by rheophilic fish species, has been changed. And there are differences in fish species diversity and species composition among the reservoir areas of the mainstream of the Wujiang River. The fish species in the area have gradually declined under the influence of anthropogenic factors such as terraced hydropower and overfishing. The fish populations consequently have demonstrated a tendency to be species miniaturized, and the indigenous fish are severely threatened. In addition, the fish composition monitored by the eDNA approach was found to be close to the fish composition of historical information on the Wujiang River, indicating that eDNA approach may be used as a complementary tool to conventional methods in this basin.

Fish community structure and functional guild composition in a large tropical estuary (Vembanad Lake, India).

The fish guild structure of 96 fish species inhabiting the Vembanad Lake, an open, large, well-mixed coastal estuary along the south-west coast of India, was studied based on samples from upper (freshwater), middle (estuarine), and lower (saline) zones representing three major seasons (monsoon, post-monsoon, and pre-monsoon). Functional group assessment revealed seven ecological guilds (marine estuarine opportunists, freshwater, marine estuarine dependent, estuarine, catadromous, anadromous, and amphidromous), six feeding guilds (detritivore, zooplanktivore, herbivore, zoobenthivore, omnivore, and carnivore), three vertical distribution guilds (demersal, benthopelagic, and pelagic), five reproductive-mode functional groups (oviparous with pelagic eggs, oviparous with benthic eggs, oviparous guarders, viviparous and ovoviviparous), and five flow-preference guilds (rheophilic A1, eurytopic, rheophilic A2, rheophilic B, and rheophilic C). The estuary was characterized by high species diversity, low individual species abundance, complex guild structure, varying fish diversity from upper to lower estuary and higher proportion of marine rather than 'true' estuarine species. The absence of a significant relationship between season and fish guild structuring could be due to high resource availability in the estuary and low ecological connectivity between upper and lower estuarine zones as a result of anthropogenic interventions in the middle zone. Salinity variations considerably influenced the fish guild formation in the estuary. A drastic change in the hydrography of the estuary over the past sixty years due to topographical alterations has transformed the fish guilds resulting in a considerable increase in freshwater species and a reduction in marine and estuarine-dependant species.

Boosting freshwater fish conservation with high-resolution distribution mapping across a large territory.

The lack of high-resolution distribution maps for freshwater species across large extents fundamentally challenges biodiversity conservation worldwide. We devised a simple framework to delineate the distributions of freshwater fishes in a high-resolution drainage map based on stacked species distribution models and expert information. We applied this framework to the entire Chinese freshwater fish fauna (>1600 species) to examine high-resolution biodiversity patterns and reveal potential conflicts between freshwater biodiversity and anthropogenic disturbances. The correlations between spatial patterns of biodiversity facets (species richness, endemicity, and phylogenetic diversity) were all significant (r = 0.43-0.98, p < 0.001). Areas with high values of different biodiversity facets overlapped with anthropogenic disturbances. Existing protected areas (PAs), covering 22% of China's territory, protected 25-29% of fish habitats, 16-23% of species, and 30-31% of priority conservation areas. Moreover, 6-21% of the species were completely unprotected. These results suggest the need for extending the network of PAs to ensure the conservation of China's freshwater fishes and the goods and services they provide. Specifically, middle to low reaches of large rivers and their associated lakes from northeast to southwest China hosted the most diverse species assemblages and thus should be the target of future expansions of the network of PAs. More generally, our framework, which can be used to draw high-resolution freshwater biodiversity maps combining species occurrence data and expert knowledge on species distribution, provides an efficient way to design PAs regardless of the ecosystem, taxonomic group, or region considered.

