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1.
Large‐scale patterns of fish diversity and assemblage structure in the longest tropical river in Asia 
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下载免费PDF全文 Although the Mekong River is one of the world's 35 biodiversity hot spots, the large‐scale patterns of fish diversity and assemblage structure remain poorly addressed. This study aimed to investigate the fish distribution patterns in the Lower Mekong River (LMR) and to identify their environmental determinants. Daily fish catch data (i.e. from December 2000 to November 2001) at 38 sites distributed along the LMR were related to 15 physicochemical and 19 climatic variables. As a result, four different clusters were defined according to the similarity in assemblage composition and 80 indicator species were identified. While fish species richness was highest in the Mekong delta and lowest in the upper part of the LMR, the diversity index was highest in the middle part of the LMR and lowest in the delta. We found that fish assemblages changed along the environmental gradients and that the main drivers affecting the fish assemblage structure were the seasonal variation of temperature, precipitation, dissolved oxygen, pH and total phosphorus. Specifically, upstream assemblages were characterised by cyprinids and Pangasius catfish, well suited to low temperature, high dissolved oxygen and high pH. Fish assemblages in the delta were dominated by perch‐like fish and clupeids, more tolerant to high temperatures, and high levels of nutrients (nitrates and total phosphorus) and salinity. Overall, the patterns were consistent between seasons. Our study contributes to establishing the first holistic fish community study in the LMR. 相似文献
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Abstract – Recognition of faunal changes requires long-term monitoring, which is lacking for all but a very few streams. Fish surveys are often focused on single, often imperiled, species. While such studies meet the goals of monitoring single species, assemblage-based data are required for detection of assemblage change and declines in common species, and yet these studies are relatively rare. Assemblage-based data may be important in identifying potential ecosystem problems before the loss of ecosystem function that results from catastrophic biodiversity decline. In 2005–2006, we sampled fishes in three streams in the Chattahoochee River drainage, Alabama in order to assess fish assemblage persistence and individual species declines. To achieve these comparisons we used historic data from two time periods, 1970s and 1995. Although comparisons to historical collections were used conservatively, we found dramatic assemblage shifts over time, even using conservative metrics. Examination of individual species persistence over time in these watersheds uncovered species losses at both the site and stream scale. Metrics of similarity, persistence, and Spearman's rank correlation indicated low similarity of fish assemblages and high species turnover over time. Specifically, cyprinid species have been lost and have been replaced with more cosmopolitan species. Comparison of three time periods allowed the estimation of when assemblages changed through time. Changes in land use, increases in the human population and less overall water availability may be agents of habitat degradation partially responsible for fish faunal changes. 相似文献
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The use of nature‐like fishways to increase ecosystem connectivity has increased in recent years, but their effectiveness has rarely been evaluated. A rock ramp was constructed in the Shiawassee River in 2009, and post‐construction effects (2011–2012) were evaluated on the summer fish assemblage by comparing fish assemblage composition to a nearby free‐flowing river and a nearby river with a dam. Patterns of fish species richness, mean catch‐per‐unit‐effort and proportional abundance in reaches upstream and downstream of the rock ramp, dam and comparable sites in the free‐flowing river were evaluated. Overall, species richness by site and proportional abundance in the rock‐ramp river were more similar to the free‐flowing river, while species richness by reach was more similar to the dammed river. These findings suggest that the rock ramp has improved connectivity for the summer fish assemblage, but has not fully restored conditions to the level observed in a free‐flowing river. 相似文献
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Salinity and geomorphology drive long‐term changes to local and regional fish assemblage attributes in the lower Pecos River,Texas 下载免费PDF全文
下载免费PDF全文 River systems throughout arid regions worldwide have been heavily impacted by human activities, resulting in long‐term ecological consequences. The lower Pecos River in the Trans‐Pecos region of Texas is no exception, having undergone anthropogenic changes that include decreased flow, elevated salinity, species loss and species invasion. We compared historical and contemporary fish assemblage attributes from the Pecos River at local (site‐specific) and regional (Trans‐Pecos region) scales across a 24‐year time period. Fish assemblage data were collected in October 1987 and 2011, by seining at 15 sites spanning 430 km of the river in Texas. Additionally, we examined contemporary environmental conditions to determine species–environment relationships. We found that fish assemblages were significantly different between time periods, likely due to increased salinisation in the upper half of the study region. Decreased species richness, species replacement and increases in euryhaline species were documented in the upstream sites. Freshwater springs lower the salinity and maintain flows in the downstream reach, allowing for maintenance of the native fish fauna. Careful management of regional aquifers, irrigation practices and petroleum waste water will be necessary for protecting biodiversity and environmental flows in the lower Pecos River. 相似文献
