太子河河流等级对鱼类群落结构及环境因子的影响

在河流生态学研究中河流等级是一种用于评价河流生物多样性及环境特征的重要分类标准。有研究表明不同河流等级中鱼类群落结构具有明显的差异性,但鱼类群落结构是否与河流等级及其影响的环境因子有明显的内在关联性还有待深入研究。本文以太子河流域为研究区域探究河流等级与鱼类群落分布之间的关系以及鱼类群落分布特征与环境因子之间的响应关系,并将太子河主要支流作为独立流域单元进行相同等级河流之间鱼类群落分布差异的比较。对太子河流域125个点位鱼类群落和水环境理化特征的调查结果显示,太子河流域鱼类群落结构在不同河流等级之间有显著差异,而且鱼类多样性与丰富度在三级河流最高,指示种分析表明洛氏鱥与北方条鳅是上游河段的指示种,短须颌须鮈与东北雅罗鱼是中游河段的指示种,?、大鳞副泥鳅及鰕虎鱼类是下游河段的指示种;摄食功能群在各级河流也有显著差异,杂食性鱼类的比例及物种数在三级河流和五级河流较高,昆虫食性的鱼类在一级河流和二级河流比例较高,昆虫食性鱼类的物种数在五级河流较高。 各等级河流之间总氮和氨氮有显著差异;相同等级河流之间鱼类群落结构也有显著的差异性,其电导率、水温和氨氮等环境因子具有显著差异性。本研究结果表明,太子河流域不同河流等级鱼类群落结构有显著的差异,相同等级河流的鱼类分布特征也有显著差异,但这种鱼类群落结构的空间差异性不受水环境理化因子的影响。     

辽河干流自然保护区鱼类群落结构及其多样性变化

2010年9月、2011年5月和8月对辽河干流自然保护区开展了鱼类调查。结果显示,保护区共有鱼类28种,以杂食性耐污小型鱼类为主,其中鲤科鱼类占65.52%。与历史资料相比,鱼类种类大幅减少,且表现出营养结构简单化、鱼类资源小型化的特征。保护区鱼类群落组成存在显著的空间变化,可分为石佛寺水库上游、石佛寺水库下游和感潮河段3个区段。保护区上游鱼类多样性和物种丰富度指数高于下游;鱼类物种数秋季高于春季,而鱼类个体数均匀程度春季高于秋季。典范对应分析发现秋季TN(F=3.25,P=0.012)和水温(F=2.86,P=0.016)为显著影响鱼类群落的环境因子。     

雅砻江中下游鱼类栖息地评价与保护方案

采用Barbour（1996）提出的栖息地评价指标体系，由底质、栖息地复杂性、流速和水深结合特性、堤岸稳定性、河道变化、河水水量状况、植被多样性、水质状况、人类活动强度和河岸土地利用类型共计10项指标构成雅砻江中下游鱼类栖息地评价指标体系，并依之对雅砻江中下游干流及其主要支流共985 km江段的鱼类栖息地进行了评价。评价结果是无“较差”河流；卧龙寺沟为“一般”； 达曲河为“较好”；其他河流“好”。基于此结果，建议雅砻江中下游按照“两区一段”和局部水域进行栖息地保护，将两河口库尾3.9 km保留河段、34.8 km变动回水区域、支流曲入河作为中游高原鱼类栖息地保护水域，将桐子林坝下及邻近水域作为雅砻江汇口栖息地保护水域，将锦屏二级闸厂址119.0 km大河湾段作为下游东部江河平原鱼类大河湾保护水域。局部水域主要指鳡鱼河支库及其源头支流永兴河、惠民河、达曲河、力丘河、色物绒沟。针对不同河段的保护功能与鱼类栖息地现状，提出了开展相关研究、监测和生态修复等对策的建议。     

