Diversity Of Fish Communities Research Articles

Environmental DNA as a novel tool for monitoring fish community structure and diversity feature in the northern Antarctic Peninsula

The northern Antarctic Peninsula (NAP), one of the fastest warming area around the Southern Ocean, hosts a large variety of endemic fish and is influenced by complex hydrography. However, the dynamics of fish diversity kept unclear and without monitoring. Monitoring of environmental DNA (eDNA) is a noninvasive, ecofriendly, and accurate approach for detecting aquatic organisms, including fish. In this study, the fish composition and diversity were detected by high-throughput sequencing of eDNA for the first time in the NAP. Overall, 32 species (1 order, 6 families, and 25 genera) of fishes were detected in the environmental water samples from 18 stations around the NAP, in which number of fish species were similar in the Drake Passage and the northern shelf of the South Shetland Islands (DP-SSIs) and the Bransfield Strait (BS). Most of the fish species were identified in previous Antarctic fish surveys using conventional methods, which supports the applicability of eDNA-based survey. Moreover, Pogonophryne albipinna was detected firstly in the NAP. Among the identified fish species, Champsocephalus gunnari and Notothenia rossii had the highest abundance (45.04% and 27.59%, respectively). There was difference in fish composition between the DP-SSIs and BS stations, although alpha diversity indices did not differ. The dissolved oxygen content and water temperature were the main drivers for the differences in fish species composition between areas. Our results indicated that eDNA could be a rapid and accurate biomonitoring approach for the entire Southern Ocean, particularly in areas with difficult logistics, in the future.

Contrasting pollution responses of native and non-native fish communities in anthropogenically disturbed estuaries unveiled by eDNA metabarcoding

Understanding the influence of environmental pollutants on the assembly mechanisms of estuarine fish communities is vital for addressing conservation challenges in these biodiverse ecosystems. Although significant research has explored the toxic impacts of pollutants such as petroleum, heavy metals, and eutrophication on individual species and populations, their effects on community assembly processes and the differential responses of native versus non-native fish at the meta-community level remain inadequately understood. This study utilized environmental DNA (eDNA) metabarcoding to analyze fish community diversity across 28 subtropical estuaries in China, assessing how these pollutants affect community composition and assembly mechanisms. Results indicated that eDNA was 2.54 times more effective than traditional methods in species identification, while also enabling the detection of a higher number of non-native fish species and more diverse functional guilds within estuarine ecosystems. A significant distance decay pattern (p < 0.05) was observed among native fish, whereas non-native species exhibited non-significant patterns. Neutral and null models showed that non-native species had significantly higher migration rates (0.005939 vs 0.001757) and a greater contribution of stochastic processes (82.38% vs 70.59%) compared to native species. Additionally, distance-based redundancy analysis (db-RDA), variance partitioning analysis (VPA), and correlation analyses revealed that native species were strongly constrained by environmental factors, particularly oil, Hg, Zn, Pb, Cr6+, and NH4+, while non-native species displayed notable resilience to these pollutants. These findings highlight the potential for non-native species to disproportionately influence community dynamics and assembly through unrestricted random dispersal amid environmental disturbances. This research clarifies the contrasting ecological responses of native and non-native fish communities to anthropogenic pressures in estuarine environments, offering essential insights into ecosystem resilience and informing biodiversity conservation strategies in rapidly changing coastal ecosystems.

A fish community comparison upstream and downstream a high-head dam on the Upper Mississippi River

