天然河道中鱼类对水深、流速选择特性的初步观测——以长江江口至涴市段为例

将长江江口至涴市天然河道的鱼类水声学调查数据和水文学观测数据相结合,在对流速和水深空间插值基础上,提取不同鱼类规格和密度对应水深和流速的特征值,从而研究鱼类对天然河道中水层平均流速、水深2个环境因子的选择特性。研究结果表明：①不同规格的鱼对流速和水深的选择存在差异,规格小的鱼选择了较低的流速和较宽的流速范围,规格大的鱼选择了较高的流速和较窄的流速范围;规格小的鱼选择的水深明显高于规格大的鱼,喜好的水深范围也宽于规格大的鱼。②鱼类密度对流速的选择性不明显,但对水深的选择性明显,即深水区鱼类密度较高。③研究江段范围内江口镇附近江心洲两侧流速变幅范围较其上、下游江段宽,并且江心洲两侧鱼类的分布密度也高于其邻近上、下游段鱼类密度。可见,江心洲的存在提供了流速多样性格局,丰富了鱼类生境的多样性。本研究方法可为评价河流栖息地适宜性及生态功能提供借鉴。     

基于模糊逻辑的裂腹鱼幼鱼生境适宜度指数分析

通过模糊逻辑的方法建立了雅砻江裂腹鱼幼鱼时期的生境适宜度指数模型。根据野外调查和室内实验结果,结合有经验的鱼类学专家的模糊知识建立了关于生境因子和幼鱼生境适宜度模糊集合的隶属度函数和模糊推理规则。模糊集合根据水温、流速和溶解氧3个变量因子,以“if-then”的规则语句实现了生境特性和适宜度的联系。根据模型分析,得出溶解氧是裂腹鱼幼鱼重要的生境因子,其次是温度和流速。单因子变化引起的相对极端环境对鱼类适宜度有显著影响。裂腹鱼对水温、溶解氧和流速的最适范围分别为11 ℃~19 ℃,5.75~10 mg/L和0.1~0.65 m/s。     

草鱼幼鱼游泳能力及游泳行为试验研究

在28±1℃水温下,利用自制鱼类游泳行为试验装置,采用流速递增法,研究了体长5.0~15.0 cm草鱼幼鱼的游泳能力和游泳行为。结果表明:该体长范围内的草鱼幼鱼临界游速在68~100 cm/s之间,临界游速基本随鱼类体长增加而线性增长;在整个试验过程中,根据鱼类对水流流速的游泳行为响应,鱼类的摆尾频率随着水流速度的增加而线性增加,整个游泳过程分为4个阶段,每个游泳阶段的最大流速依次为临界游速的45.6%、82.8%、95.9%和100%。本研究成果可为四大家鱼游泳能力进行有益补充,也可为鱼道流速设计提供游泳能力参数。     

基于数值模拟的清泥河鱼类水力生境评价

以清泥河生态修复重要节点双龙湖为模拟区域,建立了二维水动力模型,选取重现期10 a的洪水过程线为上游流量入流边界,模拟了双龙湖在该过程下的流场情况。根据《清泥河水生态状况调查研究报告》,以子陵吻■虎鱼为评价对象,以流速与水深为评价指标,利用模糊综合评价方法评价了双龙湖在洪水历时为0%、6%、12%、24%、48%时刻的水力生境适宜性,通过分析可知子陵吻■虎鱼适宜流量为59.70 m~3/s,在该流量下区域水力生境适应性程度最高。     

汉江桥闸工程下游河段典型鱼种栖息地模拟研究

探究水利工程干扰下的鱼类生境变化特征是维护河流生态健康的基础性研究。以汉中平川段内汉江三桥桥闸下游10 km为研究河段,利用水文学法和栖息地模拟法计算了生态流量。建立了河段二维水动力学模型,选用宽鳍鱲为目标鱼种,依据其对水深和流速的适宜性曲线确定了流量变化下的生境面积,并采用生境质量分级分析了不同流量响应鱼类生境的变化特征。研究结果表明:两种方法计算出河流生态流量相近,分别为54.3和53.1m~3/s,最终适宜流量为47.8～54.3 m~3/s;在流量8.8～212.7 m~3/s时,相比中等和低质量生境,高质量生境面积随流量的波动更为显著,呈现先升后降的趋势,212.7 m~3/s以上流量的各级生境面积随流量变化较小;高质量生境多分布于两岸和冷水河交汇口,中等质量生境主要分布在河段下游;低质量生境位置相对不固定;研究成果可为桥闸运行和河流鱼类保护提供重要参考依据。     