Potenciación de la conservación de peces de agua dulce con mapeos de distribución de alta resolución a lo largo de un territorio extenso Resumen La falta de mapas de distribución en alta resolución para las especies de agua dulce en grandes extensiones es un reto importante para la conservación mundial de la biodiversidad. Diseñamos un marco simple para delinear la distribución de los peces de agua dulce en un mapa de drenaje en alta resolución basado en los modelos apilados de la distribución de las especies y la información de expertos. Aplicamos este marco a toda la ictiofauna de agua dulce en China (>1600 especies) para analizar los patrones en alta resolución de la biodiversidad y revelar los conflictos potenciales entre la biodiversidad de agua dulce y las perturbaciones antropogénicas. Todas las correlaciones entre los patrones espaciales de las facetas de la biodiversidad (riqueza de especies, endemismo y diversidad filogenética) fueron importantes (r = 0.43-0.98, p < 0.001). Las áreas con valores altos de diferentes facetas de la biodiversidad se traslaparon con las perturbaciones antropogénicas. Las áreas protegidas existentes que actualmente cubren el 22% del territorio de China, protegen 25-2% del hábitat de los peces, 16-23% de las especies y 30-31% de las áreas de conservación prioritarias. Además, 6-21% de las especies se encontraban totalmente desprotegidas. Estos resultados sugieren que se necesita extender la red de áreas protegidas para asegurar la conservación de los peces de agua dulce de China y los bienes y servicios que proporcionan. En concreto, los niveles medio a bajo de los grandes ríos y sus lagos asociados del noreste al suroeste de China albergaron los ensambles de especies más diversos y por lo tanto deberían ser el objetivo de las futuras expansiones de la red de áreas protegidas. De forma más generalizada, nuestro marco, el cual puede usarse para trazar mapas en alta resolución de la biodiversidad de agua dulce al combinar los datos de presencia de las especies y el conocimiento de los expertos sobre su distribución, proporciona un método eficiente para diseñar las áreas protegidas sin importar el ecosistema, región o grupo taxonómico considerado.

A review of fish diversity, decline drivers, and management of the Tanguar Haor ecosystem: A globally recognized Ramsar site in Bangladesh.

Tanguar Haor (TH), an ecologically critical area (ECA) and a Ramsar site of worldwide significance, is an essential wetland ecosystem for the Bangladesh's economic, ecological, social, and cultural aspects. Fish, aquatic plants, amphibians, reptiles, birds, and mammals are notable among the floral and faunal compositions found in this haor. Unfortunately, unsustainable exploitation of its natural resources poses a serious threat to the TH ecosystem. Therefore, the broad objective of this study was to review the status of fish biodiversity along with the driving factors of biodiversity loss and the management issues of the TH ecosystem. A total of 143 species of fishes (137 indigenous and 6 exotic) under 35 families, and 12 orders were documented during the last two decades. Species diversity of the haor has been changed over time due to the effects of climatic, anthropogenic, socioeconomic, and policy related drivers. Furthermore, high dependency on fisheries resources, poverty, and the lack of empowerment to manage the TH fishery were responsible for fish diversity decline. Therefore, ecosystem based co-management through active participation of local community, establishment of balanced fishing tactics, and strengthening alternative livelihoods for highly depended poor harvesters are strongly recommended for the proper management of this valued wetland ecosystem. Furthermore, this review proposes immediate and useful conservation initiatives for the studied wetlands, including comprehensive stock assessment, establishment of gene banks and fish sanctuaries, a combination of input and output control, and regulation with the ECA and RAMSAR guidelines.

Comparación de cuatro métodos para contar peces en una bahía tropical: el caso del Área Marina de Manejo Bahía Santa Elena en el Pacífico de Costa Rica / Comparison of four methods to count fish in a tropical bay: the case of the Santa Elena Bay Marine Management Area in the Pacific of Costa Rica

Resumen Introducción: La naturaleza tropical está experimentando una amenaza sin precedentes que incluye comunidades de peces costeros que requieren un constante seguimiento de la presencia de especies. El uso simultáneo de varios métodos de monitoreo debería reducir el sesgo causado por la selectividad de cada método. Objetivo: Este estudio uso cuatro diferentes métodos de muestreo a lo largo de dos años para evaluar y comparar los ensamblajes de peces en el Área Marina de Manejo Bahía Santa Elena, Pacífico de Costa Rica. Métodos: Examinamos los cambios en la riqueza y composición de especies entre épocas de afloramiento y no afloramiento entre julio de 2019 y febrero de 2020. Aplicamos censos visuales, cámaras remotas submarinas; líneas de fondo; y pesca deportiva. Resultados: Identificamos 140 especies de peces (54 familias); las cámaras submarinas remotas detectaron el 83 %, seguido por los censos visuales submarinos (65 %), la pesca deportiva (16 %) y las líneas de fondo (14 %). Solo el método de pesca deportiva detectó diferencias en la riqueza y composición de especies entre temporadas. Conclusión: Las cámaras remotas parecen ser el mejor método para el conteo de especies y la pesca deportiva para detectar diferencias estacionales en las costas tropicales similares a la aquí estudiada.