Abstract Standardized sampling is useful for detecting and monitoring variations in fish communities and the establishment and spread of invasive species. Lock and Dam 19, a high-head dam with a 10- meter hydraulic head, creates the largest impoundment on the Upper Mississippi River. Upstream, Pool 19 is characterized by static water levels and expansive macrophyte beds. Downstream, Pool 20 is characterized by lotic conditions and sparse vegetation. Lock and Dam 19 serves as barrier to upstream migration of fishes, particularly Bigheaded carp (Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molotrix). There is limited standardized fisheries data available for Pools 19 and 20, particularly in off-channel areas. In 2013 and 2014, we conducted two years of standardized electrofishing in Pools 19 and 20 to 1) detect a presence of adult or juvenile Bigheaded carp, 2) quantify differences in fish community structure (i.e., relative abundance of species) between Pools 19 and 20 and among strata (i.e., backwater, side channel, main channel, and impounded reaches), and 3) quantify hydrological differences (i.e., water quality variables) between Pools 19 and 20 and among strata. We detected two Bigheaded carp upstream Lock and Dam 19, the first to be documented using a standardized collection method. We used permutational multivariate analysis of variance using distance matrices (veganR package version 2.6-4) to determine that fish community structure differed significantly between pools (P&amp;lt; 0.01) and among strata (P&amp;lt; 0.01), except between main and side channel borders. We determined water quality variables differed significantly between the pools and among strata demonstrating strata proportional differences may drive the fish community differences between Pools 19 and 20. We have demonstrated that expanding standardized sampling efforts to Pools 19 and 20 is important to understand long-term changes in fish assemblages and the effects of Lock and Dam 19 on the ecology of the Upper Mississippi River.

Fishing for more than shellfish: a systematic review of fish community monitoring of shellfish reefs

Shellfish reefs, characterized by habitat‐forming bivalves, are increasingly recognized as globally significant coastal ecosystems and valuable fish habitats. Shellfish reefs provide structural refugia, foraging grounds, and nurseries for diverse fish communities, including species with socioeconomic value. However, efforts to quantify the value of shellfish reefs as fish habitats are challenged by the limited and fragmented knowledge of published monitoring practices. Here, we systematically assess 116 peer‐reviewed studies to provide a global overview of literature evaluating fishes in these ecosystems. Research was unevenly distributed, with 67% of the studies concentrated in the United States, 61% on restored reefs, and 83% focused on oyster reefs. Few studies have directly compared fish communities between natural versus restored, or intertidal versus subtidal shellfish reefs. Methods to quantify fishes varied based on research objectives, tidal zonation, and targeted subsets of the fish assemblages. Gill nets, substrate trays, and underwater video stations were the most common methods, with 44% of studies deploying more than two methods to survey fish communities. Differences in the monitoring methods, research designs, and variables reported were also synthesized and discussed. From this review, we identified knowledge gaps and monitoring trends in fish community assessments that can guide future shellfish reef research and conservation efforts.

Chatting behind the reef: Fish bioacoustic diversity of tropical back-reefs in Fiji, South Pacific

Back-reef habitats are important and fragile transition zones acting as nurseries for many coral reef fishes. In this framework, Passive Acoustic Monitoring (PAM) can be an important tool to evaluate the diversity and dynamics of sonic fish community. Here, we investigated the diversity, spatial and diel dynamics of fish sounds in back-reef habitats at Makogai Island in Fiji, South Pacific. Synchronized underwater recorders were deployed in 4 bays collecting data for about 4 days. The abundance of 12 different sub-categories of fish sounds were quantified. Signals were acoustically characterized and the level of discrimination between the sub-categories was evaluated by Discrimination Function Analysis. Generalized Additive Models showed that the abundance of signals was related to the bay and the hour. Moreover, the Shannon Diversity and Equitability Indices were calculated using acoustic and visual census data to describe fish biodiversity of each bay. The two bays with greater biodiversity based on visual census also showed a greater acoustic diversity at dawn and night. Our results highlight the importance of PAM to reveal the diversity of fish community in back-reef habitats, providing a baseline to understand future changes in these crucial environments.

