Native Fish Diversity Research Articles

Environmental DNA captures native and non-native fish community variations across the lentic and lotic systems of a megacity.

Globally, urbanization poses a major threat to terrestrial biodiversity, yet its impact on fish diversity is poorly understood, mainly because of surveying difficulties. In this study, environmental DNA metabarcoding was used to survey fish communities at 109 lentic and lotic sites across Beijing, and how environmental variables affect fish biodiversity at fine urban spatial scales was investigated. We identified 52 native and 23 non-native taxa, with lentic and lotic waters harboring both common and habitat-specific species. Water quality strongly affected native fish diversity, especially in lentic systems, but had little influence on non-native diversity. Fish diversity showed little response to urban land cover variation, but the relative sequence abundance of non-natives in lotic waters increased linearly with distance from the city center. Our findings illustrate the complex effects of urbanization on native versus non-native fishes in different aquatic habitats and highlight the distinctive considerations needed to conserve urban aquatic biodiversity.

Impact of alien fishes on the distribution pattern of indigenous freshwater fishes of Punjab, Pakistan.

Pakistan is the country with mega freshwater fish diversity of native and alien species. In the presence of enormous native fishes varies species of exotic fishes have been introduced into the freshwater bodies of Pakistan which are competing with native freshwater fish fauna and making them deprive of food and habitat as well. Intentional or accidental introductions of animals, plants and pathogens away from their native niche is considered as major leading problem for biodiversity of invaded habitat. Three years study (from January 2017 to December 2019) was conducted in freshwater bodies of Province Punjab, Pakistan. Study was designed to know exotic species impacts on the distribution of native species of fishes. During current survey a total of 68 (indigenous and exotic) fish species belonging to 14 families were recorded from head Qadirabad, head Baloki, Islam headworks and Rasul barrage. Statistical analysis showed that Shannon-Wiener diversity index was the highest (1.41) at both Rasul barrage and Islam headworks but, invasive species were present in very less number in these study sites i.e. Oreochromis mozambicus, O. niloticus, Hypophthalmichthys nobilis, Carassius auratus, Ctenophryngdon idella, Cyprinus carpio and H. molitrix. The diversity index showed that comparatively low diversity was present in both area head Qadirabad (1.30) and head Baloki (1.4) due to high pressure of invasive species. Direct observation of species and statistical analysis showed that aliens' species produced negative impact on the local fish fauna diversity, evenness, and numbers. It is concluded that many factors are impacts on the diversity of native fishes, but alien (invasive) species also play a major role to reduction of native species, because aliens' species produce competition for native species. So it is urgent need to analysis the aliens and native food web and roosting sites in Pakistan, in future.

Evaluating the diversity of native ornamental fishes in Dong Nai biosphere reserve, Dong Nai province, Vietnam

This study was conducted from May 2019 to December 2020 to investigate the diversity of native ornamental fishes in Dong Nai Biosphere Reserve (DNBR). The study identifed 116 fish species belonging to 11 orders and 28 families in the water bodies of the DNBR. The analysis of compilation of the samples in the study further revealed that Cyprinidae was the most abundant family contributing 50 species followed by Perciformes and Siluriformes providing 24 species and 21 species, respectively. Out of 116 recorded species, 53 species were considered as ornamental fish, 77 species as food fish and 31 species as both ornamental and food fish. Among the ornamental fish group, many species have recorded good abundance at studied sites. Most of these fish species are high demand and sold at high prices in the domestic and international markets. The domesticated results showed that 21 ornamental fish species belong to 11 families were adapted and developed well in captivity conditions. The results also specified that eight species reach level 4 of domestication indicating truly domesticated, while the remaining 13 species belong to the first three levels of domestication, implying need to be further domesticated before being marketed. In addition, the study concluded that if managed sustainably, the collection of wild fish for the ornamental fish purpose could provide a stable income and livelihood for communities in the DNBR.

