Fish Species Richness Research Articles

Habitat Provision and Erosion Are Influenced by Seagrass Meadow Complexity: A Seascape Perspective

Habitat complexity plays a critical role in shaping biotic assemblages and ecosystem processes. While the impacts of large differences in habitat complexity are often well understood, we know less about how subtle differences in structure affect key ecosystem functions or properties such as biodiversity and biomass. The late-successional seagrass Posidonia australis creates vital habitat for diverse fauna in temperate Australia. Long-term human impacts have led to the decline of P. australis in some estuaries of eastern Australia, where it is now classified as an endangered ecological community. We examined the influence of P. australis structural complexity at small (seagrass density) and large (meadow fragmentation) spatial scales on fish and epifauna communities, predation and sediment erosion. Fine-scale spatially balanced sampling was evenly distributed across a suite of environmental covariates within six estuaries in eastern Australia using the Generalised Random Tessellation Structures approach. We found reduced erosion in areas with higher P. australis density, greater abundance of fish in more fragmented areas and higher fish richness in vegetated areas further from patch edges. The abundance of epifauna and fish, and fish species richness were higher in areas with lower seagrass density (seagrass density did not correlate with distance to patch edge). These findings can inform seagrass restoration efforts by identifying meadow characteristics that influence ecological functions and processes.

Changes in taxonomic and functional diversity of an urban stream fish assemblage: A 30-year perspective

Globally, freshwater fish diversity is rapidly changing in response to land use change, including urbanization. Time series of freshwater fish communities can help elucidate the underlying mechanisms of species loss and gains, as well as promote conservation strategies. Traditional approaches to understand the dynamics of fish assemblages is traditionally focused on taxonomic diversity, one aspect among many dimensions of biodiversity. Thus, using complementary analytical methods, such as functional diversity, can help researchers to develop a stronger predictive framework on the effects of the species loss or gains in response to urbanization. We assessed temporal changes of fish assemblages in an urban stream in East Texas between four seasonal surveys of 1989–1990 and 2018–2019. We explored the similarities and differences in species richness, composition, and functional diversity of fishes. Although the species richness and functional richness between the two time periods were similar, we observed changes in species composition. We also observed higher functional dispersion and evenness in the 2018–2019 assemblage compared to 1989–1990 assemblage. Some fish species were locally extirpated, while others colonized the system, increasing the functional diversity of the current assemblage. Urbanization has commonly been associated with declines in diversity and richness, however, our findings suggest that the addition of a few invasive generalist species (e.g., blue tilapia) and native tolerant (e.g., redbreast sunfish, blacktail shiner) in this stream system could be associated with increased human activities in this small, urbanized area in East Texas. Streams in East Texas support very diverse fish assemblages, with some sentinel species (e.g., imperiled shiners: Sabine shiner, a habitat-affinity, broadcast spawner) rapidly responding to stream alterations. Multiple stressors can underlie the dynamics and composition of fish assemblages; thus, it is essential for more comparative studies of current and historical data of fish assemblages. Likewise, studies targeting sentinel fish species may have more utility for the evaluation of freshwater ecosystems.

Patterns in and predictors of stream and river macroinvertebrate genera and fish species richness across the conterminous USA.

Both native and non-native taxa richness patterns are useful for evaluating areas of greatest conservation concern. To determine those patterns, we analyzed fish and macroinvertebrate taxa richness data obtained at 3475 sites collected by the USEPA's National Rivers and Streams Assessment. We also determined which natural and anthropogenic variables best explained patterns in regional richness. Macroinvertebrate and fish richness increased with the number of sites sampled per region. Therefore, we determined residual taxa richness from the deviation of observed richness from predicted richness given the number of sites per region. Regional richness markedly exceeded average site richness for both macroinvertebrates and fish. Predictors of macroinvertebrate-genus and fish-species residual-regional richness differed. Air temperature was an important predictor in both cases but was positive for fish and negative for macroinvertebrates. Both natural and land use variables were significant predictors of regional richness. This study is the first to determine mean site and regional richness of both fish and aquatic macroinvertebrates across the conterminous USA, and the key anthropogenic drivers of regional richness. Thus, it offers important insights into regional USA biodiversity hotspots.