New Insights into Fish Diversity in the Yellow and Bohai Seas Based on Environmental DNA Technology

Marine biodiversity is increasingly threatened by overfishing and marine pollution. A comprehensive understanding of the biodiversity in the Yellow and Bohai Seas is essential for resource conservation. This study conducted a large-scale survey of fishery resources in the Yellow and Bohai Seas to investigate fish community structure and diversity using eDNA technology. The results showed that 57 and 65 fish species were recorded in spring and summer, respectively, with 46 species identified in both seasons. A total of nine dominant species were identified in spring, mainly belonging to Perciformes, while seven dominant species were identified in summer, primarily from Clupeiformes. In different regions, no significant differences in fish α diversity were observed between spring and summer. However, significant seasonal differences were found in both α and β diversity. At the spatial level, fish species in the Yellow and Bohai Seas occupied similar ecological niches. However, at the temporal level, there are certain differences in the ecological niches of fish communities between seasons. Phylogenetic diversity showed no significant differences at the spatial scale, yet notable seasonal variations were observed at the temporal scale, with spring (661.46) significantly exceeding summer (540.30). The Mantel test indicated that nitrate and salinity were key environmental factors influencing α diversity. RDA analysis revealed that the dominant species in spring were mainly influenced by chlorophyll-a and water temperature, while those in summer were mainly affected by water depth, nitrite, water temperature, and salinity.

Sequential migrations of diverse fish community provide seasonally prolonged and stable nutrient inputs to a river.

Animal migrations transport resources among spatially separate ecosystems, effectively linking them. In freshwater ecosystems, numerous fish species migrate between mainstream rivers or lakes and their tributaries, providing resources and nutrients during their spawning migrations. Multiple migratory species travel to the same destinations and contribute such nutrients, but knowledge remains limited about how the diversity of migratory animals influences the recipient ecosystem. We investigated how migrations of diverse fish community from Lake Biwa, Japan contribute to nutrient inputs in one of the lake's tributary rivers and how they influence the ecosystem. Sequential migration of six fish species continued for 8 months of a year, causing high-level nutrient concentration and primary production. The fish-derived resources were taken up by diverse members of the river community. Our results emphasize the extent to which migrations of diverse animals seasonally extend and stabilize the resource subsidy and how they extend pronounced effects on the recipient ecosystems.

Important fish diversity maintenance status of the tributaries in a hotspot fish conservation area in the upper Yangtze River revealed by eDNA metabarcoding

This study employed Environmental DNA (eDNA) barcoding technology to delve into the influence of the tributaries and mainstem on fish diversity and spatiotemporal distribution in a hotspot fish conservation area in the upper Yangtze River. A total of 123 fish species were detected, belonging to 7 orders, 19 families, and 77 genera. The composition of fish species in tributaries is similar to that in mainstem, with higher fish community diversity in tributaries during the spring and summer. Exploration of fish ecotypes revealed significant differences between mainstem and tributaries. The fish community is mainly influenced by key environmental factors such as water temperature, dissolved oxygen, electrical conductivity, and ammonia nitrogen, with a higher impact of these factors on tributaries than on mainstem. In conclusion, while tributaries and mainstem in the Jiangjin section exhibit similarities in fish community composition, there are notable differences in community structure and diversity. Therefore, the protection of not only mainstem but also tributaries and their associated fish habitats is crucial for promoting the overall health and sustainability.

Increased diversity of macroinvertebrates, but not fish, near wastewater outfalls in the Red River Basin, Oklahoma

The reuse of wastewater for beneficial purposes (e.g. irrigation) can boost water sustainability, but may have positive or negative impacts on the environment. In some drought-prone or over-allocated river basins, wastewater is an important component of stream flows and may buffer river ecosystems from drought. In these locations, wastewater may have a net positive impact on river ecosystems and its capture and reuse would be harmful to these ecosystems. In other locations, wastewater may have a net negative impact if the quality of the wastewater (i.e. concentrations of contaminants and nutrients) is lower than that of the receiving water body. In this study, we quantified the effects of wastewater on fish and macroinvertebrate communities in the Red River, Oklahoma. We investigated two competing hypotheses. First, we hypothesized that if wastewater flows buffer aquatic communities from drought, then measures of biodiversity should be higher at sampling sites near wastewater outfalls than at sites not near wastewater outfalls. Second, we hypothesized that if wastewater outfalls negatively impact water quality or homogenize the flow regime, then measures of biodiversity should be lower at sites near wastewater outfalls. To test these competing hypotheses, we calculated a suite of biodiversity indices at 320 biological sampling sites in the Red River Basin and analyzed for significant differences in communities based on proximity to wastewater outfalls. We found that proximity to upstream wastewater outfalls had significant positive impacts on macroinvertebrate community biodiversity, but we did not find any significant relationships with fish community diversity. Findings from this study provide insight to management decisions on wastewater reuse initiatives in beneficial subbasins while minimizing harmful ecological impacts.

