GROWTH, PRIMARY PRODUCTIVITY, AND NITROGEN FIXATION POTENTIAL OF NODULARIA SPP. (CYANOPHYCEAE) IN WATER FROM A SUBTROPICAL ESTUARY IN THE UNITED STATES

Nodularia is a halotolerant, filamentous, dinitrogen-fixing cyanobacterium that forms massive blooms in some coastal oceans, estuaries, and saline lakes worldwide. Although the genus is globally distributed, its blooms are sporadic and appear to be confined to certain water bodies. Blooms are frequently associated with phosphorus enrichment; therefore Nodularia may benefit from increased anthropogenic nutrient loading to coastal waters. We studied the potential for Nodularia to grow in the nitrogen-limited Neuse River Estuary (North Carolina, U.S.A.) with laboratory growth experiments in Neuse River Estuary water and by examining physico-chemical data from the estuary. Analysis of nutrients (nitrogen and phosphorus), salinity, and temperature data from the Neuse River Estuary between 1994 and 1998 revealed that suitable conditions for Nodularia prevailed during the summer of each of these years for time spans ranging from 1.5 to 5 months. Growth of two laboratory strains in Neuse River Estuary water was as fast or slightly slower than in artificial growth medium, as long as the culture inoculum had phosphorus reserves. Phosphorus addition did not stimulate growth of already phosphorus-sufficient inocula. Phosphorus starvation of the inoculum before the experiment decreased growth rates in the estuarine water unless additional phosphorus was supplied. Although phosphorus addition had a stimulatory effect on dinitrogen fixation and productivity, the effect differed for the two Nodularia strains. Results suggest that growth of Nodularia in North Carolinian estuaries is possible, and that such growth would be phosphorus-limited at times. Phosphorus availability may determine the times and locations for potential establishment of Nodularia in this and similar estuarine ecosystems.     

Fish habitat modelling as a tool for river management

This paper presents an integrated modelling approach to simulate and assess ecological effects of physical habitat changes in rivers. An ecohydraulic simulation tool was created by combining a 1D hydraulic model based on HEC-RAS software and the fish habitat module of CASiMiR, a fuzzy logic-based ecohydraulic modelling system. This tool was applied on a river stretch commonly occurring in Belgium and elsewhere in Europe. In particular the effect of weir removal on habitat suitability for bullhead (Cottus gobio L.) was simulated. Physical conditions of the studied stretch after weir removal were simulated with a hydraulic model. CASiMiR linked these conditions to ecological expert knowledge to calculate habitat suitability for three life stages of bullhead at four different flow rates based on fuzzy logic. Results indicated that after weir removal, habitat suitability increased significantly for all life stages and all flow rates. The presented approach is promising regarding fish community assessment and ecological river engineering.     

RESPONSES OF THE PHYTOPLANKTON COMMUNITY GROWTH RATE TO NUTRIENT PULSES IN VARIABLE ESTUARINE ENVIRONMENTS

In estuaries, phytoplankton are exposed to rapidly changing conditions that may have profound effects on community structure and function. In these experiments, we evaluated the growth, productivity, and compositional responses of natural phytoplankton communities exposed to limiting nutrient additions and incubation conditions typical of estuarine habitats. Mesocosm bioassays were used to measure the short-term (2-day) growth rate, primary productivity, and group-specific biomass responses of the phytoplankton community in the Neuse River Estuary, North Carolina. A three-factor (mixing, sediment addition, and nutrient addition) experimental design was applied using 55-L mesocosm tanks. Growth rates were determined using the ¹⁴C photopigment radiolabeling method, and the abundance of algal groups was based on quantification of chemosystematic photopigments by HPLC. For Neuse River Estuary phytoplankton communities, stratified (nonmixed), turbid, and low-nitrate conditions favored increases in cryptomonad biomass. Mixed, turbid, high-nitrate conditions were favorable for increased primary productivity and chlorophytes, diatoms, and cyanobacteria. The highest community growth rates occurred under calm, high-nitrate conditions. This approach provided an assessment of the community-level phytoplankton responses and insights into the mechanisms driving blooms and bloom species in estuarine waters. The ability to rapidly alter growth rates to capitalize on conditions conducive for growth may play an important role in the timing, extent, and species involved with blooms in estuarine waters. Adaptive growth rate responses of individual species, as well as the community as a whole, further illustrate the sensitivity of estuarine ecosystems to excessive N inputs.     

