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1.
Long‐term monitoring is critical for documenting population and community trends and for management, especially in large river‐floodplain ecosystems that provide important services. Levees have reduced active floodplains in most large rivers, but connectivity in some reaches could promote community resilience. Using multivariate tools and regression, we examined spatial and temporal structure in fish community samples from two decades (>1000 samples, >100 sites) in one of the largest relatively intact river‐floodplain ecosystems in North America – the Atchafalaya River (ARB), Louisiana. Assemblages exhibited significant structure temporally and spatially, with most substantial effects of year and hydrologic subdivisions; however, season and water level also influenced community structure. Temporal trends in communities were limited to few areas, while declines in species richness were more widespread; however, rarefied richness trends suggested that declines were slight. Recent and long‐term declines in abundance of economically important species (e.g., Black Crappie, Largemouth Bass, Bigmouth Buffalo) and increases in others (e.g., Smallmouth Buffalo, Blue Catfish, Freshwater Drum) drove differences among time periods. Our results suggest that the hydrologic subdivisions of the ARB may be an appropriate scale at which to manage fish populations, hydrology and water quality. Although we could not account for several important factors affecting fish communities in the ARB (e.g., hurricanes, major floods), and were limited by sampling variability, our findings highlight the utility of long‐term datasets from large river‐floodplain ecosystems for identifying important scales for management, determining species contributions to community change and forming hypotheses about anthropogenic and environmental drivers of variation in fish communities.  相似文献   

2.
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。  相似文献   

3.
Abstract –  This study aimed to evaluate otter predation on stocked trout. Large hatchery-reared trout (16–30 cm) were stocked into two Danish rivers with different fish populations. Otter diet before and after trout stocking was determined by analysing 685 spraints, collected regularly during the 35-day study period. Fish composition in the rivers before stocking was assessed by electrofishing. In River Trend, a typical trout river, the proportion of trout in the otter diet increased from 8% before stocking to 33% a few days after stocking. Moreover, trout lengths in the diet changed significantly towards the lengths of stocked trout, indicating that newly stocked trout were preferred to wild trout. In River Skals, dominated by cyprinids, there was no change in otter diet after stocking of hatchery trout, i.e., these were ignored by otter. Otter predation should be taken into account together with fish and bird predation, when stocking is used as a measure for conserving endangered salmonid populations.  相似文献   

4.
Abstract –  Many floodplain lake fish communities have been influenced by large-scale shifts in processes of water-level stability that degrade habitat quantity and quality. Efforts to restore rivers and their floodplains have recently taken a priority yet many restoration approaches are in their developmental stages and potentially controversial. We measured fish community changes in response to a water stabilisation technique in an Illinois River floodplain lake, achieved by levee renovations in 1997, using data collected prior to (1991–1993) and after (2000–2002) stabilisation. Our results indicate fish community composition (presence/absence) showed little variability and did not differ ( R  = 0.037; P  = 0.60) between the two time periods; whereas, fish community structure (abundance) differed ( R  > 0.50; P  ≤ 0.10). Increased abundances of desirable species like gizzard shad Dorosoma cepedianum (Lesueur), white crappie Pomoxis annularis (Rafinesque), black crappie Pomoxis nigromaculatus (Lesueur) and largemouth bass Micropterus salmoides (Lacepede), coupled with declines of less desirable species like common carp Cyprinus carpio (Linnaeus) contributed to community changes. These changes suggest positive responses to water stabilisation practices that may act as an intermediate step in restoring river–floodplain function in certain situations.  相似文献   

