Diversity Of Fish Communities Research Articles

Diversity of the ichthyofauna of the rivers of the southern macroslope of the Tarbagatai ridge (Alakol basin, Kazakhstan)

Freshwater ecosystems are among the most diverse ecosystem types. The fish communities of the rivers of the southern slope of the Tarbagatai ridge that flow into the system of the Alakol lakes (Alakol and Sasykkol) are currently poorly studied, with the exception of the Emel River. The analysis of literary sources up to the beginning of the 21st century is carried out and the results of our own research are presented. Catching and biological analysis of fish were carried out according to the standard method. The composition and biological parameters of mass fish species in the Karakol, Urzhar, Katynsu, and Emel rivers have been studied. Fish community diversity indices according to Simpson and Shannon were calculated. Using the PAST 4.07 statistical program, the species similarity (according to Sørensen) of the ichthyofauna of the studied rivers was analyzed. Analysis of the obtained results revealed a de-crease in the species diversity of fish in all the studied rivers, which numbered from 4 to 9 species. In general, the presence of 15 species of fish belonging to three families was found, while the basis of the list is representatives of the order carp. For 2 years of the study, it turned out that the composition of the ichthyofauna and the frequency of occurrence of fish species in the rivers were not stable. In addition to the Emel and Karakol rivers, the composition of the ichthyofauna consisted only of native species. The diversity of commercial acclimatized species and random invaders that were previously part of the ichthyofauna of the Karakol, Urzhar and Katynsu rivers has decreased.Key words: ichthyofauna, native, alien, fish communities, biodiversity.

Fish community diversity assessment of protected Saraiyaman wetland in the Ganga River basin, India

Fish community diversity assessment of protected Saraiyaman wetland in the Ganga River basin, India

Post‐filling phase ichthyofaunal community and fishery potential of Chitsuwa Reservoir, a small tropical reservoir in Zimbabwe

AbstractMany small reservoirs exist throughout Southern Africa, and with adequate management have the potential to contribute significantly to food security. The fisheries and limnology of the newly created Chitsuwa Reservoir in Zimbabwe were studied with the objective of generating information to support the development, management and sustainable use of fisheries to enhance the socio‐economic status of riparian communities. Based on gill nets of various mesh sizes, it was confirmed that the reservoir is presently inhabited by a fairly diverse fish community comprising ten species belonging to five families (Clarias gariepinus; Coptodon rendalli; Labeo cylindricus; Marcusenius macrolepidotus; Micropterus salmoides; Momyrus longirostris; Oreochromis mossambicus; Oreochromis niloticus; Serranochromis microcephalus; and Tilapia sparrmanii). Oreochromis niloticus dominated the reservoir with respect to both abundance, biomass and catch. The index of relative importance revealed O. niloticus and M. macrolepidotus were the most important species. Results from the Canonical Correspondence Analysis revealed a clear division of the fish species that followed the environmental variables. Although fisheries may benefit from the invasive M. salmoides and the established O. niloticus, their presence in the reservoir is a cause for concern for conserving native congeneric species that risk extirpation through documented mechanisms. The results of the present study suggest sound management of the reservoir is required to raise its potential of supporting the livelihoods of the surrounding communities with a predicted annual fish yield of 61.5 t/year. Management of this reservoir should involve the local communities, empowering them so that they practice sustainable non‐destructive fishing methods.

