Fish Species Richness Research Articles

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.

The Evolutionary Dynamics of the Mitochondrial tRNA in the Cichlid Fish Family.

Simple SummaryCichlids are a unique example of fish diversity and species richness which have been explained by sympatric speciation at different freshwater sources in Africa. The mitochondria contribute to cell vitality by providing energy. It contains a circular genome with an established translation system that is spatially independent of the cytosolic counterpart. The current study aimed to investigate the evolutionary dynamics of the mitochondrial tRNA and its role in cichlids’ diversity. The available cichlid mitogenomes in the public database were filtered, in addition to newly sequenced accessions from a specific cichlid group known as the haplotilapiine lineage that is widely distributed in the Egyptian sector of the Nile River. Based on the comparative analysis of mitogenomic data, we identified 22 tRNA genes, in which a single gene was D-armless, while the cloverleaf secondary structure subdivided into stem-loop formations was predicted and used to define the levels of genetic divergence for the remained tRNAs. Peculiarly, in cichlids, the formation known as “T-arm” showed the lowest polymorphism levels among other structures in contrast to other organisms (e.g., scorpions). Comparing the whole family to the specific haplotilapiine lineage showed that the tryptophan tRNA was the most conserved tRNA, with signatures of possible purifying selection.The mitochondrial transfer RNA genes (tRNAs) attract more attention due to their highly dynamic and rapidly evolving nature. The current study aimed to detect and evaluate the dynamics, characteristic patterns, and variations of mitochondrial tRNAs. The study was conducted in two main parts: first, the published mitogenomic sequences of cichlids mt tRNAs have been filtered. Second, the filtered mitochondrial tRNA and additional new mitogenomes representing the most prevalent Egyptian tilapiine were compared and analyzed. Our results revealed that all 22 tRNAs of cichlids folded into a classical cloverleaf secondary structure with four domains, except for trnSGCU, missing the D domain in all cichlids. When consensus tRNAs were compared, most of the mutations were observed in the trnP at nucleotide levels (substitutions and indels), in contrast to trnLUAA. From a structural perspective, the anticodon loop and T-loop formations were the most conserved structures among all parts of the tRNA in contrast to the A-stem and D-loop formations. The trnW was the lowest polymorphic unneutral tRNA among all cichlids (both the family and the haplotilapiine lineage), in contrast with the neutral trnD that was extremely polymorphic among and within the haplotilapiine lineage species compared to other cichlids species. From a phylogenetic perspective, the trnC was extremely hypervariable and neutral tRNA in both haplotilapiine lineage and cichlids but was unable to report correct phylogenetic signal for the cichlids. In contrast to trnI and trnY, less variable neutral tRNAs that were able to cluster the haplotilapiine lineage and cichlids species as previously reported. By observing the DNA polymorphism in the coding DNA sequences (CDS), the highest affected amino acid by non-synonymous mutations was isoleucine and was equally mutated to valine and vice versa; no correlation between mutations in CDS and tRNAs was statistically found. The current study provides an insight into the mitochondrial tRNA evolution and its effect on the cichlid diversity and speciation model at the maternal level.

Combining sampling gear to optimally inventory species highlights the efficiency of eDNA metabarcoding

AbstractBiodiversity surveys may require the use of multiple types of sampling gear to maximize the efficiency of species detections, yet few studies have investigated how to optimally distribute effort among gear. In this study, we conducted eDNA metabarcoding and capture‐based sampling surveys (electrofishing, fyke netting, gillnetting, and seining) to sample fish species richness in a large northern temperate lake. We evaluated the success of the sampling methods individually and in combination to determine the allocation of effort and cost across sampling gear that provides the optimal approach for lake‐wide species inventories. We found that eDNA metabarcoding detected more species than any other sampling method, including 11 species that were not detected with any capture‐based approach. Optimal gear combination analyses revealed that detected species richness is maximized when most of the effort or budget is allocated to eDNA metabarcoding, with smaller allocations to seining and fyke netting. eDNA metabarcoding and capture sampling gear showed similar patterns of spatial heterogeneity in the fish community across habitat types, with pelagic samples forming a group that was distinct from nearshore samples. Our results indicate that eDNA metabarcoding is a rapid and cost‐efficient tool for biodiversity monitoring and that assessing the complementarity of multiple sampling types can inform the development of optimal approaches for measuring fish species richness.