Evidence of fish community fragmentation in a tropical river upstream and downstream of a dam, despite the presence of a fishway

Context Rapid human population growth has increased demand for water supply, food security, electricity, and flood mitigation worldwide. To address these challenges, governments have invested heavily in the expansion of water infrastructure. However, there is substantial evidence that globally, this infrastructure impacts aquatic ecosystems and can have a significant impact on the persistence of fish species. Despite being well understood globally, the impacts of dams on fish have been given scant attention in Indonesia. Thus, considerations for fish are rarely included in river development planning frameworks. Methods To document the impact of riverine barriers on Indonesian freshwater fish, we surveyed multiple sites, using three different kinds of gear (gillnets, castnets, and bait traps), upstream and downstream of Perjaya Dam in the Komering River. Key results The study revealed 13 of 36 species were found only downstream of the dam and five of 36 species were found only above the dam. There were significant differences in fish community composition between upstream and downstream regions using either fish abundance (Pseudo-F = 4.495, d.f. = 1, P < 0.05), species richness (Pseudo-F = 15.837, d.f. = 1, P < 0.05) or species diversity as the response metrics (Pseudo-F = 8.3256, d.f. = 1, P < 0.05). Conclusions The local extirpation of many species from upstream areas suggests that the Perjaya Dam hinders fish migration. Implications Despite containing a fishway, the results indicate that fish are not successfully recolonising upstream reaches.

The Spatial and Temporal Disparity of Fish Assemblage and Its Association with Environmental Factors Through Multivariate Statistical Analysis in Jammu and Kashmir's Himalayan River System.

The goal of this study was to explore the dynamics of the environmental components with fish species assemblages in the Ravi and Chenab rivers of the Himalayan river system during the study period from "July 2020 to June 2021".. To examine the relationship between fish species and environmental parameters, multivariate statistical analyses including canonical correspondence analysis, principal component analysis and cluster analysis were applied to data from fish species. ANOSIM and SIMPER were used to determine whether fish assemblage varied with seasons or streams and to identify the fish species that contributed to this variation between the sampling sites. To study the effect of environmental factors on fish species richness, multiple regression analysis was used. Fish species belonging to 30 species and 12 different families (Cyprinidae, 66.6%) were recorded from three study sites (Bhini, Jhajjar and Chadwal streams) with Chadwal (34.3%) having the most ichthyofaunal population. Hillstream fish species dominated the Bhini stream, while catfish species dominated the Jhajjar stream. The Chadwal Stream was home to a diversity of fish species due to its vast fishing grounds. The values of free carbon dioxide (FCO2), bicarbonates (HCO3-), and habitat structure showed significant variations (p<0.05). The Shannon-Wiener (H'), Simpson dominance, and Margalef index values of fish communities were high. Differences in environmental parameters in each sampling site influenced the fish population in the present study. Our findings showed that environmental factors influenced species composition and provided evidence for the dynamic interaction between environmental variables and fish assemblage in the Ravi and Chenab rivers.

Drivers of contemporary lacustrine fish species richness in the glacial Lake Agassiz basin

AbstractAimBiological communities are the result of a stepwise spatiotemporal filtering process, driven by large‐scale historical and local contemporary determinants. The biogeographical pattern and species richness of North American fishes are predominantly determined by historical processes of past glaciations and postglacial dispersal and by contemporary environmental and ecological processes. We evaluated the effects of postglacial dispersal through glacial Lake Agassiz and habitat heterogeneity, represented by lake surface area, on contemporary freshwater fish species richness patterns of northwestern Ontario lakes.LocationNorthwestern Ontario, Canada.TaxonFreshwater fishes.MethodsApplying the theory of island biogeography and species–area curves, we examined the effects of isolation from the past dispersal corridor of glacial Lake Agassiz and habitat heterogeneity on species richness across 264 contemporary lakes. While controlling for correlations among the predictor variables, generalized linear models were constructed between species richness, as the response variable and the explanatory variables of lake elevation and surface area, and connection to the dispersal corridor.ResultsDifferential cover by glacial Lake Agassiz led to variation in fish species richness across contemporary lakes and it is higher in lakes that were covered by Lake Agassiz relative to basins remaining outside of the boundaries of the glacial lake. Lake surface area is the strongest predictor of species richness, while lake elevation is the strongest factor predicting isolation.Main ConclusionsHabitat heterogeneity and postglacial colonization have led to differences in fish richness within the same geographical region, which increases with lake surface area and decreases with elevation. These are likely driven by greater niche diversity facilitating the assembly of more diverse communities and isostatic rebound and fluctuating levels of Lake Agassiz isolating lakes at high elevations from the dispersal route earlier during the colonization process, respectively. These patterns underscore the importance of incorporating historical and environmental community determinants in biodiversity studies.