江西柘林水库鱼类群落结构及功能多样性分析

PDF HTML阅读 XML下载 导出引用 引用提醒 江西柘林水库鱼类群落结构及功能多样性分析 DOI: 10.5846/stxb202106031466 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2019YFD0900603）；财政部和农业农村部：国家现代农业产业技术体系资助（CARS-46）；中国水产科学研究院基本科研业务费院级湖库增殖渔业创新团队项目（2020TD57） Community structure and functional diversity of fishes in Zhelin Reservoir, Jiangxi Province Author: Affiliation: Fund Project: National Key Research and Development Program of China (No.No.2019YFD0900603); Supported by China Agriculture Research System of MOF and MARA（CARS-46）; Central Public-interest Scientific Institution Basal Research Fund，CAFS (NO.2020TD57) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了解江西柘林水库鱼类群落结构和多样性的时空变化特征，研究鱼类物种多样性和功能多样性的关系，于2020年9月至2021年4月在该水库调查分析了鱼类物种组成、优势度及群落物种多样性和功能多样性。结果表明，共采集鱼类53种，分属于5目12科36属。其中，鲤形目（38种）种类最多，占调查物种数的71.69%，柘林水库上、中、下游库区分别采集到鱼类36、40和32种，各库区均以鲤形目鱼类为主，分别占采集物种数的72.97%、85.00%和75.00%。优势物种主要是䱗（Hemiculter leucisculus）、鳙（Aristichthys nobilis）和黄尾鲴（Xenocypris davidi），重要种主要是草鱼（Ctenopharyngodon idella）、鲢（Hypophthalmichthys molitrix）、鳊（Parabramis pekinensis）、鲫（Carassius auratus）、蒙古红鲌（Erythroculter mongolicus）等。鱼类群落结构季节性差异大于空间格局差异，主要表现为秋季和冬季之间；生物多样性指数Margalef和功能丰富度指数在上游修河水域相对较高，鱼类物种多样性和功能多样性空间格局差异性大于时间尺度下的差异性。物种多样性与功能多样性的回归分析结果显示，功能丰富度与物种多样性指数之间存在显著的正相关关系；功能冗余度与各物种多样性之间呈现负相关关系，说明物种数的增加导致了库区鱼类功能丰富度的增加和功能冗余度的降低，而功能均匀度未发生明显的变化，主要原因为调查区域内拥有不同功能性状的鱼类群体之间在个体数比例上呈现不均匀分布的模式，这一结果预示着拥有较多物种的群落生态位重叠度相对较低，生态系统受干扰后的恢复能力较差。总体而言，保护鱼类生物多样性和维护生态系统的稳定性应该通过调控鱼类种群结构达到提高鱼类群落冗余度以及资源和生境可用性的目的。 Abstract:To understand the spatial and temporal variation of fish assemblage structure and biodiversity, as well the relationships between fish taxonomical diversity and functional diversity, species compositions, the dominant species, taxonomical and functional diversity of fish communities which were captured from Zhelin Reservoir from September 2020 to April 2021 were investigated and analyzed. The results showed that a total of 53 fish species belonging to 5 orders, 12 families, and 36 genera were sampled with dominant Cyprinidae accounting for 71.69% of the total species. Among the reservoir spatial scales, 36, 40 and 32 fish species which accounting for 72.97%, 85.00% and 75.00% of the total sampled species were captured from upper-, middle- and low-reach, respectively. Hemiculter leucisculus, Aristichthys Nobilis and Xenocypris davidi were dominant species, while Ctenopharyngodon idella, Hypophthalmichthys molitrix, Parabramis pekinensis, Carassius auratus and Erythroculter mongolicus were main species in Zhelin Reservoir. The analysis of PERMANOVA (Permutational Multivariate Analysis of Variance) using the fish assemblage matrixes showed that the seasonal variation of species compositions was more significant than the spatial scale, and the variations were mainly performed between two seasons of antum and summer. Meanwhile, biodiversity indexes and functional diversity indexes of fish assembalges performed relative higher variations among spatial scales than temporal scales. Margalef index were relatively higher in the Xiuhe River than those in other water sites, while the indexes of Shannon, Simpson and Peilou indexes showed no variation among the reaches. Functional richness possessed relative higher level in upper reach than midlle and lower reaches, while functional evenness and functional disperse performed non changes among spatial scales. Functional redundancy had no variation among spatial and temporal scales. Regression analyses showed significant positive relationships between the biodiversity index of functional richenss and functional disperse with each taxonomical diversity index, while there were negative relationships between functional redundancy and taxonomical diversity indexes, which implying the increase of species richness led to the increase of the functional richness and decrease of functional redundancy. However, functional evenness did not change obviously which can mainly be explained by the disproportionate individuals of different fish functional groups. The results implied that interference resulted in a lower niche overlap of fish community with high species richness and lower ecosystem recovery ability. In general, the species diversity level of Zhelin Reservoir is lower and the anti-interference ability of this ecosystem is relatively weaker. To protect fish biodiversity and maintain the stability of the ecosystem, it is necessary to improve the fish community redundancy and the availability of resources and habitats by regulating the fish population structure. 参考文献 相似文献 引证文献

Reef fish community structure along the southeastern US Atlantic continental shelf break and upper slope appears resistant to increasing lionfish (Pterois volitans/miles) density