Fish assemblage in the Pearl River Estuary: Spatial‐seasonal variation,environmental influence and trends over the past three decades

The Pearl River Estuary is the largest estuary in South China and plays a considerable role in the local fisheries economy, yet little is known about the current state of fish assemblage in this ecosystem. To quantify spatial‐seasonal variations, environmental influences, and trends over the past three decades of the fish assemblage in the Pearl River Estuary, we sampled 11 sites seasonally from December 2013 to September 2016. Throughout the study, 285 species from 88 families and 195 genera were collected. There were obvious spatial and seasonal variations of the fish assemblage in terms of the dominant species, species richness, and composition of ecological types. Mouth distance, NH₄⁺ N, chlorophyll‐a, flow, DO, salinity and water transparency were the main variables influencing the spatial‐temporal dynamic of fishes within the estuarine systems. Compared with the record of 330 species in the 1980s, the number of fish species in the Pearl River Estuary has declined by 45 fish species. The Jaccard's similarity of fish composition between the historical investigation (the 1980's) and the present investigation (2013–2016) was 0.62, with 95 species undiscovered and 50 species increased in the present study compared to the 1980s, indicating the assemblage structure has obviously changed. However, in term of ecological guilds, there was no significant difference in the composition of all the selected ecological traits between these two periods. Anthropogenic activities including overfishing, introducing alien fish, dam construction and pollution were considered the main disturbance on fish composition over the past three decades. We conclude that there existed pronounced spatiotemporal changes of fish assemblages, which arises from the compounding effects of environmental factors and anthropogenic activities. These findings are beneficial to understanding and developing suitable conservation strategies for the management and protection of fish resources in the Pearl River Estuary.     

基于环境DNA宏条码和底拖网的珠江河口鱼类多样性

文章采用环境DNA宏条码和底拖网对珠江河口鱼类多样性进行了研究, 并对两种方法进行了比较。利用环境DNA宏条码检测到了175种鱼类, 而利用底拖网采集到了47种鱼类, 结合两种方法共检测出179种鱼类, 隶属于15 目63科128属。其中两种方法共同识别了鱼类43种, 占总检测物种的24.02%, 基于底拖网的调查未能收集到基于环境DNA宏条码检测到的大多数物种。根据Shannon指数和Simpson指数显示, DNA宏条码所检测珠江河口鱼类群落α多样性显著高于底拖网方法(P<0.05)。两种方法的PCoA结果均显示珠江河口鱼类群落存在空间结构, 基于环境DNA宏条码的分析显示空间重叠更多。两种方法基于冗余分析均显示溶解氧和盐度是影响鱼类群落结构的主要环境因子。研究表明, 环境DNA 宏条形码是一种环保且可靠的评估方法, 将其搭载到现有调查可以更好地了解河口鱼类多样性。     

Enhancing Causal Assessment of Estuarine Fishkills Using Graphical Models

It is not possible to determine the causal relationship between fishkills and the toxic dinoflagellate Pfiesteria piscicida in the Neuse River Estuary, North Carolina, using observational data on these two variables alone. However, consideration of a third variable, indicating the presence of a broader class of more easily measured Pfiesteria-like organisms (PLOs), leads to causal model structures from which the nature of this relationship can be distinguished. We use reported field data to evaluate alternative models and find that the suggestion that toxic Pfiesteria cause fishkills is inconsistent with observation. The data are more indicative of a model in which PLOs (including potentially toxic Pfiesteria) are stimulated to become actively toxic by the presence of already dead or dying fish. Laboratory experiments performed to date do not provide evidence contradictory to this finding. However, neither can the existence of a common cause of both Pfiesteria toxicity and fishkills be ruled out. The differing implications for ecosystem management suggest that these causal associations should be further investigated through additional modeling and data collection efforts. Graphical methods of model construction and evaluation can assist in this process. Received 22 May 2002; accepted 3 October 2002.     