Abstract Introduction: Tropical nature is experiencing an unprecedented threat that includes coastal fish communities that requires a close monitoring of species presence. The simultaneous use of several monitoring methods should reduce the bias caused by the selectivity of each method. Objective: This study used four different sampling methods over two years to assess and compare fish assemblages in the Santa Elena Bay Marine Management Area (AMM-BSE), North Pacific of Costa Rica. Methods: We examined changes in species richness and composition between upwelling and non-upwelling seasons from July 2019 and February 2020. We applied visual censuses, underwater remote cameras; bottom lines; and sport fishing. Results: We identified 140 species of fish (54 families); remote underwater cameras detected 83 %, followed by underwater visual censuses (65 %), sport-fishing (16 %) and bottom lines (14 %). Only the sport-fishing method detected differences in species richness and composition between seasons. Conclusion: Remote cameras appear to be the best method for species counts, and sport-fishing to detect seasonal differences in tropical coasts similar to the one studied here.

Use of geographical information systems (GIS) in assessing ecological profile, fish community structure and production of a large reservoir of Himachal Pradesh.

The present study demonstrates the spatial analysis and mapping of fish and different measures of environmental parameters and fish diversity of Pong reservoir, Himachal Pradesh, using Kriging spatial interpolation methods for geographical information system mapping. Seasonal data on environmental parameters, potential fish habitat and fish diversity was collected from lentic (dam), lentic (reservoir), transitional and lotic zone of the reservoir.. Important environmental parameters like water temperature, dissolved oxygen, electrical conductivity, water depth and transparency showed variations across the different zones of the reservoir. The sediment of the reservoir was sandy clay loam in nature as per texture analysis. Fish species richness, Shannon index and evenness index showed a similarity of the lotic and lentic (reservoir) zones of the reservoir. Six potential fish breeding grounds were identified in the reservoir indicating high conservation significance. The analysis of data showed a declining trend in fish production from 456.9 tonnes during the decade 1976-1987 to 347.91 tonnes during 2009-2020. The factors like anthropogenic climate change, predation of a stocked fish juvenile by water birds, undersized fish stocking and unscientific management are the probable reasons for the decreasing fish production. The spatial variation pattern of the water spread area, environmental parameters, fish catch and potential fish breeding grounds depicted in the GIS platform can be used as an important information base by the policy makers for fisheries management. The stocking of large size fish as a stocking material and adequate protection of the potential fish breeding grounds are the key advisories for the sustainable enhancement of fisheries as well as conservation.

Impacts of brush pile fishing on fish biodiversity: A case study of the Shari-Goyain River in Bangladesh.

Brush pile (katha), a fish aggregating device, has been widely used in the Shari-Goyain River since 2003 to congregate fish for easier catch. Katha is usually used during the winter season when the water depth decreases. Hence, this experiment was conducted from November 2018 to March 2019 on katha fishing to investigate its status and impacts on fisheries resources of the Shari-Goyain River in the Sylhet district of Bangladesh. The study was based on the hypothesis that katha fishing might have detrimental impacts to fish biodiversity and production. Data were obtained through a questionnaire-based survey, personal interviews, catch assessment (CA), focus group discussions, and key informant interviews. A total of 54 species were documented, including two exotic fish species (tilapia and common carp) and 3 species of prawn during harvesting of the kathas. The catch per unit effort (CPUE) (kg/gear/ha/person/hour) was the highest in December (1.13 ± 0.37), followed by November (1.06 ± 0.40), January (0.80 ± 0.25), February (0.71 ± 0.23), and March (0.52 ± 0.21). The catch per unit area (CPUA) (kg/ha) was the highest in November (264.66 ± 18.21), followed by December (205.05 ± 27.77), January (175.02 ± 76.04), February (147.73 ± 52.11), and March (102.08 ± 41.04) where significant differences (p < 0.05) among the months were observed. Average catch per katha in a month ranged from 41.09 ± 16.11 to 12.42 ± 5.89 kg, with a mean of 24.29 ± 11.08 kg, and a significant decrease in average catch was observed with the progression of months. The most species richness was noticed in December (38), followed by November (35), January (34), February (28), and March (25). Siluriformes (39.123%) was the most dominant order, followed by Cypriniformes (33.956%), Decapoda (14.661%), and Ovalentaria (3.278%). According to the CA and respondents' perception, indiscriminate harvesting of fish by katha fishing can be a cause of fish biodiversity loss as it reduces open water catches, total production, and disturbs the ecosystem. From the research findings, it is suggested that katha fishing should be stopped for sustainable management and conservation of fisheries resources in the Shari-Goyain River. Research on the effects of katha fishing should be conducted in other open waters of Bangladesh where this type of fishing is common.