新疆博尔塔拉河冬季鱼类群落空间分布及其与环境因子的关系

为完善新疆博尔塔拉河流域的渔业生态评估及体系养护,2016年11月在博尔塔拉河流域展开资源调查,于干流设置4个监测断面,对该水域鱼类群落结构进行研究。本调查共采集鱼类1515尾,隶属于3目5科14属,共计15种,均为硬骨鱼类;通过相对重要性指数(IRI指数)获得的博尔塔拉河干流的鱼类优势种共计3种,分别为麦穗鱼(Pseudorasbora parva)、棒花鱼(Abbottina rivularis)和新疆高原鳅(Triplophysastrauchii)。基于Bray-Curtis相似性指数的二维聚类分析结果显示,在60%相似水平上空间聚类,可将博尔塔拉河分为上游及下游2组,物种聚类在50%相似水平上可分为Ⅰ～Ⅳ共计4组。典范对应分析(CCA)表明,影响冬季鱼类群落空间结构的主要环境因子为海拔、温度和溶氧。对照历史资料结果表明,博尔塔拉河流域的土著鱼类种类减少;外来鱼类种类逐年增加;经济鱼种减少;鱼类群落小型化明显。本研究可为该流域生态环境评估、水资源开发利用及渔业资源养护提供基础数据,具有一定的参考价值。     

长江口青草沙水库正式供水前的鱼类群落结构特征

为研究上海青草沙水库的鱼类物种组成、多样性及其空间变化,2010年7--10月在该水库共捕获鱼类993尾,隶属5目,18种,其中淡水鲤形目鱼类最多,占总物种数的72.2％.群落优势种为贝氏(鳖)、刀鲚、鲫、光泽黄颡鱼.聚类分析表明,鱼类群落类型存在较显著的空间差异,刺网网目大小对渔获物物种组成有较显著的影响.物种多样性与丰富度和均匀度均显著正相关,但更多地受丰富度的影响.单因素方差分析表明,鱼类物种多样性在空间上无显著差异.4种摄食功能群中,无脊椎动物食性(44.4％)和杂食性(33.3％)鱼类物种数比例较高；4种生态类群中,定居性鱼类占绝对优势(77.8％).青草沙水库鱼类群落表现出淡水或长江口低盐淡水区鱼类区系的主要特征,与以近海鲈形目鱼类为优势的长江口邻近水域的鱼类群落差异巨大,推测水库建设导致的隔离与盐度下降是形成该水库鱼类群落趋于淡水区系的主要原因.     

乐清湾口海域春秋季鱼类群落多样性研究

为研究乐清湾口海域鱼类群落结构动态变化趋势和渔业资源现状,对该海域鱼类物种组成、种类数、多样性等群落结构特征进行调查分析。共鉴定出鱼类49种,隶属于10目26科39属。结果显示,春季物种数较秋季少,春季在瓯江口水域物种明显较少,秋季物种数空间分布大致为东西走向;春季种类重量多样性低于秋季,但尾数多样性高于秋季,鱼类种类数与多样性指数之间有较强的相关性。研究表明,乐清湾口海域的鱼类种类类型以近岸河口性鱼类为主,且大多为广温、广盐性种类;该海域位于河口,受瓯江径流影响较大;受地理位置和水文环境影响,该海域暖水性种类较多;种类数平面分布特征主要是春季受瓯江径流淡水水团影响,而秋季受交汇水团影响,物种丰富;两季鱼类多样性不同,是因为鱼类个体大小、数量随着季节的变化而变化。     

金沙江旭龙水电站鱼类栖息地适宜性评价

为筛选金沙江上游旭龙江段鱼类栖息地保护支流，从替代适宜性和保护适宜性两个角度构建了鱼类栖息地适宜性评价指标体系，选取了11个与栖息地质量密切相关的评价指标，应用层次分析法确定评价指标的权重值，计算了三条主要支流的栖息地适宜性指数（HSI），并划分了栖息地适宜性等级。结果表明：重点保护鱼类物种相似性、纵向连通性指数、特有鱼类物种相似性3项指标的权重值位列前三位，分别为0.234、0.234、0.127；定曲、麦曲河、丹达曲的HSI 分别为84.1、72.0和61.3，定曲适宜性等级最高为“高度适宜”，麦曲河、丹达曲适宜性等级为“适宜”。针对当前定曲鱼类生境存在的问题，拟定了补建过鱼设施、开展受损河道生境修复、实施生态调度以及加强水污染监管等对策措施，以期为受水电开发影响下的河流栖息地筛选与保护提供参考。     