Fish grazing enhanced by nutrient enrichment may limit invasive seagrass expansion

The success of invasive macrophytes can depend on local nutrient availability and consumer pressure, which may interact. We therefore experimentally investigated the interacting effects of nutrient (nitrogen and phosphorus) addition, the exclusion of large herbivorous fishes and mimicked grazing on the expansion rates of the invasive seagrass Halophila stipulacea. The experiments were established on Bonaire and Aruba, two islands in the southern Caribbean, which differ in fish community structure. We observed that multiple Caribbean fish species feed on H. stipulacea. At both study sites, nutrient enrichment decreased invasive leaf carbon:nitrogen ratios. However only on Bonaire, where herbivore fish abundance was 7 times higher and diversity was 4.5 times higher, did nutrient enrichment result in a significant reduction of H. stipulacea expansion into native Thalassia testudinum meadows. This effect was likely due to increased herbivory on nutrient enriched seagrass leaves, as we found that excluding large herbivorous fish (e.g. parrotfish) doubled invasive expansion rates in bare patches on Bonaire. On Aruba, H. stipulacea expansion rates were higher overall, which coincided with lower abundances and diversity of native fishes, and were limited by mimicked fish grazing. We suggest that top-down control by the native fish community may counteract eutrophication effects by increased grazing pressure on nutrient-rich invasive seagrass leaves. We conclude that diverse and abundant herbivore communities likely play an important role in limiting invasion success and their conservation and restoration may serve as a tool to slow down seagrass invasions.

How fast is too fast? Water velocity differentially affects growth of four Gila River, native cyprinids

AbstractUnderstanding trade‐offs associated with occupying various aquatic habitats provides a mechanistic understanding of habitat needs that can be used to evaluate the consequences of habitat loss or alteration. We used instream enclosures and field observations to identify how velocity affects the growth rates of four native species in the upper Gila River basin: longfin dace (Agosia chrysogaster) and speckled dace (Rhinichthys osculus), two species of no conservation concern, and loach minnow (Tiaroga cobitis) and spikedace (Meda fulgida), two federally endangered species. Elevated velocity was predicted to increase food delivery through drift or stimulation of benthic primary production. Energetic costs of high‐velocity habitat were predicted to vary with morphology and behaviour and be lowest for speckled dace and loach minnow because they are adapted to occupy interstitial spaces of the substrate in riffles. Spikedace and longfin dace should perform best in moderate velocities, where the trade‐off between exposure to drifting macroinvertebrates outweighs the energetic costs of maintaining position in the water column. Growth rates of loach minnow and speckled dace increased in higher velocities, but contrary to our initial predictions, spikedace growth rates also increased in high‐velocity habitats while longfin dace grew fastest in low‐velocity habitats; similar to the locations these species occupied based on field observations. These results indicate that for spikedace, the increased abundance of drifting macroinvetebrates in high‐velocity habitats outweighs the energy expenditure, but for longfin dace the energetic costs of occupying moderate to high‐velocity habitats outweigh the benefit to increased food availability. Our experiment provides a mechanistic understanding of habitat requirements across species and may inform predictions on how modifications or restoration of riverine ecosystems influence native fish diversity.

The Silent Threat of Non-native Fish in the Amazon: ANNF Database and Review

Non-native fish (NNF) can threaten megadiverse aquatic ecosystems throughout the planet, but limited information is available for the Amazon Region. In this study we review NNF data in the Amazonian macroregion using spatiotemporal records on the occurrence and the richness of NNF from a collaborative network of 35 regional experts, establishing the Amazon NNF database (ANNF). The NNF species richness was analyzed by river basin and by country, as well as the policies for each geopolitical division for the Amazon. The analysis included six countries (Brazil, Peru, Bolivia, Ecuador, Venezuela, and Colombia), together comprising more than 80% of the Amazon Region. A total of 1314 NNF occurrence records were gathered. The first record of NNF in this region was in 1939 and there has been a marked increase in the last 20 years (2000–2020), during which 75% of the records were observed. The highest number of localities with NNF occurrence records was observed for Colombia, followed by Brazil and Bolivia. The NNF records include 9 orders, 17 families and 41 species. Most of the NNF species are also used in aquaculture (12 species) and in the aquarium trade (12 species). The most frequent NNF detected were Arapaima gigas, Poecilia reticulata and Oreochromis niloticus. The current data highlight that there are few documented cases on NNF in the Amazon, their negative impacts and management strategies adopted. The occurrence of NNF in the Amazon Region represents a threat to native biodiversity that has been increasing “silently” due to the difficulties of large-scale sampling and low number of NNF species reported when compared to other South American regions. The adoption of effective management measures by decision-makers is urgently needed and their enforcement needed to change this alarming trend and help protect the Amazon’s native fish diversity.