Temperate reefs host diverse fish communities along the southeast United States Atlantic coast (SEUS), yet the sustainable management of reef fishes faces myriad challenges. One challenge has been the introduction of Indo-Pacific lionfish (Pterois volitans/miles; hereafter "lionfish"), which have spread quickly throughout the SEUS since their introduction in the late 1900s. We analyzed long- term (2001–2019) video data along the continental shelf break and upper slope (45–125 m deep) of the SEUS to assess changes in lionfish densities over time, characterize reef fish community structure, and determine if native reef fish community structure has changed due to lionfish. Lionfish densities increased substantially during the study, from zero individuals observed in 2001 to approximately 1.2 individuals observed per 100 m 3 (and present in all included transects) by 2019, yet no fish community metrics were negatively related to lionfish density. Demersal habitat influenced fish community structure more than any other variable examined, with more individuals and different fish communities occurring on high-relief compared to low-relief hardbottom habitats. The effects of latitude, depth, and bottom temperature on reef fish community structure were generally weak or nonexistent. Although previous empirical work has found that lionfish negatively affect native fishes at small scales (<30 km2), it is unclear why we did not find similar results in our larger- scale study. It may be related to vagaries of the spatial scale of observation, lionfish effects being primarily limited to high- relief habitats, time lags, or lionfish densities not being high enough yet to cause observable ecological effects.

A multi-tiered assessment of fish community responses to habitat restoration in a coastal lagoon

Essential fish habitat is critical for foraging, breeding, or as refugia. As such, restoration of these habitats has the potential to increase the diversity and abundance of fishes. Here, we explored how fish communities responded in the first 12-24 mo following oyster reef restoration. Study sites included 8 restored reefs plus 4 live and 4 dead reefs as controls. Oyster reef metrics (e.g. density, height, thickness) and fish abundance and diversity metrics were quantified, including species richness, Shannon diversity, Simpson’s diversity, and Pielou’s evenness. Species composition was explored further to identify indicator species and assess habitat preferences. Patterns of fish community diversity and species composition were compared to oyster reef metrics to discern what oyster reef characteristics best predict fish diversity. Results showed that intertidal oyster reefs were structurally restored and shifted from resembling negative control reefs to positive control reefs within 12-24 mo. Across all treatment types, oyster shell height and reef thickness were the best predictors of fish diversity. However, at the fish community level, assemblages at restored reefs were similar to those at positive and negative controls. Species-level analyses suggest treatment types have unique indicator species, including Chilomycterus schoepfi (striped burrfish) for dead reefs, Lutjanus synagris (lane snapper) for restored reefs, and Gobiosoma robustum (code goby) for live reefs. This work suggests fishes can be used as higher trophic level indicators of restoration success, and ecosystem-based approaches, such as habitat restoration, can restore essential fish habitat, thus benefiting fish communities while moving coastal ecosystems toward sustainability.

Resource use among top‐level piscivores in a temperate reservoir: implications for a threatened coldwater specialist

AbstractEvaluations of resource use among native piscivores in natural lakes have consistently documented significant partitioning that supports coexistence. Partitioning may be less prominent in reservoirs where water‐level fluctuations can compress habitat and trophic diversity, but studies are lacking. Stable isotopes and bioenergetic models were used to quantify trophic interactions within a native piscivore assemblage inhabiting a temperate irrigation reservoir and explore implications for coexistence with a focus on threatened bull trout (Salvelinus confluentus). As hypothesised, adult bull trout exhibited the greatest degree of trophic specialisation by consuming mostly coldwater pelagic forage fish, which were consumed seasonally by the more abundant burbot (Lota lota) and northern pikeminnow (Ptychocheilus oregonensis). Numerous trophic niche overlap probabilities exceeded 70%, were as high as 93% and greatest between bull trout and burbot. Bioenergetics simulations demonstrated the high seasonal consumption capacity of burbot relative to northern pikeminnow. As a result, threefold to fourfold fewer burbot were required to consume the annual productivity of coldwater prey important for bull trout, particularly in the absence of small‐bodied mesothermic or eurythermal fish as a buffer. Collectively, our analysis elucidated relatively strong trophic niche overlap among similarly sized piscivores, the importance of maintaining a diverse forage fish community for promoting coexistence and the greatest potential for competitive interactions between adult bull trout and burbot if key prey were limited or less diverse. More studies in regulated systems are needed to test for consistent patterns and identify mechanisms that limit or promote coexistence amid growing human‐induced environmental change and demands on freshwater.