Salinity effects on growth,photosynthetic parameters,and nitrogenase activity in estuarine planktonic cyanobacteria

Salinity has been suggested as being a controlling factor for blooms of N2-fixing cyanobacteria in estuaries. We tested the effect of salinity on the growth, N2 fixation, and photosynthetic activities of estuarine and freshwater isolates of heterocystous bloom-forming cyanobacteria. Anabaena aphanizomenoides and Anabaenopsis sp. were isolated from the Neuse River Estuary, North Carolina, and Cylindrospermopsis raciborskii from Lakes Dora and Griffin, central Florida. Salinity tolerance of these cyanobacteria was compared with that of two Nodularia strains from the Baltic Sea. We measured growth rates, N2 fixation (nitrogenase activity), and CO2 fixation at salinities between 0 and 20 g L(-1) NaCl. We also examined photosynthesis-irradiance relation-ships in response to salinity. Anabaenopsis maintained similar growth rates in the full range of salinities from 2 to 20 g L(-1) NaCl. Anabaena grew at up to 15 g L-', but the maximum salinity 20 g L(-1) NaCl was inhibitory. The upper limit for salinity tolerance of Cylindrospermopsis was 4 g L(-1) NaCl. Nodularia spp. maintained similar growth rates in the full range of salinities from 0 to 20 g L(-1) . Between 0 and 10 g L(-1), the growth rate of Nodularia spumigena was slower than that of the Neuse Estuary strains. In most strains, the sensitivity of nitrogenase activity and CO2 fixation to salinity appeared similar. Anabaenopsis, Anabaena, and the two Nodularia strains rapidly responded to NaCl by increasing their maximum photosynthetic rates (Pmn). Overall, both Neuse River Estuary and Baltic Sea strains showed an ability to acclimate to salt stress over short-(24 h) and long-term (several days to weeks) exposures. The study suggested that direct effect of salinity (as NaCl in these experiments) on cyanobacterial physiology does not alone explain the low frequency and magnitude of blooms of N2-fixing cyanobacteria in estuaries.     

GAM模型和BRT模型在长江口鱼类群落多样性预测中的比较

长江口为西太平洋最大的河口,评估其鱼类群落多样性分布能够为长江口生态系统的修复和管理提供科学依据.本研究基于2012—2014年长江口渔业监测数据,分别使用GAM模型和BRT模型建立各站点水域鱼类群落多样性指数与环境和时空因子之间的关系.结合线性回归方程,采用交叉验证的方式对模型的预测能力和拟合效果进行评价,并绘制了2014年长江口鱼类群落多样性指数和丰富度指数的空间分布图.结果表明: 盐度、pH和叶绿素a对多样性指数贡献最高,pH、溶解氧和叶绿素a是对丰富度指数贡献率最高的环境因子.BRT模型对于多样性指数和丰富度指数的拟合和预测结果均优于GAM模型.空间分布预测显示,相较于GAM模型,BRT模型能够对长江口小面积水域间的鱼类群落多样性作更好的区分,河口外侧水域的鱼类群落多样性明显高于河口内侧水域,而北支水域的多样性高于南支水域.     