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.

Environmental and anthropogenic impact on conservation and sustainability of marine fish diversity.

Marine fish biodiversity and conservation linked to human livelihoods along the coast were studied in 2019 using a survey and personal interviews to investigate the effects of environmental and anthropogenic issues on changes in marine fish diversity that affect sustainability. The Zoological Survey of India (ZSI) authenticated 42 finfish, 6 crabs, and 1 shrimp from three groups collected along the coastal zone. The estimated fish species diversity index revealed that alpha and beta biodiversity were more prevalent in the study zone than gamma fish diversity. When the collected fish species were compared to the International Union for Conservation of Nature (IUCN) threatened lists, 51% were found to be least concerned. The variation in the livelihood status, age group, religious, education, houses, training, graft, and gear of fishermen was 93.6% and 4.3%, respectively, according to the principle component analysis. The observation of 51% of the least concerned species in the study zone suggests species declination as a result of overexploitation of natural resources. The study suggests that strict conservation measures be put in place to ensure the sustainability and conservation of fish diversity.

Global change and physiological challenges for fish of the Amazon today and in the near future.

Amazonia is home to 15% (>2700, in 18 orders) of all the freshwater fish species of the world, many endemic to the region, has 65 million years of evolutionary history and accounts for 20% of all freshwater discharge to the oceans. These characteristics make Amazonia a unique region in the world. We review the geological history of the environment, its current biogeochemistry and the evolutionary forces that led to the present endemic fish species that are distributed amongst three very different water types: black waters [acidic, ion-poor, rich in dissolved organic carbon (DOC)], white waters (circumneutral, particle-rich) and clear waters (circumneutral, ion-poor, DOC-poor). The annual flood pulse is the major ecological driver for fish, providing feeding, breeding and migration opportunities, and profoundly affecting O2, CO2 and DOC regimes. Owing to climate change and other anthropogenic pressures such as deforestation, pollution and governmental mismanagement, Amazonia is now in crisis. The environment is becoming hotter and drier, and more intense and frequent flood pulses are now occurring, with greater variation between high and low water levels. Current projections are that Amazon waters of the near future will be even hotter, more acidic, darker (i.e. more DOC, more suspended particles), higher in ions, higher in CO2 and lower in O2, with many synergistic effects. We review current physiological information on Amazon fish, focusing on temperature tolerance and ionoregulatory strategies for dealing with acidic and ion-poor environments. We also discuss the influences of DOC and particles on gill function, the effects of high dissolved CO2 and low dissolved O2, with emphasis on water- versus air-breathing mechanisms, and strategies for pH compensation. We conclude that future elevations in water temperature will be the most critical factor, eliminating many species. Climate change will likely favour predominantly water-breathing species with low routine metabolic rates, low temperature sensitivity of routine metabolic rates, high anaerobic capacity, high hypoxia tolerance and high thermal tolerance.

Environmental flow in the context of dams and development with special reference to the Damodar Valley Project, India: a review.