蓄水运行时长对鱼类群落结构及生态类型的影响——以乌江下游银盘电站为例

为研究梯级电站修建及运行不同阶段导致的河流生境变化对鱼类群落结构和生态类型的影响,本研究于2005-2017年间在乌江下游银盘电站坝上坝下江段开展了蓄水前（2005、2008-2009年）、蓄水后两年内（2011-2012）蓄水6年后（2017年）共6个年度鱼类资源监测,采用多样性指数和多元统计方法分析了该江段鱼类种类组成、群落结构特征及其变化。6年共监测到鱼类93种,鱼类种类数随蓄水进行呈现先降低后升高的趋势。受生境变化影响,鱼类优势物种发生变化,电站蓄水前后差异较大,特别是蓄水后两年内差异尤其显著。蓄水前后鱼类群落结构也发生了变化,在61.79%的Bray-Curtis相似性水平上,蓄水前鱼类聚为一组,蓄水后两年内鱼类聚为一组,2017年单独一组,在0.05水平上差异显著。总体上看,生态类型组成上以缓流型、底层、定居性、杂食性和产粘性卵鱼类占优;蓄水后两年内中上层鱼类和静水型鱼类个体数占比显著增大。     

广西会仙湿地农田沟渠鱼类群聚差异研究

研究会仙湿地非硬质化、半硬质化和硬质化沟渠中夏秋两季鱼类组成，评价沟渠硬质化对鱼类生物多样性影响。采用电捕法和人工抄网共采集鱼类标本1388尾，经鉴定为25种，隶属于5目10科22属。单因素方差分析（ANOVA）结果显示夏季非硬质化沟渠的鱼类Shannon-Wiener指数显著高于硬质化沟渠（P＜0.05）；秋季非硬质化沟渠及半硬质化沟渠的鱼类生物量显著高于硬质化沟渠（P＜0.05）；秋季半硬质化沟渠的鱼类个体数显著高于硬质化沟渠（P＜0.05）；夏季非硬质化沟渠的鱼类物种数显著高于硬质化沟渠（P＜0.05），而秋季半硬质化沟渠的物种数显著高于硬质化沟渠（P＜0.05）。鱼类群落多维排序图（NMDS）结果显示，夏秋两季鱼类群落结构基本能分开，且鱼类群落结构的相似性分析(ANOSIM)显示夏秋季之间的鱼类群落结构存在显著差异（P＜0.05）；鱼类群落NMDS排序与单因子相似性分析结果显示，夏季和秋季会仙湿地农田3类沟渠的鱼类群落结构均无显著差异（P＞0.05）。     

禁捕初期长江下游鱼类群落现状分析及禁渔效果初步评估

为了解禁捕初期长江下游鱼类群落结构特征，实验于2021年春季、夏季、秋季和冬季对长江下游鱼类群落进行4次调查。结果显示，实验共采集鉴定鱼类84种，分属10目18科63属，其中47.62%为鲤科鱼类。以物种数和多样性指数分析群落多样性特征，结果表明长江下游鱼类多样性水平较高，但鱼类种类较历史记录偏少。单因素方差结果显示，鱼类种类数、种群数量和重量空间差异显著，季节差异不明显。群落优势种为光泽黄颡鱼、鳊、鲢、短颌鲚、贝氏?等9种。4种摄食功能群中，肉食性(47.62%)和杂食性(40.47%)鱼类物种比例较高；洄游习性方面，淡水定居性鱼类占绝对优势(76.19%);3种栖息水层类型中，底层鱼类物种数比例较高(46.43%)。大型经济鱼类占总量比例低，但个体相对较大，因而相对重要性指数(IRI)更高。长江下游鱼类多样性指数为3.28，水域鱼类多样性水平较高。长江下游鱼类个体小型化、低龄化现象依然存在，长江十年禁渔实施后，禁渔效果初步显现，鱼类物种数、多样性指数和单位捕捞努力量渔获量均有所增加。建议进一步加强禁捕期科研监测，加大监管力度，保障长江下游鱼类资源得以有效恢复，巩固禁捕成效。本研究可...     