Fish mortality and physicochemistry in a managed floodplain wetland

Patterns of fish mortality and associated physicochemical factors werestudied during late spring in a managed wetland canal along the lowerMissouri River, Missouri. Mean dawn dissolved oxygen was lower and meanun-ionized ammonia and turbidity were higher during the fish kill thanbefore or after the kill, or than was observed in a nearby wetland canalwhere no fish kill occurred. Dissolved oxygen at dawn and un-ionizedammonia concentrations were at critically low and high levels respectively,so that both likely contributed to the fish mortality. Timing and magnitudeof observed carcasses suggested that Ameiurus melas Rafinesques wasthe most tolerant species for the sizes observed compared to Ictiobuscyprinellus Valenciennes, Lepomis macrochirus Rafinesque, Cyprinus carpio Linneaus, and Lepomis cyanellus Rafinesque.Decreasing mean lengths of fish carcasses during the fish kill for C.carpio, L. cyanellus, and A. melas, indicate that smaller fishes mayhave been more tolerant of harsh environmental conditions than largerindividuals of the same species. Differential mortalities among species andsizes during drawdowns in actively managed wetland pools may haveintentional and unintentional ramifications on wetland and riverine fishcommunity structure, fish-avian interactions, and implementing anecosystem management perspective to restoring more naturalized riverfloodplain wetland functions. Late summer and early autumn draining ofmanaged wetlands might be used to benefit a wider diversity of wildlife andfishes.     

Diet overlap and resource partitioning among three forage fish species in Coorong,the largest inverse estuary in Australia

Protracted drought in southern Australia has degraded the system function of the Coorong estuary and intensified resource competition among forage fish species. The present study investigates the gut content, prey composition and dietary overlap of three forage fishes: smallmouth hardyhead (Atherinosoma microstoma), Tamar River goby (Afurcagobius tamarensis) and sandy sprat (Hyperlophus vittatus) influenced by environmental variation in the Murray Estuary and Coorong. The prey species identified in fish stomachs were dominated by crustaceans (amphipods, ostracods and harpacticoids), but nematodes and acanthocephalans were also common in all forage fishes. The diet of the sandy sprat and Tamar River goby highly overlapped (α = 0.8) in the Murray Estuary and all three forage fishes showed potential diet overlap (α ≥ 0.6) in the North Lagoon. Spatiotemporal variation of prey diversity was observed in smallmouth hardyhead while temporal variation of prey diversity was observed in sandy sprat and Tamar River goby. Overall, the prey abundance was temporally variable and predominantly regulated by salinity, pH, dissolved oxygen, water transparency and chlorophyll a in the Murray Estuary and Coorong. This study adds to our knowledge on dietary overlap and resource partitioning among small-bodied forage fishes mediated by environmental factors in the Murray Estuary and Coorong.     

Dynamics and predictive modelling of Vibrio spp. in the Neuse River Estuary, North Carolina, USA

Vibrio spp. are naturally occurring bacteria in marine and estuarine environments around the world. The genus includes several human and animal pathogens that can negatively impact human health, seafood and aquaculture. Vibrio spp. populations are capable of rapid adaptation in response to changing environmental conditions, making them dynamic over short-term and seasonal scales. Temperature, vertical mixing, tidal flushing, climate, precipitation and nutrient loading can change the estuarine environment and subsequently alter microbial community structure, including Vibrio spp., affecting estuarine water quality and public health. To describe these dynamics, Vibrio spp. concentrations and a range of microbial, physical and chemical measures were monitored every 2 weeks and after storm events for 19 months in the Neuse River Estuary (NRE). Results showed clear seasonal and geographic trends in Vibrio spp. abundance. Multiple regression analysis revealed a strong relationship to temperature and salinity, with additional minor influences of chlorophyll a and dissolved organic carbon. Similar models based on easily measured environmental parameters should be pursued for individual Vibrio species in the NRE and other estuarine environments. Predictive models provide useful information for managers, researchers and modellers of estuarine ecosystems.     