Environmental flow is the minimum flow required in a fluvial system to maintain its ecological health and to promote socio-economic sustainability. The present work critically examines the concept of the environmental flow in the context of dams and development using a systematic methodology to find out the previous works published during the last 3 decades (1990-2020) in different search engines and websites. The study reviews that structural interventions in the form of dams, barrages, weirs, etc. impede the natural flow of the rivers. Moreover, other forms of development such as industrialization, urbanization, and expansion of modern agriculture also exacerbate the problems of environmental flow across the world, especially in monsoon Asia. The present case of the environmental flow for the Damodar River portrays that the construction of dams and barrages under the Damodar Valley Project have significantly altered the flow duration, flood frequency, and magnitude (high-frequency low magnitude events in the post-dam period), while urban-industrial growth in the basin has polluted the river water (e.g., lower dissolved oxygen and higher biological oxygen demand). This typical alteration in the flow characteristics and water quality has threatened aquatic organisms, especially fish diversity and community structure. This review will make the readers aware of the long-term result of dam-induced fluvial metamorphosis in the environment through the assessment of environmental flow, species diversity, flow fluctuation, and river pollution. The study may be useful for policy-making for ushering in the sustainable development pattern that will attract future researchers, planners, and stakeholders.

Spatio-temporal changes in ecology and fisheries in a tropical large Indian reservoir: insights from a long-term data series for sustainable development.

The geographic information systems (GIS) play an important role in all geospatial aspects of assessment, monitoring, and management of inland open water resources for strategic development in the fisheries sector. In India, reservoir fisheries development is one of the flagship programme and several initiatives have been taken up towards enhancement and sustainable development. The present study investigates spatio-temporal changes in ecology and fisheries in Hirakud reservoir, Odisha, build across river Mahanadi which features one of the largest dams in South Asia during 2016-17 to 2018-19. The reservoir is mainly utilized for electricity generation, irrigation and offers tremendous scope to support fisheries and livelihood. The mean water spread area during 2016-17 to 2018-19 was at the minimum (42721 ha) during premonsoon period and was at the maximum (62059 ha) during monsoon. Most of the water quality parameters including nitrate, BOD, and alkalinity during 2016-17 to 2018-19 were higher in the premonsoon period and overall, the parameters were under favorable range for fisheries. The present investigation from the fish landing sites of the reservoir, recorded merely 40 fish species, indicating loss of fish diversity as compared to the historical reports. The IUCN conservation status showed that among the 40 species only one species, Wallago attu is under the VU category and 4 species Chitala chitala, Ompok bimaculatus, Ailia colia, and Bagarius bagarius are under the NT category. The fish production in the reservoir was 8200 t during 2018-19. The analysis of time series annual fish catch data using the ARIMA model forecasted the increasing trend of fish production. The water quality parameters were presented in the GIS platform for a better understanding of the spatial variations over time. Habitat protection of fish breeding grounds, closed seasons, mesh size regulations, scientific management, and community participation are recommended as the measures for conservation of fish diversity and sustainable enhancement of fish production in the reservoir.

Fish distribution and behaviour with regard to the time of day and the anthropogenic structural modification of the shallow littoral.

The shallow littoral zone is under a variety of environmental drivers and anthropogenic pressures. As these factors are highly dynamic, they may affect the distribution and behaviour of littoral fish. The present study investigates the effect of the time of day and the benthic habitat type on the shallow littoral fish community. Diel variations in total fish abundance, community composition, species abundance and behaviour were studied in two neighbouring stations in the Patraikos Gulf (Greece): one with cobble seabed cover and another with anthropogenic habitat structural modifications, like large artificial blocks, rocks and other objects. Visual census revealed that community composition differed depending on both the time of day and the habitat type. Total abundance was highest in the morning, whereas both diel abundance and habitat use were found to be taxon specific, with most species showing a preference for the artificial rocky habitat. Diel differences in species behavioural patterns were also observed, with a greater percentage of fish being active during the day (morning and noon) rather than in the afternoon. Although the fish community does not change entirely within a day or between adjacent locations, it is significantly variable in even small spatial and temporal scales. Consequently, there are implications for the design and implementation of sampling designs and monitoring plans that should be consistent in time of day throughout the sampling period and include locations structurally modified by humans. Furthermore, the management of the shallow littoral zone should consider the small-scale variability and alternate anthropogenic habitat with natural unaltered patches.