Patterns of fish distribution in tropical rock pools at Príncipe Island, Gulf of Guinea

Little is known about the ichthyofauna from intertidal rock pools of the west coast of Africa, especially in the Gulf of Guinea. Rock pools are characteristic habitats of the intertidal zone of structurally complex rocky shores, adding important niche space to coastal fish species. In this study, rock pools of three similar rocky shores of Príncipe Island were sampled to describe the composition, abundance and distribution of fish assemblages and their relation to parameters of pool structure (volume, depth), water mass (temperature, salinity and pH) and biology (algal and coral cover, and biological species richness). A total of 18 fish species and one leptocephalus larva of unknown species, representing 13 families, were observed during sampling. In decreasing order, the five-most-abundant species were the goby Bathygobius burtoni, night sergeant Abudefduf taurus, West African rockhopper Entomacrodus cadenati, sailfin blenny Microlipophrys velifer and Biafra doctorfish Prionurus biafraensis, which together represented 81% of the total number of fish recorded during this study. The four-most-abundant species also proved to be the better adapted to the range of conditions found in rock pools. Overall, larger rock pools with minimal biological cover and higher salinity were found to support higher fish abundance and species richness. Most species individually preferred rock pools with larger volumes, but some presented a degree of habitat specificity, such as the absence or presence of biological cover. Species that were more-active swimmers preferred deeper pools.

Spatial patterns of reef fishes and corals in the thermally extreme waters of Qatar

The Persian Gulf is a thermally extreme environment in which reef corals have adapted to survive through temperature ranges that would be lethal to corals from other regions. Despite offering a unique opportunity to better understand how corals from other regions may adapt in the future, through a changing climate, much of the Gulf coral and fish communities remain to be described. In the southwestern Gulf nation of Qatar few reef sites have been described to date. We here characterize reef communities from 16 sites around the Qatar Peninsula, encompassing depths from 3 to 25m. We found the healthiest coral reef communities to be in deeper offshore reefs, with high coral and fish species richness and high coral abundance, likely a result of their occurrence below summer thermocline depths and distance from urban pressures. In contrast, we found shallow reefs, both nearshore and offshore, to have low species richness and abundance relative to deeper reefs, presumably due to impacts from recurrent bleaching events and development pressures over recent decades. The results of this work underscore the Qatar Peninsula as being at the biogeographic epicenter of the wider Gulf. However, further temperature increases may push both fishes and corals over their physiological limits. Management efforts at both the regional and global level are needed to reduce thermal stressors and preserve the rich reef ecosystems found in the waters surrounding Qatar.

Global water consumption impacts on riverine fish species richness in Life Cycle Assessment

Reduced river discharge and flow regulation are significant threats to freshwater biodiversity. An accurate representation of potential damage of water consumption on freshwater biodiversity is required to quantify and compare the environmental impacts of global value chains. The effect of discharge reduction on fish species richness was previously modeled in life cycle impact assessment, but models were limited by the restricted geographical scope of underlying species-discharge relationships and the small number of species data. Here, we propose a model based on a novel regionalized species-discharge relationship (SDR). Our SDR-based model covers 88 % of the global landmass (2320 river basins worldwide excluding deserts and permanently frozen areas) and is based on a global dataset of 11,450 riverine fish species, simulated river discharge, elevation, and climate zones. We performed 10-fold cross-validation to select the best set of predictors and validated the obtained SDRs based on observed discharge data. Our model performed better than previous SDRs employed in life cycle impact assessment (Kling-Gupta efficiency coefficient about 4 times larger). We provide both marginal and average models with their uncertainty ranges for assessing scenarios of small and large-scale water consumption, respectively, and include regional and global species loss. We conducted an illustrative case study to showcase the method's applicability and highlight the differences with the currently used approach. Our models are useful for supporting sustainable water consumption and riverine fish biodiversity conservation decisions. They enable a more specific, reliable, and complete impact assessment by differentiating impacts on regional riverine fish species richness and irreversible global losses, including up-to-date species data, and providing spatially explicit values with high geographical coverage.