三峡水库变动回水区蓄水期鱼群空间分布及生境特征

三峡水库蓄水后变动回水区水动力条件和泥沙运动发生了显著变化,鱼类栖息地也受到了不同程度的影响。为了掌握三峡变动回水区朝天门至涪陵河段蓄水期鱼类栖息地现状,研究采用Bisonics DT-X科学回声鱼测仪对朝天门至涪陵河段进行了鱼群空间分布及生境特征监测。结果表明:蓄水期该河段水环境因子空间分布变化不显著,表明水环境因子不是影响该河段鱼群分布的主要原因;水深与流速在该河段变化较大,是影响鱼类栖息的关键因子;监测到8个大型鱼群平均密度为(64.6±13.5) ind/(10³ m³),鱼类平均体长为(16.8±4.6 )cm,以中小型鱼为主;回水沱、深潭及分汊河道是鱼类喜居河段,是鱼类重要栖息地。研究结果可为三峡水库变动回水区鱼类保护和栖息地修复提供科学依据。     

与鱼道水力设计相关的草鱼幼鱼游泳行为特性研究

在25±0.5℃水温条件下,针对体长在5.0~16.0 cm范围内的草鱼幼鱼,利用鱼类游泳行为测试水槽研究了与鱼道水力设计密切相关的草鱼幼鱼游泳特性指标和游泳行为,结果表明该体长范围的草鱼幼鱼平均感应流速为12.84 cm/s,突进游泳速度随着体长增加而线性增加,相对突进游速随着体长增加而线性减小,突进游速约为临界游速的1.05~1.28倍,而且鱼体越长,突进游速超出临界游速就越多。在突进游速试验过程中分析了流速快速变化对鱼类游泳行为的影响,发现试验鱼在适应流速变化过程中,顺流而下、逆流静止、逆流冲刺、逆流后退4种游泳行为相互穿插,并根据鱼类游泳状态的变化,将整个流速递增的游泳过程分为4个阶段,提出以草鱼为过鱼对象的鱼道池室主流最大流速不宜超过第1阶段的最大流速(草鱼幼鱼突进游速的52%~60%),对于竖缝、孔口等鱼道的高流速区,其最佳流速不应高于第2阶段的最大流速(突进游速的76%~79%),绝不可超过第3阶段的最大流速(突进游速的90%~96%)。研究成果补充了四大家鱼游泳特性指标,可为鱼道设计提供水力设计参数。     

基于物理栖息地模拟的长江中游生态流量研究

将Delft3D水力学模型和栖息地模型组成物理栖息地模拟模型以研究鱼类的生态环境。以长江中游宜昌至枝江河段为研究区域,以长江的重要经济鱼类四大家鱼为目标物种,结合流速及水深两个栖息地限制因子计算研究区域内不同流量下四大家鱼4个产卵场的栖息地面积,得到了流量与栖息地面积关系曲线。分析该曲线,结果表明：长江中游四大家鱼4—6月份产卵期间的最小生态流量为4 570m3/s,适宜生态流量范围为12 000~15 500m3/s。计算结果在传统水文学法界定的生态流量范围之内,分析认为该计算结果更加合理,可为四大家鱼的保护和三峡及葛洲坝工程的生态调度提供参考建议。     

同侧竖缝式鱼道结构优化数值模拟研究

鱼道是保证鱼类能顺利洄游的过鱼设施。通过竖缝相对宽度分别为0.05,0.10,0.15,0.30,底坡为10%的鱼道模型进行数值计算。采用可视化显示及数据分析的方法分析不同竖缝相对宽度、底坡条件下的同侧竖缝式鱼道的水流结构特征。通过模型模拟,分析水流沿水深方向的流速分布情况、主流区最大流速沿程分布及沿程衰减情况,以及在不同竖缝相对宽度和(或)不同流速情况下的紊动能分布情况。综合各物理量的分析,得出竖缝相对宽度b₀/B=0.15、底坡为10%时,水流在池室内能形成较好的适合鱼类洄游的流态:主流区水流横向扩散范围适中,主流区最大流速沿程均匀衰减,回流区面积较为对称,流速较小。     