Antioxidant Defenses in Fish: Biotic and Abiotic Factors

Oxygen in its molecular state O₂, is essential for many metabolic processes that are vital to aerobic life. Aerobic organisms cannot exist without oxygen, which nevertheless is inherently dangerous to their lives. Like all aerobic organisms, fish are also susceptible to the effects of reactive oxygen and have inherent and effective antioxidant defenses that are well described in the literature. This review investigates the influence of different biotic and abiotic factors (age, phylogenetic position, feeding behavior, environmental factors, oxygen, temperature, presence of xenobiotics) on antioxidant defenses in fish. Studies of antioxidant activity in fish open a number of novel research lines providing greater knowledge of fish physiology, which will benefit various aspects of fish farming and artificial production.     

Form or Function: A Comparison of Expert and Novice Judgments of Similarity Among Fish

Ethnobiologists debate whether folk biological classifiers are natural historians attending primarily to the morphology of organisms or are pragmatists concerned primarily with utility. We argue that this question is best understood as a problem in intracultural variation: the relative importance of form and function depends on who is asked to judge the similarity of organisms as well as how they are asked to judge it. We find that expert fishermen judge similarities among fish on both functional and morphological criteria, while novices judge on morphological criteria alone and thereby approach the scientific classification of fish more closely than experts. Experts also vary more than do novices, presumably because they control more different kinds of knowledge on which to base a similarity judgment.     

Fish track wastewater pollution to estuaries

Excess nitrogen is a forceful agent of ecological change in coastal waters, and wastewater is a prominent source of nitrogen. In catchments where multiple sources of nitrogen pollution co-exist, biological indicators are needed to gauge the degree to which wastewater-N can propagate through the receiving food webs. The purpose of this study was to test whether estuarine fish are suitable as indicators of sewage-N pollution. Fish were analysed from three estuaries within a 100-km strip on the Australian East Coast. The estuaries differ substantially in wastewater loading: (1) the Maroochy Estuary receives a large fraction of the local shire’s treated sewage, (2) the Mooloolah Estuary has no licensed treated wastewater outfalls but marinas/harbours and stormwater may contribute nitrogen, and (3) the Noosa Estuary which neither receives licensed discharges nor has suspected wastewater loads. Sampling for fish included both high rainfall (‘wet’ season) and low rainfall (‘dry’ season) periods. Muscle-δ¹⁵N was the variable predicted to respond to treated wastewater loading, reflecting the relative enrichment in ¹⁵N resulting from the treatment process and distinguishing it from alternative N sources such as fertiliser and natural nitrogen inputs (both ¹⁵N-depleted). Of the 19 fish species occurring in all three estuaries, those from the Maroochy Estuary had significantly elevated δ¹⁵N values (up to 9.9‰), and inter-estuarine differences in fish-δ¹⁵N were consistent across seasons. Furthermore, not only did all fish from the estuary receiving treated wastewater carry a very distinctive sewage-N tissue signal, but enriched muscle-δ¹⁵N was also evident in all species sampled from the one estuary in which sewage contamination was previously only suspected (i.e. the Mooloolah Estuary: 0.2–4.8‰ enrichment over fish from reference system). Thus, fish-δ¹⁵N is a suitable indicator of wastewater-N not only in systems that receive large loads, but also for the detection of more subtle nitrogen inputs. Arguably, fish may be preferred indicators of sewage-N contamination because they: (1) integrate nitrogen inputs over long time periods, (2) have an element of ‘ecological relevance’ because fish muscle-δ¹⁵N reflect movement of sewage-N through the food chain, and (3) pollution assessments can usually be based on evidence from multiple species.     