Sport fish home range responses to a littoral coarse woody habitat addition in a north‐temperate lake

AbstractBehavioural responses of fishes to littoral zone habitat enhancements are relatively understudied in diverse fish communities but are critical for understanding overall fish community responses. To advance knowledge on effects of coarse woody habitat (CWH) littoral zone enhancements, we initiated a long‐term study on Sanford Lake, Vilas County, Wisconsin, where 160 trees were added to the littoral zone of the lake in 2018. We tested for short‐term home range responses in muskellunge (Esox masquinongy), smallmouth bass (Micropterus dolomieu) and walleye (Sander vitreus) to this CWH addition. We used radio telemetry data collected premanipulation (2017) and postmanipulation (2018 and 2019) to construct annual home range estimates for each species. Limited kernel density (LKD) estimates, which partially exclude terrestrial areas, were used for estimating 50% and 95% home ranges. Over the course of the three years, average home ranges for each study species increased suggesting a behavioural response to the CWH addition. Muskellunge had the greatest home range estimate increase, followed by smallmouth bass and then walleye. Muskellunge and smallmouth bass had similar home ranges, which were larger than walleye home ranges. Increased home ranges across species could be a searching or deviation from premanipulation equilibrium home range response as a result of the CWH serving as a prey fish refuge, which may make them relatively inaccessible to predators. Our results suggest that fish behavioural responses to CWH additions may be species‐specific and should be taken into consideration prior to implementing littoral habitat enhancements in diverse fish communities.

Hydrologic connectivity and land cover affect floodplain lake water quality, fish abundance, and fish diversity in floodplain lakes of the Wabash‐White River basin

AbstractFloodplain lakes are important aquatic resources for supporting ecosystem services, such as organismal habitat, biodiversity, and the retention of nutrients and sediment. Due to geomorphic alteration of river channels and land‐cover change, degradation to floodplain lakes in the Ohio River basin is occurring at a rate that will escalate as climate change causes increased flood intensity and the seasonal redistribution of rainfall. A better understanding of the local drivers that affect oxbow lakes is needed for targeted floodplain restoration efforts designed to slow degradation. We examined the effects of land cover, topography, and hydrologic connectivity on water quality and fish diversity and abundance in nine floodplain lakes with potentially high remnant ecological function in the Wabash‐White watershed (Indiana, Ohio, and Illinois). Data collection included water‐quality parameters; stable water isotopes; total phosphorus, total nitrogen, and chlorophyll‐a; and fish community diversity and abundance. Results indicate that hay/pasture land cover and decreased topographic relief in the local oxbow watersheds, along with reduced river hydrologic connectivity, were related to an increase in total phosphorus, total nitrogen, and chlorophyll‐a. Greater biodiversity and abundance in fish assemblages were evident in oxbow lakes that were more disconnected from the main channel. The results of this study suggest that hydrologic connectivity of oxbow lakes with the contributing drainage area and the main channel influence nutrients and fish communities. Knowing the influencing factors can help ecosystem managers better protect these valuable floodplain lake ecosystems and prioritize restoration efforts amidst increasing stressors due to climate and land‐use changes.

Correction to: Fish composition, but not richness or abundance, differ among Phragmites, Typha, and Schoenoplectus zones during a high-water year

Phragmites australis (ssp australis) is an aggressive colony-forming species that displaces emergent vegetation in North America, including native bulrushes (Schoenoplectus sp.) and both native and invasive cattails (Typha sp.). Phragmites expansion can alter habitat and negatively affect reptiles, amphibians, and birds; less is known about Phragmites’ utility as fish habitat and its impact on fish communities in freshwater coastal wetlands. To assess fish use of Phragmites in summer, we compared habitat characteristics, water quality, and fish community composition, diversity, and abundance among stands of flooded Phragmites, Typha, and Schoenoplectus at 16 sites across four regions of the Laurentian Great Lakes. Despite marked differences in water quality (higher pH and morning dissolved oxygen in Schoenoplectus) and habitat characteristics (higher stem density in Phragmites), there were no significant differences in fish species richness or catch per unit effort among vegetation types; there was a distinct fish assemblage in Schoenoplectus (more Cyprinids) compared to both Phragmites and Typha (more Centrarchids). This suggests that expansion of Phragmites or Typha at the expense of Schoenoplectus may alter wetland fish assemblages; however, with no clear differences in other fish community metrics, flooded Phragmites may provide habitat for some fishes during the summer, in the study wetlands.