海河流域河道最小生态流量研究

应用基于河流形态的河道最小生态流量计算方法,选取潘家口、滦县、石匣里、官厅、观台、楚旺及称钩湾7个控制断面对海河流域河道最小生态流量进行计算.该方法立足河流形态,将水位水面宽曲线突变点与维持一定生境(主要包括平均水深、流速等)综合考虑来确定临界流量.计算结果表明:7个控制断面的最小生态流量均值为5.84 m3/s,占多年平均流量的5.8%~10%;在最小生态流量下的水面宽率为43%~70%(平均为61%),平均水深为0.24~0.59 m,流速为0.24~0.34 m/s.这些计算结果与国际上已有的计算结果相符.根据流域相似性原理进行外推,计算了海河流域其他河道的最小生态流量.     

Assessing habitat for lake sturgeon (Acipenser fulvescens) reintroduction to the Maumee River,Ohio using habitat suitability index models

Lake sturgeon (Acipenser fulvescens) were a candidate for reintroduction in the Maumee River, Ohio, where they were historically abundant, but are now functionally extirpated. Our objective was to determine if current habitat quality and quantity could support reintroduction efforts. We developed a spatially explicit habitat suitability index model for two lake sturgeon life stages: spawning adult and age-0 fish. To estimate habitat quality, substrate, water depth, and water velocity were assessed and integrated into suitability index values to delineate good, moderate, and poor areas for each life stage. Each habitat characteristic was mapped and combined to provide an overall assessment of habitat suitability, quantity, and location. Model results indicated 208 ha (10.2% of all habitat) of good adult spawning habitat (e.g., coarse substrates, depths between 0.3 and 8 m, and velocity between 0.5 and 1 m/s) and 529 ha (28.2% of all habitat) of good age-0 habitat (e.g., fine substrates, depths between 0.2 and 6 m, and velocity between 0.1 and 0.7 m/s). Good age-0 habitat was located mostly downstream of good spawning habitat, which will provide nursery areas for age-0 fish after hatch. Our models suggested habitat is not limiting for lake sturgeon and efforts to reintroduce this species into the Maumee River, and for the first time in the Lake Erie basin, were supported. The results of this work supported reintroduction efforts that began in 2018.     

Evaluation of fish habitat suitability using a coupled ecohydraulic model: Habitat model selection and prediction

The selection of an approach to evaluate habitat suitability for a specific fish or life stage has been a matter of concern in habitat quality modelling studies. This study has taken Jinshaia sinensis, a commercially valuable fish endemic to the Jinsha River, China, as the target fish species. One‐ and two‐dimensional hydrodynamic models were coupled and combined with fish habitat models for a middle reach of the Jinsha River. The resulting ecohydraulic model was used to predict the changes in hydrodynamics and spawning habitat suitability that resulted from the operation of an under‐construction reservoir downstream of the study area. The preference function (product, arithmetic mean, geometric mean, and minimum value) and fuzzy logic habitat evaluation methods were compared to predict the spawning habitat suitability of the fish. The model was validated using the numbers of spawning eggs, and the results show that both the arithmetic mean and fuzzy logic method can be used to predict spawning habitat suitability. The model predictions show that the hydrodynamics of the study area would be altered if the impoundment water level exceeded 969 m. During the spawning season, the spawning habitat suitability would increase from April to early June and has little change from early June to July under the impact of the reservoir impoundment. The optimal river discharge rate for fish spawning is ~3,500 m³/s, and this would not change after the reservoir begins operation. This research can benefit other regions that will be affected by planned dams by predicting the impacts of reservoir operation on fish habitat quality, and the results will help decision makers protect the health of rivers and the overall ecosystem.     