Характеристика прибрежной ихтиофауны губ Восточного Мурмана в летний период 2021 года

In the article was considered species composition of fish in the littoral and sublittoral zones of Yarnyshnaya and Zelenetskaya bays (Barents Sea) during summer 2021. Also quantitative characteristics of the distribution for each fish species are represented. The dynamics of abundance and diversity of coastal fish communities were analyzed. At whole was discovered 12 species of fish and most abundent between them is young saithe Pollachius virens. Comparing of perennial data with 2021 indicates that at the present observed average species composition, fish distribution density, abundance of young Gadidae and indicators of biodiversity in coastal communities.

Environmental DNA reveals spatial and temporal variation in fish communities before the 10-year fishing ban in the Poyang Lake Basin

Poyang Lake is the largest freshwater lake in China, and its unique ecosystem is an important biodiversity reservoir. Fish play an important role in the aquatic ecosystem of Poyang Lake. Accurate assessment of fish species diversity and community composition is essential for studies of fish ecology and conservation management. In this study, environmental DNA metabarcoding was used to analyze fish diversity and community structure in different habitats and seasons in the Poyang Lake Basin. A total of 52 fish species were identified, and limnicolous fish were the most abundant; most fish were omnivorous and small. The fish diversity index was highest in the spring and in the main lake area of Poyang Lake. Cluster analysis and non-metric multidimensional scaling analysis revealed significant differences in fish community structure among habitats. Water temperature and pH were the main environmental factors affecting fish community structure in the Poyang Lake Basin. Non-invasive environmental DNA monitoring methods could provide an important auxiliary method for monitoring fishery resources during the 10-year fishing ban period. This study provides basic information on the fish resources in the Poyang Lake Basin and has implications for fishery management and the development of ecological protection policies.

Spatial Distribution Patterns and Beta Diversity of Fish Communities in a Tropical River Basin of Deccan Plateau

ABSTRACTRiverine ecosystems exhibit significant spatial variations in their communities, and understanding of these variances is vital to comprehend the mechanisms that maintain biodiversity. This study was conducted to understand pattern of distribution and beta diversity of fish communities in the Bhima River basin in the Deccan Plateau region of India. Fish distribution data from 59 sites across 11 rivers of the Bhima River basin were collected, and pair‐wise βDissimilarity and site‐wise local contribution to beta diversity (LCβDSorensen) and its components (LCβDTurnover and LCβDNestedness) were calculated. Power function regression was analysed to understand the decay in community similarity with geographical and environmental distances. Redundancy analysis was performed to investigate the relationship between fish distribution and environmental variables. Results indicated that species richness declined with increasing longitude from west to east. A negative relationship was observed between species richness and LCβDSorensen. LCβDTurnover formed Ո‐shaped curve at both ends of the species richness gradient, while LCβDNestedness values exhibited Ս‐shaped curve. No significant difference between mean LCβDTurnover and mean LCβDNestedness across the sites was observed. The distance decay relationship between community similarity and both geographical and environmental distances follows the power law shape, and the slope of this relationship flattened with increasing distance. Precipitation, topography, temperature variation and dissolved oxygen played a pivotal role in shaping fish assemblages. This study provides insight into the spatial distribution of fish communities in the Bhima River basin, which will be helpful to comprehend the ordination of biodiversity in the riverine ecosystem of the Deccan Plateau region.