Effect of non-native species on taxonomic and functional diversity of fish communities in different river types

Recent researches suggest that functional diversity represents the response of communities to environmental alterations better than taxonomic diversity. However, there is scarce information about how the functional diversity of freshwater fishes is affected by habitat type and the dominance of non-native species. To address this question, we analysed a large database containing 15 morpho-functional traits of 61 fish species from the Pannon Biogeographic region (Hungary). Based on a fish faunistic list and relative abundance of taxa, we quantified the taxonomic and functional diversity of riverine communities for > 700 sites of six habitat types. We asked how non-native fishes affected the taxonomic and functional diversity in different river types and at the local scale (i.e. at the site level), and how the diversity measures of native fauna elements changes along the invasion gradient. Our results showed that both functional and taxonomic richness increases with habitat complexity, from small headwater streams to large rivers. Therefore taxonomic diversity served as a good proxy for functional diversity along the environmental gradient of river types. Non-natives showed considerable functional diversity relative to their species number in each habitat type. Diversity values of native fauna elements initially increased, and then showed a major decrease along the invasion gradient. River type-specific evaluations highlighted the importance of considering the proliferation of invasive species based on both taxonomic and functional diversity indices. We argue that type-specific action plans are needed in conservation management to preserve the taxonomic and functional diversity of native fishes in Hungary, but also elsewhere.

Establishment and impact of exotic Cyprinus carpio (Common Carp) on native fish diversity in Buxar stretch of River Ganga, India

Abstract The catch pattern of the exotic Common Carp (Cyprinus carpio) and their relationship with water quality along with maturity status of fishes were assessed during 2017-2019 to understand overall establishment and impact of the species in Buxar stretch of River Ganga in West Bihar, India. A total of 64 fish species were recorded including two exotic fishes (C. carpio and Oreochromis niloticus) from the river stretch during the study period. The annual production data depicted Cyprinus carpio to be the most dominating fish species encountered from the study area sharing 57.07% (by weight) during the period 2017-19. Calculated average ‘Invasion coefficient index (Ix)’of 0.25 in entire three-year study period revealed that the invasion has moderately impacted the indigenous fish diversity. Landing of Indian Major Carp (IMC) indicated severe decline (76.4 - 95.6%) in comparison to the catch data recorded earlier from Buxar. Data generated on sex structure of Common Carp indicated that the overall sex ratio showed positive recruitment within the smaller size range of 282-307 mm and thus avails a competitive breeding advantage over other carp fishes. Gut content of Common Carp from the stretch observed major share of phytoplankton (81.04%) and zooplankton (17.18%) and thus there are significant dietary overlap of Common Carp with other valuable species. The stretch has been impacted with anthropogenic loading as identified through significantly higher water specific conductivity (580 µScm-1), Biochemical Oxygen Demand (3 mgl-1), etc. in drastically reduced water discharge regime. Among different water parameters, river flow, Biochemical Oxygen Demand and Total Phosphate showed positive whereas specific conductivity showed negative correlation with Common Carp seasonal abundance. Future conservation management measures may be formulated keeping in view of the identified factors through the present study for reducing the impending risks of the invasive fish species in Buxar stretch of River Ganga.

Combining paleolimnological proxies to understand the long-term social-ecological interactions: A case study in the Erhai basin, Southwest China

Understanding social-ecological interactions is a major research priority for sustainable management. However, the scarcity in multi-decadal records represents a big gap in information that hinders the development of above research. In this paper, we propose a framework to explore the long-term dynamic mechanisms between social and ecological systems, and present a case study in the Erhai basin, southwest China. Using paleolimnological proxies to reconstruct the long-term trends of ecological changes, the social-ecological system (SES) framework links the variations of ecosystem services (ESs) and ecosystem functions with social policies. According to the results of the Erhai basin, there were increasing social demands and wanted provisioning ESs but degraded ecosystem functions over the last 70 years. Typically, the introduction of four major Chinese carps since the 1950s, the construction of hydropower stations on the Xi'er river since the 1970s, and the development of tourism since the 1990s, have been implemented to meet the social demands for wanted fish provisioning, hydroelectricity provisioning, and culture services respectively. Although there were temporary benefits in above desired services, improper strategies have gradually impaired the functions of native fish diversity, hydrodynamic forces, and nutrient cycling. Degraded ecosystem functions threatened the sustainable provision of wanted ESs, which motivated the implementation of subsequent social policies, such as the fishing ban after the 1950s, water level control after the 1970s and restoration projects after the 1990s. By rounds of renewed social drivers/policies, the social system and ecosystem in the Erhai basin are tightly connected in the form of a feedback loop in the SES, rendering dynamic changes in wanted ESs. The current social-ecological trap in the Erhai basin emphasizes the significance of SES framework and advantages of a paleolimnological approach in revealing the long-term SES dynamics, which can help tailor proper management measures in the future.