A Geospatial Approach to Improving Fish Species Detection in Maumee Bay, Lake Erie

Maumee Bay of western Lake Erie is at high risk for invasion by aquatic invasive species due to large urban and suburban populations, commercial shipping traffic, recreational boating, and aquaculture ponds. The U.S. Fish and Wildlife Service’s Early Detection and Monitoring (EDM) program has been monitoring for new invasive species since 2013 and is continually looking to adapt sampling methods to improve efficiency to increase the chance of detecting new aquatic invasive species at low abundances. From 2013–2016, the program used a random sampling design in Maumee Bay with three gear types: boat electrofishing, paired fyke nets, and bottom trawling. Capture data from the initial three years was used to spatially explore fish species richness with the hot spot analysis (Getis-Ord Gi*) in ArcGIS. In 2017, targeted sites in areas with high species richness (hot spots) were added to the randomly sampled sites to determine if the addition of targeted sampling would increase fish species detection rates and detection of rare species. Results suggest that this hybrid sampling design improved sampling efficiency as species not detected or were rare in previous survey years were captured and species were detected at a faster rate (i.e., in less sampling effort), particularly for shallow-water gear types. Through exploring past data and experimenting with targeted sampling, the EDM program will continue to refine and adapt sampling efforts to improve efficiency and provide valuable knowledge for the early detection of aquatic invasive species. The use of geospatial techniques such as hot spot analysis is one approach fisheries researchers and managers can use to incorporate targeted sampling in a non-subjective way to improve species detection.

Influence of In-stream Ecosystem Restoration Techniques on the Fish Ecology of the River Nabongo in Eastern Uganda

The study was the first in Uganda to assess the responses of fish community assemblages to introduced woody debris structures in a tropical river in Eastern Uganda. For comparison purposes, two different woody debris structures (simple and complex) were introduced in river Nabongo, and their effect on fish assemblage and feeding was established based on experiments conducted in two heterogeneous stream environments (a pool and a riffle). Results showed that sampling plots treated with restoration structures registered higher fish species richness, diversity, and abundance than sampling plots without restoration structures (control plots) at each site. The study (experiment) applied a stratified sampling design which used purposive identification of a pool and a riffle in River Nabongo Catchment. Fish were captured using a drift net, an electro-fishing gear, and a hand net. Data were analysed using a one-way ANOVA generated from STATA version 14. At the pool site, total fish density varied significantly from plot to plot (P<0.05) but was highest in the complex structures with 64±1.08 fishes/m2 and lowest with 24±0.82 fishes/m2 in untreated plots. K-factor did not vary significantly in untreated plots at the pool site but significantly differed from treated plots at P<0.05. The relative abundance of fish species at the pool site was highest in the complex structures with 40.7±0.66% and 21.5±0.42% before structures but was least in the control plot, varying significantly from plot to plot at P<0.05. It was concluded that woody debris restoration is an effective stream restoration technique. Fish individuals, trophic groups, and taxa more densely colonised sampling plots that had structures than those that did not have structures.