Influences of local habitat and stream spatial position on fish assemblages in a dammed watershed,the Qingyi Stream,China

Abstract – Identifying the underlying mechanisms that explain the spatial variation in stream fish assemblages is crucial for the protection of species diversity. The influences of local habitat and stream spatial position on fish assemblages were examined from first‐order through third‐order streams within a dammed watershed, the Qingyi Stream, China. Based on linear regression models, the most important environmental variables influencing fish species richness were water temperature and wetted width, but stream spatial position variables were less important. Using canonical correspondence analysis, five environmental variables were identified to significantly influence fish assemblages, including three habitats (elevation, substrate and water depth) and two spatial variables (C‐link and Link). Our results suggest that, in a heavily dammed watershed, by blocking the migration routes of fishes, dams weaken the influence of stream spatial position on fish species richness. However, fish species compositions are significantly influenced by both local habitat environment and stream spatial position, which is perhaps owing to the distribution of fish species according to ecological requirements not related to spatial processes.     

Effects of within-patch habitat structure and variation on fish assemblage characteristics in the Bernecei stream, Hungary

Abstract –  Over a 3-year period we examined variability in physical habitat structure and species richness, abundance and assemblage composition of fishes in 13 habitat patches in the Bernecei stream, Hungary. Principal component analysis of habitat structure data from patches elucidated a riffle-run-pool habitat gradient across patches. Temporal habitat variability increased significantly from riffle to pool patches. Fish assemblage characteristics displayed relatively continuous change over the habitat gradient and were relatively stable within patches. Assemblage structure properties (e.g., species richness) displayed different responses to the habitat gradient and to within-patch habitat variability. In general, pool patches had more diverse assemblages and greater within-patch assemblage variability than riffle patches. However, within-patch dynamics were largely determined by the population dynamics of a habitat generalist (i.e., minnow). Broad scale environmental variability (i.e., a catastrophic 100-year flood) also appeared to affect within-patch fish assemblage characteristics. Our results demonstrate that fish assemblage structure is influenced by physical variability (i.e., both floods and spatio-temporal habitat variability) within the Bernecei stream.     

Fish assemblages structure and function along environmental gradients in rivers of Gabon (Africa)

Abstract –  We examined patterns in fish species assemblages structure and function along environmental gradients in rivers of Gabon. Species presence–absence data from 52 sites were first analysed by canonical correspondence analysis. Results showed that the position of sites along the upstream–downstream gradient, together with elevation and water conductance were the most important predictors of local fish assemblage composition. Assemblage richness and trophic structure were further investigated using regression tree analysis. Results revealed a general increase in species richness from upstream to downstream areas and a transition from insectivorous to omnivorous, herbivorous and piscivorous species along this longitudinal gradient. There were several similarities between these previous patterns and those observed in other temperate streams suggesting a potential convergence in fish assemblage along environmental gradients in tropical and temperate riverine systems. From a conservation standpoint, these results highlight the need to evaluate all habitat types along rivers longitudinal gradient to integrate the full spectrum of species assemblages within conservation plans.     