Molecular assessment of native fish diversity in UNESCO heritage site, Tasik Raban, using DNA barcoding

Freshwater species are the most threatened group to be assessed to date by the IUCN. Freshwater fish has enormous importance as animal protein supplies for human, and it is estimated that 6% of the world annual animal protein supplies come from freshwater fishes. Barcoding projects have been initiated all over the world and the field is constantly growing. In Malaysia however, the field has not been deeply investigated and not many barcoding projects have been undertaken especially for freshwater fishes. The aim of our study is to support the progress of DNA barcode project, especially for inland reservoirs like Tasik Raban, Perak. A Standard methodology using Cytochrome c oxidase subunit 1 (COI) marker was developed to ensure native fishes are barcoded taxonomically and molecularly and ready to be accessed through online databases. Such public references can help increase awareness on local fish diversity management. Information on taxonomy and molecular characterization can be used to plan further conservation programmed especially for depleted, unrecognized, and cryptic native species.

The longest fragment drives fish beta diversity in fragmented river networks: Implications for river management and conservation

Connectivity plays a crucial role in maintaining the structural and functional attributes of river networks. Therefore, the loss of connectivity (fragmentation) alters the functioning and diversity patterns of the biota at local and regional scales. The global hydropower boom is one of the main drivers of river network fragmentation, with significant effects on the diversity of riverine biota. Analyses of beta diversity of fish assemblages in rivers with different degrees of fragmentation can give new insights into mechanisms that contribute to the responses of these assemblages to fragmentation.Here, fish beta diversity within six river networks of central Chile with different levels of fragmentation was studied to assess the responses of fish assemblages to fragmentation. A hypothesis of a significant effect of fragmentation on the beta diversity of native and non-native fish in riffles and pools was tested. This effect is expected to be modulated by both changes in environmental heterogeneity and direct obstruction of natural dispersal routes.Beta diversity based on variation of assemblage structure and environmental heterogeneity showed significant differences among river networks. Fish beta diversity showed a clear response to fragmentation in recently fragmented rivers. Specifically, the beta diversity of native fishes in pools and non-native fishes in riffles decreased with increase of the ratio between the longest non-fragmented sections of the river network to the total length of the network. These effects of fragmentation on fish assemblages were modulated by the biological features of each species, and open-water species were most severely affected.These results have significant implications for planning of the placement of new barriers in river networks subjected to hydropower boom. Planning of the placement of new barriers should consider the maintenance of long, connected sections within river networks in order to minimise the effects of fragmentation on fish biodiversity.

Multiple stressor effects on alpha, beta and zeta diversity of riverine fish

We examined the effects of regional scale land use and local scale environmental and biotic stressors on alpha, beta and zeta diversities of native fish communities in wadeable streams and non-wadeable rivers in the Danube basin, Hungary. Relationships among land use and local scale environmental and biotic stressors were weak both in streams and rivers, suggesting that these stressors act relatively independently. Alpha diversity decreased strongly with increasing local scale environmental stressor intensity in rivers. On the contrary, its response to stressors was more obscure in streams, where the best-fit statistical model indicated the importance of the interaction between land use, local scale environmental and biotic stressors, while the secondly ranked model highlighted the negative impact of local scale environmental stressors. Analysis of variance using distance matrices provided evidence that stressors alone and in interactions explained compositional differences of pairs of study sites (beta diversity). Considering the degree of overall degradation, both local (alpha) and among-site (beta and zeta) diversity indices responded to increasing stressor intensity, generally negatively. Riverine fish communities showed higher degrees of similarity (lower beta and higher zeta) than stream fish communities. They also showed increasing similarity (i.e. homogenization) with increasing overall stressor intensity, unlike stream fish communities, which showed no relationship with overall stressor intensity. Our results suggest that the relationships between land use and local scale environmental and biotic stressors can be complex and so do their effects on biodiversity. While stressor specific indices can provide information on the role of specific stressors in some cases, the examination of overall stressor effects is needed to assess realistically the effects of anthropogenic disturbances on native fish diversity. Diversity indices that quantify among-site changes in species composition, such as measures of beta and zeta diversity, can be fruitful for better understanding the role of multiple stressors in structuring ecological communities.