Movement Ecology of a Potamodromous Top Predator in a Large Lake: Synchrony and Coexistence of Distinct Migratory Patterns

AbstractMigrations are a critical component of the life histories of many highly mobile animals. Potamodromous migrations that occur within large lakes are poorly understood for most species. This lack of understanding hampers restoration efforts and adaptive management because the movement of species and underlying patterns and mechanisms help scientists identify important habitats and quantify species’ roles in the ecosystem. This study quantified the spatiotemporal movements and migratory patterns of Lake Trout Salvelinus namaycush, an iteroparous, potamodromous predator, in eastern Lake Ontario. The lake is highly managed and supports a diverse fish community of native and nonnative species. The movements of 41 Lake Trout were quantified over 2.4 years (December 2016 to April 2019) across a large array of 196 acoustic receivers in eastern Lake Ontario. An analysis of individual movements revealed a potential annual convergence occurring in the fall at a location other than the spawning grounds, followed by a synchronized migration to spawning areas. Consistent with divergent migrations, return migration was asynchronous among individuals but consistent in timing interannually, stretching over a longer period than did prespawning movements and across multiple routes. The data suggest the existence of three groups (i.e., contingents) of Lake Trout with distinct migratory behaviors. This study provides important information on the migratory patterns and routes and a potential staging area for a potamodromous top predator population in a large lake. This information can help managers understand the potential success and implications of employing different rehabilitation strategies, such as diversifying populations of Lake Trout through selective strain stocking in large deep lakes to aid reestablishment across habitats. In addition, our results have the potential to improve community dynamics modeling, understanding of nutrient cycling, and overall ecosystem function of large lakes.

A new composite abundance metric detects stream fish declines and community homogenization during six decades of invasions

AbstractAimWe developed a new technique, utilizing species‐specific counts of individuals from historical fish community samples, to examine landscape‐level, spatio‐temporal trends in relative abundance distributions. Abundance‐based historical distribution analyses are often plagued by data comparability issues, but provide critical information about community composition trends inaccessible to those using analyses based only on species presence–absence. We established trends in native and non‐native fish abundance and community homogenization, uniqueness and diversity to help local conservation managers prioritize targets and motivate similar studies globally to support fish conservation.LocationUpper and middle New River (UMNR) basin, Appalachian Mountains, USA.MethodsWe compiled catch data from 61 years of fish community surveys (1958–2019) and tested for community homogenization by comparing data from repeatedly sampled sites (1900s versus 2000s samples) using dispersion analyses. We measured community uniqueness (site contributions to beta diversity) and species diversity (Shannon index) at sampled streams to identify potential conservation hotspots. We then used regression analyses and Wilcoxon signed‐rank tests to examine species‐specific basin‐wide and local abundance trends and identify species of potential conservation concern.ResultsDispersion of sites in species abundance space was significantly greater in the 1900s compared with the 2000s, indicating homogenization had occurred. Of 36 native species analysed, 44.4% (16) showed basin‐wide declines. Non‐native species exhibited mixed patterns; site‐level abundance increased in 2 of 15 species analysed (13%).Main conclusionsOur results indicate basin‐wide community homogenization has occurred within the UMNR, but many unique and diverse communities persist. If conserved, these could help maintain regional fish diversity. We found basin‐wide declines in four endemic species, as well as spread patterns of non‐native and native species that were not detected by a presence–absence analysis applied within the same study area. This finding illustrates the importance of considering both species’ abundance and occurrence patterns as separate dimensions of biodiversity to inform conservation planning.