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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
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Fei Liu Jun Wang Fu‐Bin Zhang Huan‐Zhang Liu Jian‐Wei Wang 《Ecology of Freshwater Fish》2021,30(1):48-60
The Chishui River is the last free‐flowing tributary of the upper Yangtze River, China, which has an important role in fish conservation. This study aimed to explore the spatial organisation of fish assemblages in this river. Field sampling was conducted biannually between 2015 and 2017 at 41 sites from its headwater and downstream. One hundred and twenty‐two fish species were captured, including 34 endemic, 15 threatened and six exotic species. Fish assemblages varied significantly along the longitudinal gradient. Based on cluster and ordination analyses, 41 sampling sites could be divided into five site‐groups, corresponding to the headwater, upstream, midstream, downstream and the Xishui‐branch, respectively. The splitting of fish assemblages was consistent with the geographical divisions. However, fish species changed gradually along the longitudinal gradient rather than abruptly, which was consistent with the River Continuum Concept (RCC). In the headwaters and upstream, fish assemblages were mainly dominated by cold‐water and rheophilic species, while in the lower stretches, fish assemblages were dominated by warm‐water and limnophilic species. According to null models, fish assemblages were significantly nonrandomly structured at the basin scale, but randomly structured at the regional scale. This study is an important step in understanding the assembly rules of fish assemblages in this free‐flowing river and provides useful information for future fish conservation and ecological restoration. 相似文献
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- 1. The River Styles® framework is a geomorphic approach to the classification of river types, assessment of the physical condition of rivers, and planning of physical rehabilitation. However, the linkages between River Styles and aquatic biodiversity conservation are still only weakly developed.
- 2. In this study, 41 sites in the Bega River basin in New South Wales, Australia, were classified according to River Style and geomorphic condition, and surveyed for four biological assemblages: diatoms, aquatic and semi‐aquatic macrophytes, aquatic macroinvertebrates and fish.
- 3. Each assemblage differed significantly among River Styles. However, in the case of diatoms and fish, these differences could be accounted for by geographic clustering of sites in the same River Style, and a tendency for River Styles to occupy particular altitudinal zones and sizes of streams. This result was attributed to the overriding influences of water quality on diatoms and of altitude‐related variation in water temperature and distance from the ocean on fish. For macrophytes and macroinvertebrates, geomorphic river type appeared to exert a direct influence, probably via variation in physical habitat characteristics.
- 4. Geomorphic condition, judged as good, moderate or poor by reference to the inferred natural condition of each River Style, was also significantly associated with differences in biological assemblages other than fish. Twice as many taxa appeared to favour sites in good geomorphic condition as favoured sites in poor condition. Many of the taxa associated with sites in poor condition are alien taxa introduced to Australia since European settlement.
- 5. These findings imply that protection of reaches that are in good geomorphic condition is likely to be critical for the maintenance of indigenous biodiversity, and that rehabilitation of geomorphic condition can assist in the rehabilitation of native riverine biota.
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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
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Abstract – Fish assemblages from a historical (1968) pre-impoundment survey of the Bear Creek system (Tennessee River drainage) were compared with fish assemblages from recent collections to examine spatial recovery in stream fish assemblages. A positive relationship was present for species richness and distance from impoundment for recent collections but was not significant for historic collections from the same sites with distance superimposed from the impoundments. A positive relationship was also present for similarity and distance using Jaccard's Index and the Morisita Similarity Index. Recent fish assemblages were dissimilar to historical collections immediately below impoundments, but were increasingly similar at 10–20 km. The results suggest that recovery patterns for stream fish assemblages are present downstream for some types of impoundments and that remnants of the stream community persist downstream from existing impoundments. 相似文献
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Assessing long‐term fish responses and short‐term solutions to flow regulation in a dryland river basin 下载免费PDF全文
下载免费PDF全文 Water resource development and non‐native species have been cited as primary drivers associated with the decline of native fishes in dryland rivers. To explore this topic, long‐term trends in the fish community composition of the Bill Williams River basin were studied over a 30‐year period (Arizona, USA). We sampled 31 sites throughout the basin that were included in fish surveys by Arizona Game and Fish in 1994–97 and the Bureau of Land Management in 1979–80. We found that non‐native species have proliferated throughout the entire basin, with greater densities in the lower elevations. Native species have persisted throughout most of the major river segments, but have experienced significant declines in frequency of occurrence and abundance in areas also containing high abundances of non‐native species. Next, we assessed the short‐term response of the fish assemblage to an experimental flood event from the system's only dam (i.e. Alamo Dam). In response to the flood, we observed a short‐term reduction in the abundance of non‐native species in sites close to the dam, but the fish assemblage returned to its preflood composition within 8 days of the event, with the exception of small‐bodied fish, which sustained lower postflood densities. Our findings demonstrate the importance of natural flow regime on the balance of native and non‐native species at the basin scale within dryland rivers and highlight minimal effects on non‐native fishes in response to short duration flood releases below dams. 相似文献