Ecological value of gravel pit ponds for floodplain wetland fish

Abstract Floodplain wetlands support high biodiversity, but they have been degraded and geographically fragmented due to human activities. Some types of human‐created waterbodies have received growing attention as alternative habitats for conserving wetland biodiversity. Gravel pit ponds (GPPs) are human‐created wetlands formed when a gravel pit is excavated at or below the water table and filled with groundwater. Differences in community structure among GPPs and floodplain wetlands with respect to habitat characteristics are scarcely known, resulting in insufficient evaluations of the ecological value of GPPs for floodplain wetland species. In this study, we evaluated the ecological value of GPPs for wetland fishes in floodplain landscapes. We surveyed fish abundance, community composition, and 10 environmental factors in GPPs and two types of floodplain ponds (remnant ponds and river backwaters) to clarify the biotic and abiotic differences among the pond types. Environmental factors were similar among the pond types, with only water temperature and the distance from the main channel to the pond significantly lower in river backwaters. The richness and abundance of native fish species did not differ among the pond types, but species composition did. Rhynchocypris percnura sachalinensis, Carassius sp., and Lethenteron sp. N (one of the two cryptic species of Lethenteron reissneri) were selected as indicator species in GPPs, remnant ponds, and river backwaters, respectively. These results indicate that GPPs provide valuable habitats for wetland fishes in floodplain landscapes and support regional γ diversity. Since many species inhabited the GPPs in this study, including red list species, appropriate management of GPPs is important to conserve wetland fishes.

The reef fish assemblage of a coral reef system in the southwestern Gulf of Mexico

Reef fish species richness of the Veracruz Reef System National Park (VRSNP) in the SW Gulf of Mexico is well known. However, the knowledge of the assemblage structure and its spatial variability in the reef ecosystem is quite limited. For that purpose, 5 field surveys (2012-2015) were performed, using the stationary visual census method, at 10 selected reefs. The most important findings were: 116 reef species were recorded. Average total reef fish density (2.31 Ind/m2) is similar to the records for the Caribbean reefs in the 20th century. The top 5 most abundant species were: Chromis multilineata, Ocyurus chrysurus, Abudefduf saxatilis, Stegastes leucostictus, and Elacatinus jarocho. We found evidence of a spatial distribution pattern with 3 well-defined groups of reefs: (1) those near the city of Veracruz, (2) those near the outlet of the Jamapa River, and (3) those farther from the city. Higher fish densities are associated to both high hermatypic coral and low crustose coralline algae bottom covers. The assemblage structure of reef fishes is different at distinct geomorphological reef zones. As expected, with some differences in the species abundance order, the assemblage structure of reef fishes is similar at all coral reefs in the Gulf of Mexico.

Continental slope fishes of the Potiguar Basin off Northeast Brazil in the Equatorial Atlantic ocean

Deep-sea fish species compose around 15% of the observed fish biodiversity, and studies concerning the ecology and distribution of these marine fish species are essential to understand the magnitude of human influence on the deep ecosystems. The western South-Atlantic deep-sea fishes are well described and began to be studied in 1873. Nevertheless, studies considering fish community structure are still scarce in this area. This present study analysed the effects of oceanographic variables on deep-sea fish assemblages structure, density and species richness. To measure diversity, interpolated and extrapolated accumulation curves were drawn using Hill numbers along the Southwest Equatorial Atlantic Ocean depth intervals. A total of 36 trawls were carried out by an otter-boarded bottom trawl net between depths of 150 and 2000 m. Fish biomass showed the highest values between 150 and 400 m, reaching the highest numbers at 400 m, with a decline in the areas of 1000 m and 2000 m. The highest species richness was seen in the shallowest areas (150 m), with a declining trend towards deeper regions. Fish assemblages and habitats' affinity, species, individual lengths, depth, coast distance, longitude and density were used to identify and quantify clusters. The caught fishes belonged to 167 species (115 demersal, 52 pelagic), distributed within 63 families and three orders. The spatial and bathymetric occurrences of some species in the present study were broadened. The most important species in 150, 400, 1000 and 2,000m depth strata were Citharichthys cornutus, Saurida caribbaea, Monomitopus americanus and Dibranchus tremendus, respectively. Assemblages were clustered in four groups; the cluster's richness values were 64, 30, 10, and 11, respectively. Clusters 1, 2 and 3 represented depth values of 150, 400 and 1000 m and overlapped in k-means, showing a more similar pattern, unlike cluster 4 (2,000m). The most profound fish assemblage varies statistically significantly by depth, density, richness and diversity. Rapoport's rule interpretations explained the negative relationship between richness, density and depth and the positive association of length and depth. Despite the highest richness in cluster 1 and the lower richness in 4, they had the lowest effective diversities (Hill numbers), cluster 3 showed the lowest richness, but it had a high evenness trend and then had the highest effective diversity.