The native fish diversity with environmental influencing factors in the Daqing River basin, China

IntroductionInvestigating and assessing native fish diversity and conducting regional assessments of threats are vital for the conservation of aquatic biodiversity. For this specific study, the Daqing River basin in China was chosen as the research area. Field surveys were carried out between 2018 and 2019, supplemented by a review of pertinent literature and other records.MethodsTo evaluate fish diversity, the following parameters are selected for analysis: Relative abundance (Pi), Frequency of occurrence (Fi), Margalef richness index (D) , Shannon Wiener diversity index (H′) , and Pielou evenness index (J′).Relative abundance levels are categorized as follows: dominant species make up more than 10%, common species account for 1%–10%, and occasional species constitute less than 1%. Canoco 5.0 software was utilized to conduct Redundancy Analysis (RDA) on the fish species composition and environmental factors at 34 sampling sites.ResultsThe findings revealed that 85 fish species have been recorded in the basin, consisting of 78 freshwater species categorized into 8 orders, 17 families, and 59 genera, among which Cypriniformes comprised 64% of the total catch. The low proportion of threatened and endemic species was an important feature of the fish diversity of the Daqing River. Despite the theoretical presence of 85 species, field surveys managed to collect only 42 species, of which 33 were confirmed as naturally occurring within the basin. The average values of Margalef richness index, 22 Shannon Wiener diversity index and Pielou evenness index were 1.72, 2.04 and 0.80 respectively, signifying a low fish diversity with relatively uniform distribution across the sampled regions.DiscussionThis study found that the community structure and diversity of fish were closely related to environmental factors, particularly water quality. Among these factors, ammonia nitrogen emerged as a significant determinant of fish diversity. High concentrations of ammonia nitrogen inhibit fish growth, endanger health, and can even lead to death. Additionally, dams and other water infrastructure also impact fish community structure and diversity. This baseline study can provide a basis for the protection and ecological restoration of fish resources in the Daqing River.

Diversity, functional redundancy, and vulnerability of reef fish communities of the Saudi Arabian coast, in the northern Red Sea

In light of the current development of several giga-projects along the Saudi Red Sea coast, understanding the health status of coral reefs is paramount to developing baselines and management strategies to minimize the human impact on these ecosystems. Here, we present an assessment of the diversity, functional redundancy, and vulnerability for coral reef fish communities in the northern Red Sea. The focus area of our study falls within the marine jurisdiction of the NEOM giga-project. We performed fish surveys with three different methods aiming to cover a wide set of habitats and thus capture a comprehensive picture of the regional diversity: i) standardized belt transects, ii) roving diviersity surveys, and iii) collection of cryptobenthic fish. Our results showed a highly variable community composition along the ten surveyed sites highlighting Sindalah as an essential site for piscivore species, Al Muwaileh as an important site for herbivores, and Sanafir-Tiran as the most diverse site. Functional diversity analysis revealed similar levels of redundancy, over-redundancy, and vulnerability among sites. Functional richness, evenness, and divergence did not vary substantially between sites and, in general, indicated that the fish communities in the selected sites present mid to low levels of functional diversity. We further compare regional-scale and site-specific functional assessments. Notably, some of the species groups that are functionally redundant at the regional scale represented vulnerable functions at the site level. These results call to attention the need to create site-specific conservation strategies and not to solely rely on regional diviersity assessments as the basis for management decisions.

Environmental DNA Reveals the Impact of Submarine Groundwater Discharge on the Spatial Variability of Coastal Fish Diversity.

Submarine groundwater discharge (SGD) has recently been recognized as an influential factor in coastal ecosystems; however, little research has been conducted on its effects on coastal fish diversity. To investigate the relationship between SGD and fish diversity, we conducted a survey at the coastal island scale using the environmental DNA (eDNA) method. Our findings indicate that fish species richness and functional richness peak at stations with high SGD. Environmental variables, such as salinity, dissolved inorganic nitrogen (DIN) concentration, and SGD, significantly influence fish diversity. Carnivore fish richness was negatively correlated with salinity, while planktivore fish richness was positively correlated. Additionally, SGD and DIN concentrations were found to be crucial in shaping omnivorous and pelagic communities, respectively. This study highlights the role of SGD in enhancing nutrient conditions favorable for diverse fish communities and demonstrates the effectiveness of eDNA metabarcoding for rapid marine biodiversity assessment. These findings provide valuable insights for coastal ecosystem monitoring and management.