Development of habitat suitability criteria for trout in small streams

We observed 2863 trout in the wild to determine habitat utilization in small streams of the Kings River basin in California's Sierra Nevada mountains. The habitat utilization data were used to develop habitat suitability functions that provide input variables to the instream flow incremental methodology (IFIM) habitat assessment model of the U.S. Fish and Wildlife Service. Observations of habitat utilization of rainbow trout (Salmo gairdneri), brown trout (Salmo trutta), and brook trout (Salvelinus fontinalis) were obtained during the summer months of 1983 and 1984. The observations were made in small streams with discharges ranging from 0.7 m³ s^?1 to 0.03 m³ s^?1. The streams are at elevations of 1250 to 2530 m. Equal effort was applied to observing undisturbed trout in all habitat types. Snorkeling proved to be the most effective method of observation. Individual trout of all species and life stages were most often observed in the lower half of the water column, utilizing low-velocity currents of less than 3.0 cm s^?1. From the depth and velocity utilization data, several forms of habitat suitability functions were developed and evaluated:

• 1 Univariate depth and velocity functions derived from frequency histogram analysis.
• 2 Univariate depth and univariate velocity exponential polynomial models.
• 3 Bivariate depth and velocity exponential polynomial models.

Univariate exponential polynomial models provided the best fit to the data for each species, based on visual comparisons of response surfaces and contour plots, and comparisons of computed sums of squared errors. Bivariate models fitted to the data resulted in greater sums of squared errors than multiplicative aggragation of univariate models, and frequently predicted utilization at zero depth. The habitat suitability functions derived from the univariate exponential polynomial models provided the best input to the IFIM habitat assessment models.     

A probability-based model to quantify the impact of hydropeaking on habitat suitability in rivers

A negative effect of hydropower on river environment includes rapid changes in flow and habitat conditions. Any sudden flow change could force fish to move towards a refuge area in a short period of time, causing serious disturbances in the life cycle of the fish. A probability-based model was developed to quantify the impact of hydropeaking on habitat suitability for two fish species, brown trout (Salamo trutta) and Grayling (Thymallus thymallus). The model used habitat preference curves, river velocity and depth to develop the suitability maps. The suitability maps reveal that habitat suitability deteriorates as flow increases in the studied part of the river. The probability model showed that, on average, suitability indices are higher for adult grayling than juvenile trout in hydropeaking events in this part of the river. The method developed shows the potential to be used in river management and the evaluation of hydropeaking impacts in river systems affected by hydropower.     

Habitat suitability of golden mahseer young ones (Tor putitora,Hamilton 1822) in Himalayan waters,India

Habitat suitability refers to the mechanism that enables organisms to choose suitable habitats to survive. In the present study, we studied the habitat suitability of young golden mahseer (fingerlings and juveniles) in the streams of the Ramganga River, one of the prominent rivers of the western Himalaya. Different habitat types and microhabitat features were documented. Habitat suitability was evaluated by generating habitat suitability criteria curves in response to varying habitat availability and use by young golden mahseer during different seasons. Generalised linear modelling (GLM) was used to analyse environmental characteristics responsible for selecting golden mahseer habitats. We studied mahseer based on body size into two main classes, that is, fingerlings (1.5–10 cm) and juveniles (10–30 cm). Golden mahseer fingerlings preferred mean depth (0.1–0.6 m) and mean stream velocity (0–0.2 m/s) at stream reach dominated by diverse substrate compositions such as sand, gravel, and small cobbles. Similarly, juveniles preferred mean depth (0.1–1.5 m) and mean water velocity (0.1–0.5 m/s), with cobbles, bedrock, and sand dominating their habitats. The GLM results indicated that dissolved oxygen, temperature, and water velocity were the significant factors influencing habitat suitability. High dissolved oxygen positively influenced fingerlings, whereas moderate to high water velocity affected juveniles the most. Therefore, to understand the flow requirement for threatened species like golden mahseer, it is essential to characterise critical habitats and develop criteria based on habitat suitability curves.     

浅水湖泊底栖动物栖息地模拟

为研究白洋淀水生生物栖息地适宜度,分别于2016年春、夏、秋3季进行了实地考察和采样,结合野外观测和实验室测量得到环境和生物信息。基于14个采样点的数据,通过构建广义可加模型(GAMs)模拟和预测底栖动物的分布。使用Margalef指数作为响应变量,采用向前逐步回归筛选解释环境因子,通过评价剩余偏差来判断模型的表现。水深、水温、底泥氨氮、底泥有机质和沉水植物生物量被用于建立最终优化的广义可加模型。Margalef指数对环境因子的响应曲线表明该指数与水深和底泥氨氮浓度成线性负相关,与水温和底泥有机质浓度成线性正相关,而与沉水植物生物量是单峰关系。结果表明,预测值与实测值呈现显著的强相关性(Pearson R~2=0.847,P0.001),均方误差较小(MSE=0.013),模型性能表现良好。     