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

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

Spatial non-stationarity in the distribution of fish species richness of tropical streams

Spatial non-stationarity in the distribution of fish species richness of tropical streams

Evidence for the cooking of fish 780,000 years ago at Gesher Benot Ya'aqov, Israel.

Although cooking is regarded as a key element in the evolutionary success of the genus Homo, impacting various biological and social aspects, when intentional cooking first began remains unknown. The early Middle Pleistocene site of Gesher Benot Ya'aqov, Israel (marine isotope stages 18-20; ~0.78 million years ago), has preserved evidence of hearth-related hominin activities and large numbers of freshwater fish remains (>40,000). A taphonomic study and isotopic analyses revealed significant differences between the characteristics of the fish bone assemblages recovered in eight sequential archaeological horizons of Area B (Layer II-6 levels 1-7) and natural fish bone assemblages (identified in Area A). Gesher Benot Ya'aqov archaeological horizons II-6 L1-7 exhibited low fish species richness, with a clear preference for two species of large Cyprinidae (Luciobarbus longiceps and Carasobarbus canis) and the almost total absence of fish bones in contrast to the richness of pharyngeal teeth (>95%). Most of the pharyngeal teeth recovered in archaeological horizons II-6 L1-7 were spatially associated with 'phantom' hearths (clusters of burnt flint microartifacts). Size-strain analysis using X-ray powder diffraction provided evidence that these teeth had been exposed to low temperature (<500 °C), suggesting, together with the archaeological and taphonomic data, that the fish from the archaeological horizons of Area B had been cooked and consumed on site. This is the earliest evidence of cooking by hominins.

Chemical fragmentation of stream systems and fish species richness: The upstream effects of water pollution

Chemical fragmentation of stream systems and fish species richness: The upstream effects of water pollution

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

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

Diversity of reef fish species in presence of mangrove habitat in Ternate, North Maluku, Indonesia

Abstract. Utama RS, Renyaan J, Nurdiansah D, Makatipu PC, Suyadi, Hapsari BW, Martha E, Rahayu EMD, Sugiharto A. Akbar N. 2022. Diversity of reef fish species in presence of mangrove habitat in Ternate, North Maluku, Indonesia. Biodiversitas 23: 5184-5193. Research on reef fish has been widely reported, where information about reef fish communities is an important factor for evaluating fisheries management and coral reef management. Mangroves as the nursery, foraging, and growing areas were also important to assure sustainable reef fish fisheries. This paper studies reef fish abundance and diversity in Ternate Waters in the presence of mangrove in coral reef habitats. To determines coral reef condition underwater photo transect was performed while an underwater visual census (UVC) was used to determine the abundance and diversity of reef fishes in Ternate waters between 2017 and 2018. A total of 14 stations were used, with eight stations near the mangroves and six stations that did not contain mangroves. Based on the observation, fish species richness in mangrove absence was higher than in the presence of mangroves, with 68 and 65 species in 2017 and 66 and 62 species in 2018. However, the abundance of reef fish was recorded high in the presence of mangroves than in the absence of mangroves, with 390 and 289 individual differences in 2017 and 2018. Mangroves' complexity affected part of reef fish communities in Ternate water, particularly Lutjanidae, Serranidae, and Scaridae, which might influence the abundance of reef fishes rather than the species richness. In addition, carnivore shows a negative effect in the presence of mangroves, in contrast with herbivores. It is related to mangrove functioning as a temporary shelter when high-pressure presence in their natural habitat (reef) and a place for foraging. Therefore, mangrove management must be a consideration in the coral reef or fisheries management program.

Environmental-related variation of stoichiometric traits in body and organs of non-native sailfin catfishes Pterygoplichthys spp.