Development and Application of a Predictive Model of Freshwater Fish Assemblage Composition to Evaluate River Health in Eastern Australia

Multivariate predictive models are widely used tools for assessment of aquatic ecosystem health and models have been successfully developed for the prediction and assessment of aquatic macroinvertebrates, diatoms, local stream habitat features and fish. We evaluated the ability of a modelling method based on the River InVertebrate Prediction and Classification System (RIVPACS) to accurately predict freshwater fish assemblage composition and assess aquatic ecosystem health in rivers and streams of south-eastern Queensland, Australia. The predictive model was developed, validated and tested in a region of comparatively high environmental variability due to the unpredictable nature of rainfall and river discharge. The model was concluded to provide sufficiently accurate and precise predictions of species composition and was sensitive enough to distinguish test sites impacted by several common types of human disturbance (particularly impacts associated with catchment land use and associated local riparian, in-stream habitat and water quality degradation). The total number of fish species available for prediction was low in comparison to similar applications of multivariate predictive models based on other indicator groups, yet the accuracy and precision of our model was comparable to outcomes from such studies. In addition, our model developed for sites sampled on one occasion and in one season only (winter), was able to accurately predict fish assemblage composition at sites sampled during other seasons and years, provided that they were not subject to unusually extreme environmental conditions (e.g. extended periods of low flow that restricted fish movement or resulted in habitat desiccation and local fish extinctions).     

Nitrogen Loss Estimation Worksheet (NLEW): an agricultural nitrogen loading reduction tracking tool

The Neuse River Basin in North Carolina was regulated in 1998, requiring that all pollution sources (point and nonpoint) reduce nitrogen (N) loading into the Neuse Estuary by 30%. Point source N reductions have already been reduced by approximately 35%. The diffuse nature of nonpoint source pollution, and its spatial and temporal variability, makes it a more difficult problem to treat. Agriculture is believed to contribute over 50% of the total N load to the river. In order to reduce these N inputs, best management practices (BMPs) are necessary to control the delivery of N from agricultural activities to water resources and to prevent impacts to the physical and biological integrity of surface and ground water. To provide greater flexibility to the agricultural community beyond standard BMPs (nutrient management, riparian buffers, and water-control structures), an agricultural N accounting tool, called Nitrogen Loss Estimation Worksheet (NLEW), was developed to track N reductions due to BMP implementation. NLEW uses a modified N-balance equation that accounts for some N inputs as well as N reductions from nutrient management and other BMPs. It works at both the field- and county-level scales. The tool has been used by counties to determine different N reduction strategies to achieve the 30% targeted reduction.     

我国主要河口沉积物中多环芳烃细菌降解及生物修复强化方式的研究进展

河口是海洋及陆地交互作用的集中地带,其生态环境的健康状况对所在地区人类居住及社会经济的可持续发展十分重要。近年来,河口城市的快速发展导致了大量的多环芳烃(polycyclic aromatic hydrocarbons,PAHs)在河口沉积物中积累,持久地影响水生生态系统的健康,其降解与转化逐渐成为近年来的研究热点。本文总结发现,我国主要河口(珠江口、长江口、辽河口、海河口)沉积物中的PAHs降解菌主要分布于假单胞菌门、放线菌门及芽孢杆菌门,其中克雷伯氏菌属、芽孢杆菌属及假单胞菌属报道较多。在河口沉积物中,PAHs的细菌降解主要是通过低效率的厌氧降解途径。低氧、高盐度是PAHs细菌降解的不利条件,温度与pH值的变化也为实地生物修复的应用效率带来了不确定性。表面活性剂、营养物与外源电子受体的添加以及共代谢作用均可促进沉积物细菌对PAHs的降解。目前多数研究以实验室规模开展,而河口沉积物生境复杂,建议未来针对河口沉积物的环境特点进行PAHs降解功能菌株种质资源的挖掘,并根据实际情况灵活制定强化策略。本综述为进一步从我国主要河口沉积物中筛选PAHs高效降解菌及其利用提供了思路与参考。     

Restoration of the Kissimmee River: A Conceptual Model of Past and Present Fish Communities and Its Consequences for Evaluating Restoration Success