5.
Fish community composition is highly dynamic, but generally exhibits loose equilibrium within bounds of community structure in upland stream systems with minimal anthropogenic disturbance. Chronic anthropogenic disturbance can exceed ecological thresholds and shift fish community composition to an alternative state. Therefore, long‐term datasets are critical to understand spatiotemporal dynamics of fish community structure. We quantified temporal changes in fish communities in two Ouachita River systems during watershed alteration (i.e., development and reservoir construction) using a suite of multivariate and univariate analyses to assess changes in fish community structure and taxonomic and functional β‐diversity. We found fish community composition shifted in the Saline River basin possibly in response to human disturbance (e.g., development) and hydrologic variability. Furthermore, functional homogenisation occurred through time. In the Ouachita Headwaters basin, taxonomic homogenisation was evident and two fluvial specialists were not detected during the current period. Taxonomic and functional β‐diversity patterns were not consistent across basins demonstrating the complexity of biotic homogenisation. Our retrospective analyses showed human activities played a role in restructuring fish communities despite minimal invasion of exotic species. Ultimately, our study characterised fish community structure across snapshots of time and demonstrates the importance of increasing the frequency of sampling intervals and continuing long‐term collections with similar methods to enhance the understanding of community dynamics.  相似文献   

6.
为了解安宁河鱼类资源现状,于2013年3月至2014年12月对安宁河及其支流18个采样点进行了5次调查,共计采集鱼类3 113尾,隶属4目、10科、35属、52种,其中长江上游特有鱼类13种;鱼类区系包括中国平原、南方平原、南方山地、中亚山地、北方平原和晚第三纪早期6个区系复合体;其中,中亚山地区系复合体占优(40.4%)。安宁河不同河段Jaccard's相似性指数在0.12~0.47,鱼类群落相似性总体较低。根据IRI(100为优势种)指数计算结果,麦穗鱼(Pseudorasbora parva)、齐口裂腹鱼(Schizothorax prenanti)、红尾副鳅(Paracobitis variegatus)、西昌高原鳅(Triplophysa xichangensis)、斯氏高原鳅(Triplophysa stoliczkae)、东方高原鳅(Triplophysa orientalis)、鲇(Silurus asotus)和白缘鱼央(Liobagrus marginatus)8种鱼类为安宁河优势种。根据个体生物学测量,安宁河主要渔获对象规格较小,齐口裂腹鱼均重285.8 g/尾,红尾副鳅均重7.2 g/尾,鲫(Carassius auratus)均重78.3 g/尾,鲤(Cyprinus carpio)均重361.1 g/尾,鲇均重93.7 g/尾,表明可能存在过度捕捞现象。多样性分析显示,Margalef丰富度指数(R)在1.95~4.47,Shannon-Wiener多样性指数(H)在1.75~2.33,Pielou均匀度指数(E)在0.67~0.73。安宁河鱼类多样性相比同区域其它河流偏低,可能与安宁河鱼类群落受到各种干扰、生境异质性降低、鱼类群落已发生演替有关。对比历史资料,鱼类种类数从82种下降至52种,在不同区域的各分类阶元均有所减少,且有自上而下加重的趋势。水电开发、河道采砂以及资源不合理利用等是影响安宁河鱼类资源的主要因素。基于研究结果,建议尽快加强安宁河鱼类资源保护。  相似文献   

7.
Freshwater river mouths in large lakes are centres of biological activity, yet little is understood about the spatial and temporal dynamics of fish communities in these systems. In the Laurentian Great Lakes, we sampled littoral fishes over 3 years in six drowned (i.e., protected) river mouths to: (i) quantify spatial (among river mouths) and temporal (among years) variation, (ii) evaluate associations with environmental conditions and (iii) assess spatial patterns of community similarity. We sampled 6787 fish representing 43 species over the course of the study. Multivariate analyses indicated that variation in fish species composition was more strongly partitioned among river mouths than among years. Fish communities across the six river mouths were partitioned into three groups, a pattern we attribute to variability in anthropogenic disturbance and environmental conditions. Canonical correspondence analysis showed that fish species composition was associated with specific conductivity, vegetation cover, turbidity and pH, suggesting species–environment relationships are similar to those shown for Great Lakes coastal wetlands. Finally, we found a negative relationship between geographic distance and community similarity, suggesting that dispersal and/or environmental gradients play a role in shaping these river mouth fish assemblages. We conclude that Great Lakes drowned river mouths can harbour diverse and spatially variable fish assemblages that are driven by a combination of local and regional factors.  相似文献   