Middle Pleistocene fauna and palaeoenvironment in the south of Eastern Europe: A case study of the Medzhybizh 1 locality (MIS 11, Ukraine)

The Middle Pleistocene was a period of dynamic changes in Europe. During MIS 11, a number of modern mammal taxa appeared and environmental conditions remained warm and favourable for a relatively long time. The Medzhybizh 1 locality of Ukraine dated to this very period comprises alluvial deposits with rich animal remains, which allow not only to reconstruct the fauna composition, but also to highlight the environmental conditions that dominated at this locality. A revision of the fauna of Medzhybizh 1 locality based on remains of all vertebrate groups revealed a taxonomically diverse fish community (16 species of 11 genera) dominated by cyprinids common for lacustrine or riverine assemblages. Amphibians are represented by 11 species, while the number of reptile and bird remains are less significant. Mammals are the most represented group at the locality, including small mammals (30 species), carnivorans (2 species), and ungulates (5 taxa), the latter dominated by C. elaphus. The taxonomic composition of terrestrial groups indicates temperate climate with boreal-type forests and meadows similar to cold steppe, as well as low wet areas and riparian habitats inhabited by amphibians, reptiles, insectivores, beavers, and various voles. The fish assemblage indicates a partially overgrown but well-aerated water body (lake or slow-flowing river) with sandy-silty bottom. Lithic artefacts found at the Medzhybizh 1 locality contribute to a better understanding of relationships between ancient hominins and faunas during the Middle Pleistocene of Eastern Europe.

Natural distinction of carbon and nitrogen isotopic niches in common fish species across marine biotopes in the Yellow River estuary.

Stable isotope analysis is a universally recognized and efficient method of indicating trophic relationships that is widely applied in research. However, variation in stable isotope ratios may lead to inaccuracies due to the effects of complex environmental conditions. This research compared the carbon and nitrogen isotopic niches of fish communities between diverse biotopes around the Yellow River estuary and adjacent sea areas, with the aim of revealing distinctions in stable isotopic niche metrics, trophic positions, and feeding preferences. Our analysis of the food source contribution indicated that allochthonous sources were considered major energy sources in estuarine areas directly affected by Yellow River‐diluted water, while autochthonous benthic and pelagic producers dominated carbon input into the food web in Laizhou Bay and the open water. A significant variation in the fish δ15N characteristic was found within estuarine adjacent regions, so, together with the results from previous studies, we deemed the local high concentration of dissolved inorganic nitrogen as the original trigger of the abnormal δ15N characteristic in fishes via a transport process along food chains. These results provide a new perspective on the natural distinction of carbon and nitrogen isotopic niches. The detailed data reported here enhance our understanding of variations in fish communities in estuarine ecosystems.

EDNA metabarcoding in lakes to quantify influences of landscape features and human activity on aquatic invasive species prevalence and fish community diversity

AbstractAimOur goal was to use eDNA metabarcoding to characterize fish community diversity, detect aquatic invasive species (AIS) and assess how measures of community (or AIS) diversity are influenced by lake physical and environmental covariates, measures of hydrological connectivity and human accessibility.LocationMichigan, USA.MethodseDNA samples collected from 22 lakes were sequenced using two mitochondrial gene regions (12S and 16S rRNA). Metabarcoding data were compared to traditional fisheries survey data for a subset of lakes, and data from all 22 lakes were combined with environmental information to identify significant associations with community diversity and AIS relative abundance.ResultsOccupancy modelling indicated that detection probabilities were generally higher with eDNA than traditional fisheries gear. Measures of connectivity with upstream aquatic habitats were positively associated with both AIS relative abundance and fish species diversity. We also demonstrate the use of spatial interpolation methods to map distributions of species diversity and AIS relative abundance within lakes.Main conclusionseDNA metabarcoding methods provided information on the composition and diversity of fish assemblages and the presence of AIS in freshwater lakes that varied greatly in drainage connectivity and anthropogenic development. Our case study identified associations between environmental covariates and fish diversity or AIS relative abundance across lakes. This information is of particular importance given increasing anthropogenic disturbance, invasive species spread and associated declines in aquatic biodiversity. Incorporating eDNA metabarcoding as a supplement to traditional fisheries surveys will permit managers to identify greater numbers of taxa, including early detection of AIS, with less field effort and fish mortality. Further, eDNA methods may more accurately identify physical and biological features that correlate with diversity and abundance and allow agencies to more effectively direct AIS management activities.