Land cover,riparian zones and instream habitat influence stream fish assemblages in the eastern Amazon

The Amazon rainforest has experienced rapid land‐use changes over the last few decades, including extensive deforestation that can affect riparian habitats and streams. The aim of this study was to assess responses of stream fish assemblages to deforestation and land cover change in the eastern Amazon. We expected that percentage of forest in the catchment is correlated with local habitat complexity, which in turn determines fish assemblage composition and structure. We sampled 71 streams in areas with different land uses and tested for relationships between stream fish assemblages and local habitat and landscape variables while controlling for the effect of intersite distance. Fish assemblage composition and structure were correlated with forest coverage, but local habitat variables explained more of the variation in both assemblage composition and structure than landscape variables. Intersite distance contributed to variance explained by local habitat and landscape variables, and the percentage of variance explained by the unique contribution of local habitat was approximately equivalent to the shared variance explained by all three factors in the model. In these streams of the eastern Amazon, fish assemblages were most strongly influenced by features of instream and riparian habitats, yet indirect effects of deforestation on fish assemblage composition and structure were observed even though intact riparian zones were present at most sites. Long‐term monitoring of the hydrographic basin, instream habitat and aquatic fauna is needed to test for potential legacy effects and time lags, as well as assess species responses to continuing deforestation and land‐use changes in the Amazon.     

Effects of an extreme flash flood on the native fish assemblages across a Mediterranean catchment

Abstract  The effects of an extreme flash flood on the native fish assemblages across a Mediterranean catchment in Southwest Portugal were investigated. The fish community structure and habitat were surveyed at 10 sites pre- and post-flood. Overall species richness and rank abundances changed little after the flood, despite there being a consistent decline in the abundance of small cyprinids. Pre- and post-flood habitat correlates of abundance changed for at least some species, and variability in assemblage structure was associated with flood, depth and pH. These results indicate that extreme floods occurring early in the wet season may have little disruptive effects on the overall structure of native fish assemblages in Mediterranean streams, although may at least partially influence population dynamics for some species. Habitat quality and complexity are likely to play a role in mediating species responses to flooding.     

Multiple watershed alterations influence fish community structure in Great Plains prairie streams

Stream fish distributions are commonly linked to environmental disturbances affecting terrestrial landscapes. In Great Plains prairie streams, the independent and interactive effects of watershed impoundments and land cover changes remain poorly understood despite their prevalence and assumed contribution to declining stream fish diversity. We used structural equation models and fish community samples from third‐order streams in the Kansas River and Arkansas River basins of Kansas, USA to test the simultaneous effects of geographic location, terrestrial landscape alteration, watershed impoundments and local habitat on species richness for stream‐associated and impoundment‐associated habitat guilds. Watershed impoundment density increased from west to east in both basins, while per cent altered terrestrial landscape (urbanisation + row‐crop agriculture) averaged ~50% in the west, declined throughout the Flint Hills ecoregion and increased (Kansas River basin ~80%) or decreased (Arkansas River basin ~30%) to the east. Geographic location had the strongest effect on richness for both guilds across basins, supporting known zoogeography patterns. In addition to location, impoundment species richness was positively correlated with local habitat in both basins; whereas stream‐species richness was negatively correlated with landscape alterations (Kansas River basin) or landscape alterations and watershed impoundments (Arkansas River basin). These findings suggest that convergences in the relative proportions of impoundment and stream species (i.e., community structure) in the eastern extent of both basins are related to positive effects of increased habitat opportunities for impoundment species and negative effects caused by landscape alterations (Kansas River basin) or landscape alterations plus watershed impoundments (Arkansas River basin) for stream species.     

Fish species incidence patterns in naturally fragmented Chihuahuan Desert streams

We investigated how stream fragmentation affects local fish species persistence and extinction from three Rio Grande systems (Texas, USA) stream reaches with different levels of natural fragmentation. We examined species–volume (SV) relationships of fish assemblages in 42 pools across the watersheds and predicted greater fragmentation would correspond to an increase in the slope of the SV relationship due to decreased within‐reach rescue effects. In addition, we examined relationships among tributary‐specific nested subset patterns, local habitat features and spatial position of the reaches relative to the Rio Grande mainstem to better understand the importance of local and regional processes on fish species richness patterns in the stream reaches. Slopes of the SV curves did not differ among the stream reaches, but the intercepts of the SV curves were significantly different. These results indicated rescue effects among habitats within a stream reach were not apparent; however, rescue effects from the mainstem largely determined the species richness of a given stream reach. The nested subset patterns in all stream reaches were related to several local environmental factors, and large, deep pools provided important aquatic refugia in all three systems. We suggest declines in mainstem and tributary flows will likely continue to impact local and regional fish assemblage attributes. High flow events are important for dispersal and can reset tributary fish communities for the next extinction‐driven, successional cycle.     