An ecological assessment of Australia's first community oyster gardens

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

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

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

Spatio-temporal Variation of Shallow Microhabitats and Associated Juvenile Fish Assemblages in a Mediterranean Lagoon

Coastal lagoons are known to host numerous resident and migrant fish species. Spatio-temporal variation in abiotic and biotic conditions in these ecosystems results, however, in a mosaic of microhabitats that could differently affect juvenile growth and survival. To deepen our understanding of juvenile fish habitat requirements and their spatio-temporal use of lagoons, microhabitat characteristics and fish assemblages were monitored jointly in a small temperate lagoon (the Prévost lagoon), from March to October 2019. A total of 2206 juvenile fishes belonging to 22 species were collected. Resident lagoon species, especially Atherina boyeri, dominated the assemblage (74%), while, among migrant species, Sparus aurata (8%) and Liza aurata (5%) were the most represented. Changes in overall juvenile abundance were mainly temporal, following the seasonal shifts in water temperature, salinity, and chlorophyll a concentration (44.9% of the co-inertia). However, our results revealed that distinct types of microhabitats exist in small lagoons and that juvenile fish distribution among them is non-random. Indeed, fish species richness mainly differed among sampling sites in relation to their distance from the inlet and the complexity of the three-dimensional habitat structure (36.5% of the co-inertia). Juveniles preferentially selected microhabitats with medium to high structural complexity, which were essentially created by macroalgae. However, microhabitat preferences were both species and ontogenetic stage dependent, with more contrasting microhabitat requirements in young juveniles. These results underline the need for conservation measures to consider each lagoon as a dynamic mosaic of microhabitats with radically different importance for the juveniles of the various fish species that colonize them.

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

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

Diversity and distribution of fish in the Qilian Mountain Basin.

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

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

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

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

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

Influences of multiple anthropogenic disturbances coupled with a tailings dam rupture on spatiotemporal variation in fish assemblages of a tropical river

Abstract The Mariana disaster, resulting from the rupture of the Fundão tailings storage facility (TSF) in 2015, was a large‐scale environmental disaster that drastically affected the entire channel of the Rio Doce, southeastern Brazil. The disaster produced substantial channel siltation, increased turbidity, riparian damage and a massive fish kill. However, the Rio Doce basin has a long history of environmental degradation, including hydroelectric dams. The latter are major threats to the ichthyofauna because they affect flow regimes, trap sediments and large wood, select generalist species, impair fish migrations and favour non‐native invasive species. In this study, we analysed the effects of the rupture as well as impacts from the construction of a run‐of‐the‐river hydroelectric dam on native and non‐native fish abundances, and species richness and composition in the middle Rio Doce. To do this, we examined fish survey data collected before and after each disturbance upriver of the reservoir, in the reservoir area and downriver of the dam. The data were separated into three temporal intervals: free‐flowing river, post‐filling reservoir and post‐TSF disaster. To assess temporal changes in native and non‐native fish species richness, we used a rarefaction method and tested it with two‐way ANOVA, which also was used to compare fish abundances. To test temporal changes in fish assemblage composition we used a PERMANOVA test. We observed no significant differences in total native or non‐native species richness as a result of the dam or the disaster. However, we did observe increased non‐native individual abundances after the TSF rupture as well as native individual abundances, depending on the location studied. The assemblage composition also changed after dam construction and the TSF rupture, except for the upriver reach after dam construction. We conclude that both the dam and the TSF rupture affected fish assemblages, favouring increased non‐native abundances, and also changed fish assemblage composition. Our results suggest that a century of landscape and riverscape pressures had extirpated the sensitive fishes from the Rio Doce before the TSF rupture. We conclude that multiple long‐term chronic disturbances can be as harmful to aquatic biota as the acute effects of a major environmental disaster.

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

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

Selected freshwater fish species for assessing the water quality of the lower catchment of the Kelani River, Sri Lanka.

Kelani River is the most polluted river in Sri Lanka and the lower catchment is more polluted than the upper catchment. In the present study, freshwater fish species of the lower catchment of the river were investigated for the use of assessing the water quality. Cast net sampling and identification recorded 34 freshwater fish species from the lower catchment, the majority represented by family Cyprinidae. Fish species richness, diversity indices, distribution, abundance and the regression analysis of fish species with water quality parameters revealed high sensitivity and tolerance of three fish species with certain water quality parameters. Dawkinsia singhala was tolerant to the fluctuations of the chemical parameters of the water, while Rasbora daniconius and Pethia reval were tolerant to the physical parameters. Positive correlations were evident between the ammonium and phosphate concentrations of the water and distribution and abundance of D. singhala, while R. daniconius and P. reval showed positive correlations with turbidity of water and pH value respectively. Furthermore, the study reveals that D. singhala is more suitable for predicting the water quality of urban and peri-urban locations of the river, while P. reval and R. daniconius are more suitable for assessing the water quality of rural locations. Thus, the present study reveals a strong possibility of using D. singhala, R. daniconius and P. reval, as biological indicators for assessing the variation of water quality of the lower catchment of the Kelani River. However, despite the fact that such a study has been conducted for the first time in Sri Lanka, it is restrained by certain limitations, and seasonal variations of water quality parameters with fish parameters, adaptations inherent to fish species and food availability in different locations combined with long-term monitoring of fish assemblages have not been considered. Future studies investigating these aspects will further enhance the value of the study.