Comparison of regression-based and machine learning techniques to explain alpha diversity of fish communities in streams of central and eastern India

Over the past several decades, ecologists have been striving to develop models that accurately describe species-habitat relationships across ecological communities. Statistical models that explain ecological dynamics need to consider the nuances of the complex interactions between communities and ecological factors. Here, we used multiple linear mixed models (LMM), generalized additive models (GAM), multivariate adaptive regression splines (MARS), and artificial neural networks (ANN) to model species richness and diversity of freshwater fishes in eastern and central India. The models were based on fish abundance and associated ecological data over three years across the study regions. We developed global models using all predictors after removing highly correlated variables (Pearson’s r > 0.7). Results revealed conductivity, water temperature, and water velocity as the most important predictive factors of both species richness and diversity. We, then, built two subsets of selected factors to build predictive models for diversity and richness- one variable set containing common significant factors as revealed from the four different modeling methods used and the second, using an automatic feature selection technique. Amongst the modeling methods used in our study, ANN was found to create the best fit models for explaining nonlinearities between response variables and predictors. The importance of variable selection is highlighted, given that subset 1 (common consensual factors) creates more homogeneity in predictions compared to using subset 2 (automated feature selection). Contrary to similar studies in recent years, which show machine learning (ML) methods to typically outperform conventional methods, our results revealed that ANN performed at par with other methods in terms of predictive power. Our findings underline the need for a judicious choice of modeling techniques based on the availability of the data and the ecological communities being studied.

Editorial: Green or red: Challenges for fish and freshwater biodiversity conservation related to hydropower

Editorial: Green or red: Challenges for fish and freshwater biodiversity conservation related to hydropower

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.

Diverse marine fish assemblages inhabited the paleotropics during the Paleocene-Eocene thermal maximum

The Paleocene-Eocene thermal maximum (PETM) was a short interval (120–220 k.y.) of elevated global temperatures, but it is important for understanding biotic responses to climatic warming. Consequences of the PETM for marine fishes remain unclear, despite evidence that they might have been particularly vulnerable to increasing temperatures. Part of this uncertainty reflects a lack of data on marine fishes across a range of latitudes at the time. We report a new paleotropical (~12°N paleolatitude) fish fauna from the Dababiya Quarry Member of Egypt dating to the PETM. This assemblage—Ras Gharib A—is a snapshot of a time when tropical sea-surface temperatures approached limits lethal for many modern fishes. Despite extreme conditions, the Ras Gharib A fauna is compositionally similar to well-known, midlatitude Lagerstätten from the PETM or later in the Eocene. The Ras Gharib A fauna shows that diverse fish communities thrived in the paleotropics during the PETM, that these assemblages shared elements with coeval assemblages at higher latitudes, and that some taxa had broad latitudinal ranges substantially exceeding those found during cooler intervals.

How functionally diverse are fish in the deep? A comparison of fish communities in deep and shallow‐water systems

AbstractAimFunctional diversity metrics inform how species’ traits relate to ecosystem functions, useful for quantifying how exploitation and disturbance impact ecosystems. We compare the functional diversity of entire fish communities in a shallow‐water region with a deep‐sea region for further insight into the differences between these ecosystem types.LocationThe regions compared in this study were selected to represent a shallow‐water coastal region, Tasman and Golden Bays (TBGB), and a deep‐sea region, Chatham Rise (CR), in New Zealand.MethodsFunctional diversity was assessed using four metrics: functional richness, evenness, divergence and dispersion. We compared these metrics across four key functions: habitat use, feeding, locomotion and life history.ResultsOur results showed that overall, the shallow‐water and deep‐sea ecosystems had equal diversity. When focusing on the four ecological functions, the two ecosystems exhibited equal diversity metrics across most analyses. Of the significantly different results, the deep‐sea had higher functional richness for habitat use and locomotion traits, lower functional dispersion for feeding and lower functional evenness for life history.Main conclusionsDifferences across the functions highlight higher diversity of habitat utilization by deep‐sea fish, while lower diversity in feeding suggests deep‐sea fish tend towards generalist diets, likely driven by low food availability. Deep‐sea fish displayed an increased range of locomotive traits in our analyses, but this conflicts with existing evidence and warrants further study. Life‐history results suggest deep‐sea fish exhibit higher clustering of traits, indicating potential under‐utilization of life‐history strategies in the deep‐sea. Our results demonstrate that although deep‐sea fish communities have similar levels of diversity to shallow‐water communities, the traits that structure this diversity differ, and therefore, the systems may respond to exploitation differently.