Use of a novel richness-weighted abundance index of age-0 fishes to identify key features for habitat conservation and restoration

Prioritizing sites for conservation or setting goals for enhancement and restoration projects is often difficult due to limited knowledge about relations between habitat characteristics and faunal assemblages. We tested the utility of a novel richness-weighted abundance (RWA) index as a tool for guiding habitat conservation and restoration for native fishes and compared its utility to established indices of abundance and diversity (i.e., Shannon diversity index, Simpson diversity index, species richness, total catch). Habitat and fishes were sampled in the upper Niagara River during late summer, 2013–2015. We used multivariate adaptive regression splines to model the relation between each index of abundance or diversity of native age-0 fish and aquatic habitat features, and compared R2 values among models to determine the strength of the relationship between each index and aquatic habitat features. Our RWA index had the strongest relation with habitat features (R2 = 0.40) and Shannon and Simpson indices were unrelated to habitat features. We found the best habitats for native fishes (i.e., highest RWA scores) contained substantial submerged aquatic vegetation extending into the water column (>20%), low water velocities (<0.1 m/s), and fine to very fine substrates. Our approach of valuing habitat based on an RWA index allows researchers and practitioners to assess the quality of native fish assemblages and determine which habitat characteristics are associated with supporting those assemblages. This index should be applicable to other ecosystems, and has value for ranking existing sites for conservation and for setting clear goals for enhancement and restoration projects.

European minnows through time: museum collections aid genetic assessment of species introductions in freshwater fishes (Cyprinidae: Phoxinus species complex)

Massive fish introductions have taken place throughout much of the world, mostly over the last 70 years, and present a major threat to the genetic diversity of native fishes. Introductions have been reported for European Phoxinus, a ubiquitous small cyprinid that populates a wide variety of habitats. Species delineation in European Phoxinus has proven difficult with one reason being ranges of distribution that often traverse drainage boundaries. The present study combines recent samples with museum samples to better understand the current distribution of Phoxinus species and their distributions prior to the massive introductions of fishes in Europe, and to evaluate the use of museum specimens for species distribution studies. For these purposes, genetic lineages from sites collected prior to 1900 (n = 14), and between 1900 and 1950 (n = 8), were analysed using two mitochondrial and nuclear markers. Although possible fish introductions were detected, our results show that the distribution of genetic lineages of museum samples is comparable to that of the extant lineages of European Phoxinus present in those areas. These observations suggest that in the studied ranges the distribution of Phoxinus lineages has been driven by natural processes.

Impact of the non-native locariid fish Pterygoplichthys pardalis in native fish community on a seasonal tropical floodplain in Mexico

The present study reports the seasonal dynamics of the fish community structure in the presence of a non-native fish (Pterygoplichthys pardalis) in tropical waterbodies of southern Mexico. The studied floodplain existed in both connected pools and disconnected pools “to the Palizada river”. Local fish fauna showed consistent assemblages across seasons, but among the 17 local fish species recorded, the non-native species P. pardalis showed the highest percentage of contribution to the fish community (ca. 20%). Conversely, the frequency of occurrence and density of the non-native species showed variation in relation to the type of waterbody and seasonality; its density was approximately four times higher in disconnected pools than in connected pools in the rainy season and its predominant size class in both pool types was 21-30 cm in standard length. Interestingly, the diversity of the native species was negatively related to the density of the non-native species, indicating that the presence of P. pardalis can be a factor involved in the decline of native fish diversity in these local communities. Currently, the possible impacts of the presence of P. pardalis on local fish diversity at the regional scale are unknown, but our results suggest that hydrological dynamics regulate the establishment of the non-native species in this region. However, future studies are needed to provide insights into the actual scenario of P. pardalis distribution in Yucatan Peninsula and the possible impacts on the native fish fauna in southern Mexico.