Initial Alterations of Fish Community Structure and Diversity Following Fishing Cessation in Qilu Lake, China.

The Qilu Lake is an eutrophic shallow lake located in Yunnan Province, China. An ecological fishery project was initiated in the lake from 2011 to 2021 to introduce filter-feeding fish species that feed on algae, with the aim of improving water quality. In January 2022, when the ecological fishery project expired, all fisheries-related activities (including fish stocking and fishing activities) ceased in the lake. To comprehensively evaluate the initial alterations in fish community structure and diversity resulting from the fishing cessation in the Qilu Lake, the present study conducted field surveys within the one year before the fishing cessation (referred to as BFC) and the one year after the fishing cessation (referred to as AFC). A total of twenty-one fish species were collected, including four native species. Four species were recorded in the lake for the first time, including Pelteobagrus fulvidraco, Pelteobagrus vachelli, Paramisgurnus dabryanus, and Hyporhamphus intermedius. The number of fish species decreased from 21 to 13 following the fishing cessation. The fishes collected in both BFC and AFC are mainly omnivorous-feeding and of bottom-dwelling habits. The mean size of the fishes in the AFC sample shows a significant decrease compared to those in BFC. After the fishing cessation, the Shannon-Wiener diversity index and Margalef richness index of the fish slightly declined. The fish community structure of the Qilu Lake exhibits a high degree of similarity to adjacent lakes in central Yunnan. Our study demonstrates a significant shift in the fish community of the Qilu Lake following the fishing cessation, one which may adversely impact the stability of the lake ecosystem. To enhance fish species diversity in the Qilu Lake, it is recommended that policies be implemented to promote the ecological fishery project and improve habitat restoration for native fish species, while also regulating fish community structure.

Community Structure Characteristics and Changes in Fish Species at Poyang Lake after the Yangtze River Fishing Ban

To understand the fish community structure characteristics and changes in Poyang Lake after the Yangtze River fishing ban in 2021, seven sampling stations were established, namely in Hukou, Lushan, Duchang, Yongxiu, Nanjishan, Ruihong, and Poyang, for fishery resource surveys between 2020 and 2021. The results showed that 93 fish species were identified, belonging to 11 orders, 20 families, and 61 genera, which was an increase of 4.5% from before the fishing ban. Of these, 52 Cyprinidae species were identified, comprising the highest proportion (55.91%). Four invasive alien species (hybrid sturgeon, Cirrhina mrigala, Piaractus brachypomus, and Mugil cephalus) were identified, and the number of alien species in Poyang Lake was higher than before the fishing ban. Carnivorous and mid-lower-level fish showed a significant increase, accounting for 47.31% and 38.71% of the total species, respectively. Compared with the Yangtze River before the fishing ban, the body length and body weight of the main economic fish in Poyang Lake increased by 6.10–61.26% and by 15.14–291.57%, respectively. In terms of age structure, the proportion of major economically important fish aged 1 or 2 years decreased significantly, while the proportion of older fish increased substantially. There was little difference in the diversity of fish communities at different stations in Poyang Lake. In terms of biodiversity, the Shannon–Wiener index ranged from 2.158 to 2.909, with Poyang having the highest value and Nanjishan the lowest. Margalef’s index ranged from 4.265 to 6.459, with Lushan having the highest value and Nanjishan the lowest. Pielou’s index ranged from 0.617 to 0.822, with Duchang having the highest value and Nanjishan the lowest. Hence, the Yangtze river fishing ban has played an important and positive role in the restoration of fishery resources in Poyang Lake. However, long-term tracking and monitoring are needed to provide information to comprehensively evaluate the ecological impact of the Poyang Lake fishing ban.