8.
Pander J, Geist J. Seasonal and spatial bank habitat use by fish in highly altered rivers – a comparison of four different restoration measures.
Ecology of Freshwater Fish 2010: 19: 127–138. © 2009 John Wiley & Sons A/S
Abstract –  River regulations have resulted in substantial modifications of the characteristics and the diversity of stream ecosystems. Fish habitat use in the context of species life histories and temporal habitat dynamics are crucial for the development of sustainable measures of habitat restoration in degraded rivers. The objective of this study was to compare the effects of introducing four different in-stream structures (bank ripp-rapp, benched bank ripp-rapp, successively grown riparian wood and artificial dead wood, nine replicates each) on the seasonal fish community distribution in a heavily modified stream ecosystem. Species richness and diversity, fish biomass and density showed strong variation (i) between habitat types, (ii) among replicates of the same habitat type, and (iii) in different seasons. The current low abundance of historical widespread rheophilic and migratory fish species in the study stream suggests that technical bank habitat restoration measures are only of limited use for the restoration of highly specialised target species in conservation such as Barbus barbus and Chondrostoma nasus . However, introduction of particular artificial stream structures (in particular of artificial dead-wood fascines) was found to concentrate biomass and density of none-specialised fish species like Squalius cephalus , Alburnus alburnus , Gobio gobio or Rutilus rutilus .  相似文献   

9.
Fish samples collected at the cooling water intake screens of West Thurrock power station located 35.5 km downstream of London Bridge on the Thames estuary during the decade 1980–1989 were analysed. Seasonal and long-term changes in the abundance of the 15 most numerous fish species and in several fish community parameters were analysed. The majority of species were highly seasonal in their distribution and abundance. Species diversity was lower in the summer (May–August) compared with spring/winter (October–February). Evidence of long-term changes in species diversity and community structure over the decade is presented. The changes were consistent with a period of relative stability (1980–1984) followed by a period of change (1985–1989) and may reflect a deterioration in water quality in the second quinquennium. It is argued that the monitoring of fish communities in estuaries should be based on a multi-metric approach as no single indicator alone can describe the complex community structure.  相似文献   

10.
Mickle PF, Schaefer JF, Adams SB, Kreiser BR. Habitat use of age 0 Alabama shad in the Pascagoula River drainage, USA. Ecology of Freshwater Fish 2010: 19: 107–115. © 2009 John Wiley & Sons A/S
Abstract – Alabama shad ( Alosa alabamae ) is an anadromous species that spawns in Gulf of Mexico drainages and is a NOAA Fisheries Species of Concern. Habitat degradation and barriers to migration are considered contributing factors to range contraction that has left just the Pascagoula River drainage population in Mississippi. We studied juvenile life history and autecology in three rivers within the drainage. We collected fish, habitat and physicochemical data in three habitat types (sandbar, open channel and bank) from June to October 2004–2006. Sandbar habitat was favoured by smaller individuals early in the year. Catch per unit effort (CPUE) decreased through the summer as larger fish began occupying bank and open channel habitat. The most parsimonious model of abundance included year and river variables, while patterns of presence and absence were best explained by river, habitat type and physiochemical variables. While all three rivers in the drainage contained Alabama shad, fish were less abundant and had lower condition values in the Chickasawhay River. Earlier work suggested the Alabama shad may gradually move downstream towards the Gulf of Mexico in their first year. However, we found no evidence of this and captured large fish high in the drainage late in the year.  相似文献   