Dynamic contributions of intermittent and perennial streams to fish beta diversity in dryland rivers

AbstractAimTo determine the role of flow intermittence and species origin in shaping freshwater fish beta diversity across dryland riverscapes.LocationVerde and Little Colorado River basins, United States.MethodsFish beta diversity was investigated in two large rivers with marked differences in basin‐wide flow intermittence. Local site (continually flowing perennial vs. periodically flowing intermittent) and species (native vs. non‐native) contributions to beta diversity were compared within each basin and over multiple decades (1987–2013) in relation to changing hydrologic conditions. Metacommunity dynamics were quantified using changes in alpha‐ (local), beta‐ and gamma‐ (regional) diversity through time.ResultsBeta‐diversity patterns varied in relation to basin‐wide intermittence. Intermittent sites were most influential to beta diversity where basin‐wide intermittence was lower (Verde River), whereas perennial sites were most influential where basin‐wide intermittence was higher (Little Colorado River). In intermittent sites, native fish species contributions to beta diversity tended to be higher than non‐native species contributions. The relative contributions of perennial and intermittent sites to β‐diversity within each basin were invariant to annual flow regimes, whether atypically lower or higher than average flows, but somewhat related to intra‐annual flow variation. Native species contributions to β‐diversity increased in years with high flow conditions in the Verde River. Over time, beta diversity decreased in the lower intermittence Verde River, indicating taxonomic homogenization, but remained relatively unchanged in the Little Colorado River.Main ConclusionsInvestigations of beta‐diversity components over time are considered pivotal for conservation prioritization and planning. We found that both intermittent and perennial streams play complementary roles in supporting fish beta diversity, and that their relative contributions increase as basin wide availability of the habitat type decreases. Moreover, contributions of intermittent streams to overall beta diversity were relatively consistent through time and supported native fish diversity. Despite weakening policy protections of intermittent streams, these habitats are critical for supporting local species persistence and regional biodiversity.

Congruence in riverine conditions and associations between native fish and several species of amphibians in a region prone to fish invasions

The relationship between fish and amphibians is thought to be antagonistic because of the frequent amphibian extirpations after fish introductions, although some field observations show that amphibians and fish often co-occur in rivers. Here, we used surveys in north-eastern Spain (99,700 km2, 15 river catchments, N = 535 sites) to identify the most frequent fish–amphibian associations and the riverine conditions that might concurrently promote the diversity of native fish and of five widely distributed amphibian species. Overall, there was little congruence between native fish and amphibian-diversity measures (species richness and the Shannon, Simpson and Pielou diversity indices). Different riverine conditions appeared to be important for the two vertebrate groups. Alien fish richness, which was highly correlated with alien fish abundance, was negatively associated with amphibian richness and Shannon diversity but was positively associated with native fish richness. River water depth was negatively associated with amphibian occurrence. While our snap-shot surveys may be a transitional stage in the fish–amphibian relationships, we found that some widely distributed amphibian species co-occur with fish in rivers in north-eastern Spain. Small rivers, such as tributaries often have the most intact fish assemblages, and probably are the best locations to explore fish–amphibian associations in greater depth.

Diversity patterns of native and exotic fish species suggest homogenization processes, but partly fail to highlight extinction threats

AbstractAimExotic species are a major threat to biodiversity and have modified native communities worldwide. Invasion processes have been extensively studied, but studies on species richness and beta diversity patterns of exotic and native species are rare. We investigate such patterns among exotic and native fish communities in upland and lowland rivers to explore their relationship with environmental drivers.LocationNorthern Italy.MethodsExotic and native fish beta diversity patterns were investigated separately in lowland and upland sites using Local Contribution to Beta Diversity (LCBD) and Species Contribution to Beta Diversity (SCBD) analyses. To examine the main environmental variables affecting the LCBD, a Boosted Regression Trees (BRT) method was used. Community dispersion among and within stream orders was investigated with the PERMDISP test.ResultsIn lowland sites, exotic species richness was higher than native species richness, especially in large rivers and drainage canals. An opposite trend was found in upland sites, where native species richness was higher than exotic species richness, especially in large rivers. No clear LCBD patterns were found along stream orders in the lowland, whereas higher stream orders in the upland showed the highest LCBD. Its patterns in upland and lowland sites were related to a number of factors, such as total suspended solids and total phosphorus. Community dispersion among stream orders did not show a relationship with environmental heterogeneity. SCBD values were positively correlated with species occupancy in the study area, and native species showed higher SCBD values than exotic species only in the uplands.Main conclusionsLarge rivers in the uplands are important in maintaining native fish diversity and should be protected against invasive fish. In contrast, most lowland rivers have suffered from biological homogenization. Some rare native species can show low contribution to beta diversity, but still need conservation actions due to their risk of local extinction.