Comparison of approaches for modelling submerged aquatic vegetation in the Toronto and Region Area of Concern

In freshwater aquatic ecosystems, submerged aquatic vegetation (SAV) is critical habitat for may fish species and provides a variety of ecosystem services including nutrient filtration and substrate stabilization. Characterizing habitats and assessing their suitability for fish and other aquatic and terrestrial organisms is an important component of delisting efforts in the Toronto and Region Area of Concern (AOC). The primary objective of this study was to develop a spatial model for SAV within the AOC. A variety of modelling options were explored with a two stage random forest model identified as the most accurate approach; a two stage boosted regression tree model yielded comparable accuracy but was more complicated and processing intensive to implement. The final models for presence (modelled first) and SAV percent cover (applied only where the presence model predicted SAV to occur) incorporated directionally weighted wind fetch, water depth, and clarity (Secchi depth) with relatively high predictive accuracy (87.1% for presence). When applied across the AOC, SAV was primarily found to occur within the Central Waterfront, particularly adjacent to and among the Toronto Islands. Outside of this area, SAV was generally sparse and confined to areas that were protected from wind and wave action from Lake Ontario. Future habitat creation and remediation efforts should therefore focus on creating habitat conducive to SAV establishment.     

Using habitat guilds to develop habitat suitability criteria for a warmwater stream fish assemblage

The diversity of fish species found in warmwater stream systems provides a perplexing challenge when selecting species for assessment of instream flow needs from physical habitat analyses. In this paper we examined the feasibility of developing habitat suitability criteria (HSC) for the entire fish community of a warmwater stream using habitat guilds. Each species was placed a priori into a guild structure and habitat data were collected for depth, velocity, Froude number, distance to cover, embeddedness and dominant and subdominant substrate. Correct guild classification was tested with linear discriminant analysis for each species. Correct classification based on habitat‐use data was highest for riffle and pool‐cover guilds, whereas the fast‐generalist and pool‐run classes, the broader niche guilds, were more frequently misclassified. Variables most important for discriminating guilds were Froude number, velocity and depth in that order. Nonparametric tolerance limits were used to develop guild suitability criteria for continuous variables and the Strauss linear index was used for categorical variables. We recommend the use of a wide array of variables to establish more accurate habitat analysis. Additionally, guild HSC can be developed with similar effort to that needed to develop HSC for a small number of individual species. Results indicate that a habitat guild structure can be successfully transferred to another river basin and that habitats for a diverse fish assemblage can be adequately described by a small number of habitat guilds. This approach represents an alternative for incorporating entire fish assemblages into habitat analyses of warmwater stream systems. Copyright © 2010 John Wiley & Sons, Ltd.     

Indikatorenbasierte Evaluierung von Fischhabitaten in alpinen Fließgewässern

The EU Water Framework Directive commits member states to achieve good ecological status in all waterbodies. Artificial or heavily modified waterbodies must reach at least its good ecological potential. In view of these requirements, simple and feasible methods are required in order to evaluate habitat suitability for relevant target species in larger river reaches. Well-developed models for determining the relationship between stream flows and habitat for target species mainly based on micro- and meso-scale already exist. However, the application of such models is complex and time-consuming and consequently limited to relatively short river segments. The objective of this study is to develop a simplified applicable assessment model to evaluate habitat conditions for selected target fish. This model uses hydro-morphological indicators for the habitat assessment and relies on correlative relations between habitat suitability and hydro-morphological features of river stretches (average Froude-number, relative flow width, mean bed slope, relative water depth and flow velocity). The indicators were determined as reach-related averages, derived from 2D model simulations (hydraulic and habitat-specific). Particular emphasis was laid on using a wide range of river stretches with different hydro-morphological characteristics (hydrology, bed substratum, bed structures, degree of braiding, sinuosity of the river course, mean bed width and bed slope). As a result, a set of model equations enables the evaluation of fish habitat conditions in river stretches as a function of flow and morphology. The habitat suitability assessment focuses on four preselected target species: brown trout, European grayling and for low slope rivers common nase and barbel.