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.

Spatial Variation in the Composition and Diversity of Fishes Inhabiting an Artificial Water Supply Lake, Eastern China

With the intensification of eutrophication, many artificial water supply lakes that act as a biological filter for water diverted from rivers have been built to alleviate water scarcity in Eastern China. In this study, we selected Lake Yanlong, a representative artificial water supply lake in Yancheng City, as our experimental lake to explore how the community composition of fishes changed among different habitat types and assess potential consequences for effective water treatment. From October 2015 to October 2020, we conducted quarterly surveys of fish communities and environmental factors in the Mangshe River (MR; water for lake) compared to four different water treatment zones of Lake Yanlong (PZ, the pretreatment zone with inlet from the MR; EZ, the emergent macrophyte zone; SZ, the submerged macrophyte zone; DZ, the deep purification zone with outlet to urban waterworks). A total of 16,339 individual fish belonging to 11 families and 49 species were collected. Six of the eight dominant species observed across zones were small-bodied fishes. Despite reduced fish species richness, the relative abundance and biomass of fishes tended to be higher in Lake Yanlong relative to the MR. The Shannon-Wiener diversity index, Pielou evenness index, Simpson’s diversity index all decreased from the MR to the DZ in the following sequence: MR < PZ < EZ < SZ < DZ. Analysis of similarities and similarity percentage analysis confirmed that fish communities differed significantly among zones and Coilia ectenes, Carassius auratus, Pseudobrama simony, Hemiculter leucisculus, and Hemiculter bleekeri were the major differentiating species. Mantel’s test and redundancy analysis revealed that water depth, aquatic vegetation coverage, and phytoplankton concentrations were the major factors determining the spatial distribution of fishes when moving from the MR to the DZ of Lake Yanlong. Stocking piscivorous fish can be used as an effective measure to control the abundance of prolific small-bodied fishes in Lake Yanlong. The details backing these findings are important for understanding how the community composition of fishes among habitat types in Lake Yanlong influence water quality, and to develop suitable biomanipulation strategies for the management of fish resources and maintaining proper function of these artificial water supply lakes.

Ecological indices from environmental DNA to contrast coastal reefs under different anthropogenic pressures

AbstractHuman activities can degrade the quality of coral reefs and cause a decline in fish species richness and functional diversity and an erosion of the ecosystem services provided. Environmental DNA metabarcoding (eDNA) has been proposed as an alternative to Underwater Visual Census (UVC) to offer more rapid assessment of marine biodiversity to meet management demands for ecosystem health indices. Taxonomic information derived from sequenced eDNA can be combined with functional traits and phylogenetic positions to generate a variety of ecological indices describing ecosystem functioning. Here, we inventoried reef fish assemblages of two contrasting coastal areas of Curaçao, (i) near the island's capital city and (ii) in a remote area under more limited anthropogenic pressure. We sampled eDNA by filtering large volumes of seawater (2 × 30 L) along 2 km boat transects, which we coupled with species ecological properties related to habitat use, trophic level, and body size to investigate the difference in fish taxonomic composition, functional and phylogenetic indices recovered from eDNA metabarcoding between these two distinct coastal areas. Despite no marked difference in species richness, we found a higher phylogenetic diversity in proximity to the city, but a higher functional diversity on the more isolated reef. Composition differences between coastal areas were associated with different frequencies of reef fish families. Because of a partial reference database, eDNA only partly matched those detected with UVC, but eDNA surveys nevertheless provided rapid and robust species occurrence responses to contrasting environments. eDNA metabarcoding coupled with functional and phylogenetic diversity assessment can serve the management of coastal habitats under increasing threat from global changes.