Fish assemblages in Atlantic Forest streams: the relative influence of local and catchment environments on taxonomic and functional species

Streams are under environmental pressures acting at different scales that influence the ecological organisation of their fish assemblages. However, the relative influence of the different scale‐related variables on assemblage composition and function is poorly understood. We evaluated the importance of local‐ and catchment‐scale environmental variables, as well as the spatial structure of the sampling sites, in shaping fish assemblages in Atlantic Forest streams. Local‐scale variables were those measured at the sampling sites, describing the local habitat conditions (e.g. depth, substrate type, altitude). Catchment‐scale variables were those integrating the upstream landscape of the sampling sites (e.g. catchment land use). Spatial distances were calculated from watercourse distance using principal coordinates of neighbour matrices. Altogether, 28 local and seven catchment variables were initially subjected to two processes of eliminating co‐linearity. Redundancy analysis was applied to the three matrices (spatial, local and catchment) to quantify the variance in the structure of the fish assemblages explained by each matrix. Local variables explained more variability in both taxonomic and functional assemblage structure, than catchment and spatial variables. Local variables also changed along the longitudinal gradient, which consequently influenced fish assemblage structure. This pattern was also influenced by anthropogenic alteration and non‐native species, which were more abundant in downstream sites. These results highlight the need to assess Atlantic Forest streams under different environmental scales, especially through the use of quantitative local‐scale metrics, and to consider the effects of longitudinal patterns in structuring fish assemblages when developing and implementing monitoring programmes, impact studies and conservation plans.     

Habitat relationships with fish assemblages in minimally disturbed Great Plains regions

Abstract – Effects of local environmental influences on the structure of fish assemblages were evaluated from 159 sites in two regions of the Great Plains with limited anthropogenic disturbance. These regions offered an opportunity to evaluate the structure and variation of streams and fish assemblages within the Great Plains. We used canonical correspondence analyses to determine the influence of environmental conditions on species abundances, species occurrences and assemblage characteristics. Analysis of regions separately indicated that similar environmental factors structured streams and fish assemblages, despite differences in environmental conditions and species composition between regions. Variance in fish abundance and assemblage characteristics from both regions was best explained by metrics of stream size and associated metrics (width, depth, conductivity and instream cover). Our results provide a framework and reference for conditions and assemblage structure in North American prairie streams.     

Relative importance of local and landscape variables on fish assemblages in streams of Brazilian savanna

Understanding variability in the composition of aquatic assemblages requires a multiscale perspective, since processes operating at different spatial scales (from regional to local) drive the community assembly. Here, the relative importance of environmental variables on fish species composition in streams of the Brazilian savanna (Cerrado) is assessed and quantified at local and landscape scales. The importance of both local and landscape environmental variables in structuring fish assemblages was supported. Local variables explained a substantially higher amount of variance of fish assemblages than landscape variables. However, the shared explanation indicate that landscape variables had a complementary effect. The streams sampled were mostly headwaters at similar altitudes and with similar watershed sizes, so the sensitivity of the fish assemblages, even to small landscape gradients, is highlighted. Maintaining these important instream habitat characteristics close to natural conditions seems to be essential for conserving stream fish species, and for this, the landscape context should be taken into account. Considering the near‐pristine condition of the streams studied, these findings can be used as a reference for further studies addressing the effects of human modifications on stream fish biodiversity of the Cerrado.