11.
The European barbel Barbus barbus is threatened in areas of its range because of its sensitivity to anthropogenic disturbance in riverine habitats and, in the UK, is indigenous to a relatively small number of east‐flowing rivers, with nonindigenous populations present in other rivers following introductions for angling enhancement. Fish stock assessment surveys completed between 2002 and 2010 collated age and growth data from 20 rivers across their indigenous and nonindigenous UK range. Analyses revealed that individuals present in samples are of 21 years old, with growth rates highly variable between rivers. There was no relationship between growth rates and the maximum age of fish per river, and there was no difference in growth rates between their indigenous and nonindigenous ranges. A range of abiotic data were collated and analysed against the growth data; these analyses suggested higher mean growth rates were evident in rivers of higher biological water quality (expressed as British Monitoring Working Party Score) and higher mean air temperatures (used as a surrogate of water temperature). That growth of B. barbus was significantly and positively enhanced by increased biological water quality was in contrast to cyprinid fishes such as roach Rutilus rutilus and suggests that as river water quality continues to improve through reduced nutrient inputs, further ecological changes are likely in riverine fish communities.  相似文献   

12.
Abstract  Reliability of underwater snorkel counts of adult Atlantic salmon, Salmo salar L., was analysed in the tributaries of the River Teno, close to the spawning period. In small (width 5–20 m) rivers, the replicated total counts of salmon were reasonably precise (CV = 5.4–8.5%), while in the medium-sized river (width 20–40 m) the precision of the counting method was considerably lower (CV = 15.3%). Low precision in a medium sized river was also observed in an experiment using marked live fish where the observation efficiency varied between 36.4% and 70.0%. In a small river, the detection efficiency of artificial fish silhouettes (test salmon) was almost perfect in pools (98%), but decreased in rapids (84%). Separate counts of males, females, grilse and large salmon were usually more variable than total counts, indicating that divers were more capable of locating a fish than properly identifying its sex and sea-age. The behaviour of adult salmon was favourable to conduct snorkel counts, as fish normally stayed still, or after hesitating, moved upstream (>95%of the cases) when encountering a diver. The high observation efficiency (>90%) and precision, favourable behaviour of salmon and congruence between snorkel counts and catch statistics in small rivers suggest that reliable data on Atlantic salmon spawning stock can be collected by snorkeling provided that the environmental conditions are suitable and the divers are experienced.  相似文献   

13.
Abstract –  We examine patterns in fish species assemblages in the Toxaway and Horsepasture rivers, two high elevation streams in North Carolina, USA. This region is noted for extreme topographical relief, high cumulative annual rainfall and many rare and endemic plants and animals. The study area encompasses a portion of the Blue Ridge Escarpment and the associated Brevard Fault Zone. We hypothesise that major waterfalls and cascade complexes have acted to limit invasion and colonisation by fishes from downstream. This hypothesis is supported by longitudinal fish assemblage patterns in our study streams. Fish species richness in Toxaway River increased from 4 to 23 between Lake Toxaway and Lake Jocassee, a distance of 10 river km. We found similar discontinuities in neighbouring Horsepasture River and Bearwallow Creek. We found no instances of species replacement along this elevation gradient, and the trend in increased diversity downstream showed discontinuities coincident with sharp elevation breaks. With regard to theories posited to explain community formation in headwater stream fish communities (especially in those characterised by high topographical relief), we suggest coloniser 'access' may be more important than other factors including competitive interactions.  相似文献   

14.
  1. Fish assemblages in dryland rivers have life-history strategies that have evolved in response to environmental conditions and triggers, particularly water temperatures and flow regimes. The regulation of rivers through the construction of dams, weirs and other water diversion structures has altered natural flow regimes and the associated ecological processes of river systems worldwide.
  2. Over a 3-year period, using standardized fish sampling and daily otolith ageing, the recruitment of eight freshwater fish species was monitored in response to various abiotic drivers, including hydrology and water temperatures, throughout the Macquarie River, a large regulated river system of the Australian Murray-Darling Basin.
  3. A data-driven statistical classification system is provided that groups species into reproductive guilds, based on their recruitment response to hydrology and water temperature, specifically designed for use in environmental flow management.
  4. The eight species were grouped into three distinct reproductive guilds that showed similar recruitment responses to the abiotic drivers. Murray-Darling rainbowfish, Murray cod, and eel-tailed catfish were considered as a single guild, characterized by seasonal recruitment during a relatively narrow thermal window under low to moderate stable discharges. The second group included common carp, bony herring, and golden perch, which recruited primarily in association with larger flow events. Un-specked hardyhead and Australian smelt formed a more differentiated guild, recruiting over a broad range of temperatures and discharges. Limitations associated with using a reproductive guild approach to simplify water management are discussed.
  5. This study highlighted important relationships among hydrology, water temperatures, and successful recruitment that can, in turn, be used to inform development of adaptive flow management plans and effective use of environmental water for the conservation management of native fish communities. Important considerations in the design of studies that aim to examine relationships between recruitment and abiotic drivers are also discussed.
  相似文献   