Efforts to restore fish communities of the Kissimmee River will require carefully defined criteria for assessing success. A goal of regaining communities mirroring those in the historical river may not be an appropriate target because the ecological conditions of the river before channelization are poorly known. The Kissimmee River is in a biogeographic region historically low in fish diversity, and no comparable rivers in that region remain substantially unaltered by human activity to permit their use as reference sites indicative of conditions in the Kissimmee before channelization. I propose alternative criteria for assessing restoration success emphasizing expectations for ecosystem function in similar floodplain rivers. Assessing ecosystem function will be less simple than assessing criteria such as fish condition or density of selected species. But criteria based solely on fish-population characteristics cannot be justified quantitatively. Information integrated from several levels of biotic organization (individuals, populations, communities, and systems) should be drawn upon in making conclusions about restoration success. I develop a conceptual model to outline aspects of ecosystem function that could serve as a basis for evaluation of the restoration of fish communities of the Kissimmee River. The model focuses on the dynamics of the flux of floodplain-channel nutrients and the movement of larvae, juvenile, and adult fishes and macroinvertebrates. The present community may be dominated more by species tolerant of low-oxygen conditions, such as gar and bowfin, than the restored community will be. I propose that nest sites may be the limiting recruitment success of substrate spawning species in the channelized river and that these species, including sunfish and large-mouth bass, will increase in abundance after restoration. Also, species relying on floodplain habitats, including sun-fish species, darters, and some minnows, may also increase in frequency with restoration of floodplain-channel hydro-logical conditions and habitats. The observation that no species are known to have disappeared from the Kissimmee River, and its relatively simple community structure compared to rivers of comparable size elsewhere, are encouraging for prospects of successful restoration.     

Fish assemblages of interior tidal marsh channels in relation to environmental variables in the upper San Francisco Estuary

Tidal marsh wetlands represent critical habitat for many estuarine fishes and are particularly important to conserving and restoring native and at-risk species. We describe the seasonal and regional variation in the composition and abundance of fishes in interior tidal marsh channels in the upper San Francisco Estuary (SFE), and relate these to variation in environmental conditions. Fish were sampled quarterly using modified fyke nets from October 2003 to June 2005 in 18 interior tidal marsh channels spanning 3 distinct river systems: Petaluma River, Napa River and West Delta. We collected 116 samples and 9452 individuals of 30 fish species. Four non-native species dominated—Mississippi silverside, western mosquitofish, yellowfin goby, and rainwater killifish—with an additional 13 species occurring commonly (represented equally by natives and non-natives, residents and transients). Large seasonal differences in composition and abundance of fishes occurred, with the lowest abundances in winter and spring and highest abundances in summer and fall. Correlation of ordination scores and environmental variables further supported the importance of season, as well as fish species’ status (native vs. non-native), feeding preference (pelagic vs. demersal), and marsh utilization (resident vs. transient), as factors influencing fish assemblage composition. The proximity of the marsh systems to freshwater and marine influences, which largely control salinity and temperature variation, explained 26% of the variation in fish composition, while channel geomorphology explained 22%. We recommend that both edge habitat (which may be beneficial to fish foraging success) and the extent of tidal connectivity (which allows access for fishes), in addition to location along the estuarine gradient, be considered in designing and managing tidal marsh restoration.     

黄河口及其邻近水域夏季鱼类群落空间格局及其与环境因子的关系

基于2013年夏季(6、7、8月)在黄河口及其邻近水域进行的渔业资源底拖网调查,应用多元分析方法研究了黄河口水域夏季鱼类群落空间结构,以及其与环境因子的关系.结果表明: 该海域夏季共捕获鱼类44种,隶属于11目25科40属,以暖温性和底层鱼类为主.经聚类分析,该海域夏季各月鱼类群落可大体划分为3个站位组.经单因子相似性分析(ANOSIM),黄河口不同水域鱼类群落物种组成存在显著差异.相似性百分比分析表明,矛尾虾虎鱼、斑鰶、短吻红舌鳎、蓝点马鲛和日本鳀等是各月份各站位组的典型种及造成不同站位组间群落差异的主要分歧种.典范对应分析(CCA)表明,影响夏季鱼类群落空间结构的主要环境因子为盐度、温度和深度.