Understanding spatial and temporal patterns of fish diversity and assemblage structure vis-a-vis environmental parameters in a tropical Indian reservoir.

Reservoirs have been given priority as an important resource for fisheries enhancement in inland open waters. This paper described the spatial and temporal pattern of fish diversity using GIS platform, assemblage structure, and studied the influence of environmental parameters in these variables in a large tropical reservoir, Chandil, located in the eastern India using multiple approaches. Altogether, 42 fish species belonging to 30 genera were recorded from the reservoir, including two exotic species: pangas, Pangasianodon hypophthalmus, and Nile tilapia, Oreochromis niloticus. The diversity indices indicated lowest fish diversity in the lacustrine zone, but without distinct seasonal variation. The taxonomic distinctness was lower in the lacustrine zone as compared to other zones, and the summer season exhibited higher taxonomic distinctness, though the number of species was lowest. Most of the physicochemical parameters recorded are within the favorable range for fisheries enhancement. Among the environmental parameters, pH and nitrate significantly influenced the fish abundance. The study recommends suitable measures and interventions for conservation of the native fish diversity and sustainable fisheries development: closed season, protected/conservation area, introduction of fish aggregating device (FAD), and regulated fish culture in enclosures.

Native larvivorous fish diversity as a biological control agent against mosquito larvae in an endemic malarious region of Ranchi district in Jharkhand, India

Mosquitoes are responsible for transmitting several diseases, including malaria, dengue, chikungunya, filariasis, and yellow fever, etc. Release of larvivorous fishes is one of the cheapest method of vector management approach, with long suppression of mosquito population. The present study identifies the native larvivorous fishes and evaluates their potential larvivoracity for biological control of mosquito larvae in an endemic malarious region. During the year 2012-13, an ecological descriptive study was carried out in diverse aquatic habitats of fish species found in different areas of Ranchi district, in Jharkhand state of India. Fishes were captured using fishing nets, and identified and classified according to the available keys. Their larvivorous potential was graded according to their feeding potential. Data on current conservation status as well as their abundance were also recorded and analysed. In total, 30 larvivorous fish species belonging to seven orders, 10 families and 21 genera were identified. Order Cypriniformes and the family Cyprinidae were the most ascendant group constituting 66.7 and 60%, respectively. The grading assessment of larvivorous potential for different fish species revealed that, Colisa fasciatus possess maximum larvivoracity (+ + + + +). According to the conservation, assessment and management plan (CAMP, 1998), 60% species were at lower risk near threat (LRnt), while 86.7% species were at least concerned (LC) as per the IUCN, 2017 categorisation. All fish species preferred to inhabit in freshwater. Maximum species occurrence was found in the river (63.3%). Only 30% species were bottom feeders (BF). The larvivoracity and habitat distribution analysis indicated that C. fasciatus, Oreochromis mossambica, Esomus danricus, Oryzias melastigma, Puntius sophore, P. ticto, Rasbora daniconius, R. elegans, Aplocheilus panchax, and Danio (B) rerio possess high-level larvivorous potentiality in nature and are recommended for malaria control in the study area. There is an increasing pressure on the fish fauna, of facing several threats, such as fishing, human interference, loss of habitat, overexploitation, pollution, siltation, trade, and diseases. Therefore, periodic survey and monitoring of fish biodiversity, demarcation of breeding sites, field level research study on the efficacy of these fishes, and public awareness on establishment of larvivorous fish ponds should be adopted as a part of the vector management approach in the endemic malarious region of Ranchi district in Jharkhand, India.