15.
Abstract –  Recent work demonstrates that tributary inputs are important community reorganisation points for river biota; however, no studies have examined the long-term effects of tributary inputs on fish population dynamics. This study examines nearly 40 years of young-of-year (yoy) paddlefish recruitment data to investigate the hypothesis that tributaries influence mainstem fish population dynamics. We generated hydrological variables from daily mean flow data (1965–2007) from an impounded reach of the mainstem Missouri River and from the Niobrara River, a relatively unaltered tributary, using Indicators of Hydrologic Alteration software. Three multiple regression models using natural-log transformed catch per unit effort (log cpue) as the response variable were created using (1) Missouri River-only flow variables, (2) Niobrara River-only flow variables and (3) Missouri River and Niobrara River flow variables. Flow variables from the Niobrara River explain a greater proportion of yoy paddlefish log cpue variability demonstrating that tributaries can positively impact fish population dynamics in altered rivers.  相似文献   

16.
Abstract –  Spatial and temporal variation of species–environment relationships were evaluated for shallow-margin and deep-water fish assemblages in the Brazos River, a large floodplain river in Texas, USA. Total variation among the deep-water assemblages (11 species, 86% turnover across gill net samples) was greater than for shallow-margins (38 species, 64% turnover across seine samples). For both shallow-margin and deep-water assemblages, variation was greater among sites than between winter and summer seasons. Shallow-margin assemblage structure was related to depth, velocity and substrate, whereas for deep-water assemblages river discharge, temperature and velocity were important. Season itself accounted for little of the variation among either shallow (6.7%) or deep-water (2.3%) assemblages. Overall temporal patterns of shallow-margin samples appeared to show responses to juvenile recruitment, spates and migration of coastal fishes, whereas for deep-water samples, patterns related to use of reproductive habitats, juvenile recruitment and seasonal activity levels. Brazos River assemblages were less variable overall in comparison with studies along similar length of reach in headwater streams and wadeable rivers. The residual variation in species distribution (54% for shallow-margin and 67% for deepwater) that was not explained by instream variables and season suggests a greater influence of biotic interactions in rivers, particularly those across the spatially dynamic interface of main channel habitats and shallow river margins.  相似文献   

17.
为了解大渡河乐山段鱼类群落结构和多样性的分布特征,2015年11月至2017年4月,在大渡河河口乐山市沙湾区至市中区长约30km的河网段布置7个采样断面,采用定置刺网、地笼和电捕等方法,进行了4次鱼类资源调查。结果表明,调查期间共采集到鱼类57种,隶属于5目、13科、48属;其中,鲤形目(38种)占总数的66.67%;鲇形目(13种)占22.81%;鲈形目(4种)占7.02%;合鳃目(1种)和鳉形目(1种)均占1.75%。该区域鱼类群落以杂食性、底栖、适应缓流生境的种类为主。根据优势度指数(index of relative importance,IRI)分析,安谷电站坝上库区河段鱼类优势种有7种,坝下河段有8种,生态河道有8种。鱼类群落多样性指数以安谷电站坝下河段最高。生态类群分析表明,安谷电站坝上与坝下江段的鱼类群落结构差异显著,渔获物个体小型化趋势明显。目前的水电开发和过度捕捞是影响大渡河乐山段鱼类资源最主要的胁迫因素。  相似文献   