Intraspecific variation in stoichiometric traits was thought to be an adaptive response to reduce the elemental imbalance between organism and diet in the habitat. Studying the spatial variation of stoichiometric traits of non-native species and the factors contributing to the variation could help to better understand the invasion mechanism of non-native fish. In this study, stoichiometric traits (i.e. carbon [C], phosphorus [P], calcium [Ca] and their ratios) variation in the body and organs of non-native sailfin catfishes Pterygoplichthys spp. were investigated across 13 river sections in the main river basins of Guangdong province. The relationships between environmental factors and stoichiometric traits were analyzed using a general linear model and an information-theoretic approach. A manipulated feeding experiment was conducted to investigate the impact of food quality on the stoichiometry of sailfin catfishes in a greenhouse. Sailfin catfishes exhibited considerable variability in body and organ elemental composition. Site identity was the main factor contributing to the variation, which could be explained by a combination of environmental factors including climate, diet quality, fish species richness and trophic status in the invaded rivers. Water chemistry (i.e. total nitrogen and phosphorus, ammonia nitrogen and soluble reactive phosphorus) contributed to the most variation of stoichiometric traits. Imbalances of P and Ca between sailfin catfishes and food resources varied among sampling sites, reflecting the spatial heterogeneity of nutrients limitation. Juvenile sailfin catfishes exhibited stoichiometric homeostasis (0 < 1/H < 0.25) for all elemental contents and ratios in the feeding experiment. These findings suggested variation in stoichiometric traits of sailfin catfishes might be attributed to the changes in elemental metabolism to cope with context-specific environments. This study provided heuristic knowledge about environmental-related variation in stoichiometric traits, which could enhance the understanding of the non-native species' adaptation to resource fluctuation in the invaded ecosystems.

Longitudinal fish species diversity and distribution in a medium-sized Afro-tropical river in the Lake Victoria Basin

Despite significantly influencing fisheries characteristics of major global basins, medium-sized rivers such as Awach Kibuon remain the least studied. This study evaluated longitudinal fish species diversity, distribution, and environmental influence in Awach Kibuon River, Lake Victoria Basin, Kenya, to inform sustainable management of fisheries resources within the region. Nine sites located in different zones of the river were sampled monthly for eight months in 2019 and 2020. Fish samples were collected for 45 minutes using a backpack electrofisher on a 50-m river reach in every sampling site. Selected physico-chemical parameters (pH, total dissolved solids (TDS), dissolved oxygen (DO), temperature, conductivity, and turbidity) were measured in situ using standard methods. Longitudinal river fish diversity was assessed using species richness, Simpson's Index (D), Shannon-Weiner Index (H′), and Pielou's Evenness Index (J). A total of 983 fish specimens belonging to 21 species, 12 genera, seven families, and six orders were caught during sampling. Cyprinidae was the most dominant family, represented by nine species, followed by Claridae, Mochokidae, and Cichlidae, represented by three species each. Longitudinal species richness, abundance, and diversity indices deviated from the expected downstream increase. Upstream stations had no fish, whereas midstream and river mouth stations had moderate and high species diversity, respectively. Pearson's correlation analyses showed that temperature, conductivity, TDS, depth, and velocity influenced fish species richness in the river. The above findings call for the inclusion of medium-sized rivers in fisheries management plans of Great Lakes Basins for sustainability.

Environmental Factors Associated with Fish Diversity in Two Tributaries of River Chittar, Southern Western Ghats, Tamil Nadu, India

In the present research, we examined Ichthyofaunal diversity, habitat preferences, and environmental variables in the Chittar River tributaries in Tamilnadu, India. The species composition is comprised of 14 species representing 4 orders, 6 families, and 12 genera. Cyprinids were the most abundant group in the assemblage composition of fishes, which was approximately 61.5%-83.33%. According to the Shannon-diversity index of fish populations in the study streams, the upstream of New Falls and the Harihara river reveal a high species richness. Among the recorded fish species, Puntius arenatus, belonging to the family Cyprinidae, is in the vulnerable categories of the IUCN List. However, the fish species exhibited a higher density in the headwaters upstream and the density decreased in the downstream. However, bedrock and boulders were observed as the predominant substrates in upstreams (sites 1 and 3) throughout the seasons. The results of Principal Component analysis of water quality factors and fish abundance and species richness revealed that dissolved oxygen, total hardness, and alkalinity have less impact on fish abundance, whereas TDS and conductivity had a substantial correlation in all downstreams. Fish were influenced by a diverse natural and anthropogenic longitudinal pattern, as well as regional disturbances induced by adjacent land users.