Fish Diversity and Water Quality in Munroe Island, Kollam District, Kerala

Munroe Island, located in the Kollam district of Kerala, is renowned for its rich biodiversity and picturesque landscapes. The present study aimed to assess the fish diversity and water quality in the Munroe Island region of Kollam District, Kerala. The ichthyofaunal survey conducted in the area (3 sites) revealed the presence of 23 fish species belonging to 18 families, indicating a diverse fish community in the region. However, threat status assessment using IUCN criteria identified several species as vulnerable or near threatened to anthropogenic pressures. The analysis of physico-chemical parameters of water quality (from 10 sites) highlighted various factors influencing ecosystem dynamics, including temperature fluctuations, pH levels, dissolved oxygen concentrations, and levels of organic pollutants, BOD and COD. Additionally, the presence of ions such as chloride, sulphate, and nitrate suggested potential sources of contamination and pollution due to anthropogenic activities. These findings emphasize the importance of integrated conservation and management strategies to preserve the ecological integrity of Munroe Island’s aquatic ecosystems and ensure the long-term sustainability of fish populations.

Spatiotemporal Variations in Trophic Diversity of Fish Communities in a Marine Bay Ecosystem Based on Stable Isotope Analysis

Climate change has led to significant fluctuations in marine ecosystems. As a component of the food web, the trophic diversity and spatiotemporal changes of fish communities are crucial for understanding ecosystems. In recent years, stable isotope analysis has been increasingly used as a comprehensive tool for quantitative assessment of trophic diversity to explore spatiotemporal variations in fish community diversity. This study is based on carbon (δ13C) and nitrogen (δ15N) stable isotope analysis using different biomass-weighted isotope diversity indices, including isotopic divergence index (IDiv), isotopic dispersion index (IDis), isotopic evenness index (IEve), and isotopic uniqueness index (IUni). The overall results indicate that IDis, IEve, and IUni values of fish communities were relatively low, while IDiv was relatively high in the Haizhou Bay ecosystem. IDiv, IDis, IEve, and IUni were lower in autumn than in spring; IDiv and IDis were relatively higher in offshore waters, while IEve and IUni were relatively higher in inshore waters. The changes in species composition and intensive pelagic–benthic coupling in Haizhou Bay may lead to significant spatiotemporal variations in the trophic diversity of fish communities in the area. These findings highlight the importance of incorporating trophic relationships into ecosystem models, which will help to enhance our understanding of the complexity of the trophic structure of fish communities.

Towards a comprehensive assessment of ichthyofaunal diversity in the Yangtze River estuary: Leveraging environmental DNA technology and bottom trawl surveys

The fishery resources in the Yangtze River Estuary (YRE) have declined drastically because of overfishing and environmental changes, leading to ecosystem degradation of the YRE, and bringing numerous rare fish species to the brink of extinction. As a new technology with great prospects for popularization and application, environmental DNA (eDNA) technology has been utilized and proven by many studies to have high potential in revealing the various species' biodiversity. In this study, we analyzed the species composition and diversity of the Yangtze River Estuary using a combination of eDNA technology and bottom trawling approaches, and later, the comparison of both methods. The results showed that combining eDNA technology and bottom trawling, 30 fish species from 7 orders and 11 families were identified. Among the 30 fish species, a total of six species of fish could be observed in catches from both methods. Perciformes were the most abundant and Coilia mystus was the dominant species. According to diversity indices, the eDNA technology reveals significant differences in fish community richness and diversity in the Yangtze River Estuary compared to the bottom trawl. In summary, the eDNA technology is feasible for monitoring fishery resources in the waters of the Yangtze River Estuary, thereby serving as a valuable supplementary tool for conducting comprehensive surveys in this region. Moreover, it holds significant implications and promising prospects for conserving the diverse ecosystem of the YRE in future conservation efforts.