18.
Between 1979 and 1991, hatchery-reared 1+ and 2+ rainbow trout were released in May and June in the Boknafjord at the mouth of the River Imsa, and from April to June in the Oslofjord, southern Norway. The fish were recaptured in the fjords of release, in rivers emptying there and from rivers and sea further along the Norwegian coast. Of the total recaptures, 35.6% ascended rivers in the year of release. Some fish released at the River Imsa returned to the area of release after spending 1 to 3 years at sea. Among those that were recaptured in rivers, 11.9% were recaptured in other rivers than the Imsa. The growth rate of the fish varied inversely with size at release. The growth rate was higher in the Oslofjord than in the Boknafjord, and in both areas the growth rate decreased with time after release. Rainbow trout that had escaped from local fish farms entered the River Imsa between March and December. Adults ascending in spring remained a shorter time in the river (37 days) than those ascending in autumn (200 days). Fish entering in autumn decreased more in weight during their river stay than those ascending in spring, and females more than males. Spawning took place in April-May. The monthly mean river stay of juvenile entrants ranged from 2 weeks to 6 months. In total, 27.8% of the rainbow trout escaped from fish farms and captured in the Imsa strayed to other rivers for repeat spawning. There is no evidence for continuing survival of escaped Norwegian rainbow trout in the wild.  相似文献   

19.
Biotelemetry, ichthyoplankton and genetic data can provide detailed information about the migratory dynamics and reproductive cycle of freshwater fishes. However, few studies have combined these techniques in Neotropical systems. The objective of this study was to examine the migratory and reproductive dynamics of Prochilodus costatus in the São Francisco River watershed, south‐east Brazil, by comparing the ecological importance of two rivers to the species, an undammed segment of the São Francisco River and a dammed segment of one of its main tributaries, the Pará River. In total, 215 fish were radio‐tagged over three years (2014–16). Eggs and larvae were sampled at seven locations and analysed by PCR to identify Prochilodus spp. ichthyoplankton. Most radio‐tagged individuals (97%) used the undammed segment of the São Francisco River as spawning migration route, even those captured and released in the Pará River. Fish migrated to spawn from late September to late November with the arrival of the rains and returned to feeding sites from December to May after spawning. The highest densities of fish eggs and larvae were recorded in the upper reaches of the São Francisco River during months of peak river discharge. Returning fish showed high fidelity to sites occupied before spawning migration. Fish spent roughly 71% of the year at feeding sites, 25% at spawning sites and 4% moving between them. This study provides novel information about the migratory dynamics of Neotropical fishes and underscores the key role of undammed river segments for the conservation of Neotropical migratory fish species.  相似文献   

20.
基于2013年和2019年5-7月以及10-11月在小江回水区江段开展的鱼类资源调查及生境数据收集，采用多元分析方法量化分析了小江回水区江段非生物因子时空变动与鱼类群落结构时空变动的关系，揭示了三峡水库正常蓄水运行后小江回水区江段鱼类群落结构的时空变动特征及其驱动因素。研究结果显示：2013年和2019年共在小江回水区江段采集到鱼类74种，隶属于7目15科56属，其中优势种鱼类15种，长江上游特有鱼类7种、外来鱼类5种；小江常年回水区的鱼类群落结构在2019年时发生了明显的改变，而小江变动回水区江段的鱼类群落结构在2013年和2019年间无明显差异；小江常年回水区江段的鱼类群落结构在2013年时显示明显的季节性变动特征，然而在2019年时季节性变动特征变得不明显；小江变动回水区江段的鱼类群落结构在2013年和2019年时均显示明显的季节性变动特征；总磷含量、磷酸盐含量、水温和流速显著影响着小江回水区江段鱼类群落结构的时空变动格局，其中磷酸盐含量和水温是驱动小江回水区江段鱼类群落结构变动的最关键的两个因素。研究结果表明：尽量维持小江变动回水区的自然生境特征、采取措施控制小江常年回水区外来物种的数量以及严格控制外源营养物的输入，对于保护小江回水区江段土著鱼类的资源具有重要的意义。  相似文献   

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