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Patterns of fish species distributions replicated across three parallel rivers suggest biotic zonation in response to a longitudinal temperature gradient 下载免费PDF全文
下载免费PDF全文 Environmental gradients determine the distributions of individual species, which, in turn, shape patterns of species assemblage across those gradients. We used species distribution models to study the assemblage of fish species along the three mainstem rivers in the South Saskatchewan River Basin (SSRB) in Alberta, which flow in parallel across an 800‐km longitudinal span and down 1400 m from the Rocky Mountains to the Great Plains of North America. We estimated the similarity of species assemblages along each river to identify general patterns of species assemblage associated with temperature and five other physiochemical variables. Mean July water temperature, which ranged from <11°C at high elevation to >21°C at low elevation, was strongly associated with the presence–absence of most species in the SSRB. We found that high turnover occurred at two locations along the longitudinal gradient: where mean July water temperature was approximately 15°C and where mean July water temperature was approximately 19 or 20°C. There was also an increase in species richness at lower elevations where water temperatures were higher. Models incorporating forecasted changes in water temperature with climate change will likely provide accurate predictions of changes in the diversity and distribution of riverine fish communities across topographically heterogeneous landscapes. 相似文献
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While flow regime is widely recognised as an over‐arching feature structuring aquatic ecosystems, the influence of flood events on feeding habits in fish assemblages inhabiting variable environments remains largely unknown. In this study, we investigated how diets of a fish assemblage changed in response to fluctuations in hydrology in a highly variable, wet‐dry tropical Australian river. We compared dietary habits, trophic guilds and intra‐ and interspecific dietary overlap and diet breadth across different seasons. Wet‐season floods acted as major geomorphic and ecological perturbations that exerted substantial effects on the trophic dynamics of the terapontid assemblage, particularly through the removal of in‐stream plant production and detritus. Forced by major shifts in food source availability due to seasonal flooding, fishes responded to these perturbations by marked changes in diet, with significant guild switching following wet‐season floods. Rather than the predictable, gradual, changes in consumer–resource interactions associated with the gentler seasonal flood pulse evident in other tropical river systems, study results instead emphasised rapid and profound changes to species' diets and trophic interactions following abrupt flood pulses. These sudden shifts in food sources may also explain some of the lack of clarity in discrimination of specific carbon sources or species' trophic levels evident in isotopic food web studies from the region. Results indicate that the effects of flood pulses on assemblage trophic interactions may differ among ecosystem types and across the broad potential scale of hydrological disturbance mediated by flood events. 相似文献
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Eric W. Malone Joshuah S. Perkin William Keith Gibbs Matthew Padgett Matthew Kulp Stephen E. Moore 《Ecology of Freshwater Fish》2022,31(1):29-44
Understanding the ecological dimensions of drought is critical for predicting how humans and nature will be affected by the expected increased prevalence of drought in the future. We tested life-history-based predictions for fish assemblage responses to drought using retrospective analysis of long-term (1986–2003) fish surveys from two streams in the Appalachian Mountains of North America. We hypothesised that (1) fish assemblage composition would correlate with wet and dry hydrologic conditions as assemblages fluctuated within a loose equilibrium and (2) life-history traits of fishes would correlate with dry versus wet periods such that opportunistic life-history strategists would dominate during drought. Results showed fish assemblage changes in Little River and Cataloochee Creek correlated with drought severity measured one year prior to fish surveys. Fish assemblages at all three sampling sites in Little River and two sites in Cataloochee Creek fluctuated within a loose equilibrium, while the remaining two sites in Cataloochee Creek indicated directional change. Life-history traits for fishes in Cataloochee Creek correlated with one-year time lag fluctuations in drought caused by opportunistic species being dominant during drought and periodic/equilibrium species dominant during wet periods. Time series plots of fish abundances aggregated by life-history strategy revealed dominance of opportunistic species emerged at the onset of a multi-year drought spanning 1998–2004, particularly for the two sites undergoing directional change. Our work provides empirical evidence for theoretical linkages between life history and environmental fluctuations and can ultimately be used to predict stream fish community response to future drought regimes. 相似文献
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Fish assemblages in Atlantic Forest streams: the relative influence of local and catchment environments on taxonomic and functional species 下载免费PDF全文
下载免费PDF全文 Bianca de F. Terra Robert M. Hughes Francisco G. Araújo 《Ecology of Freshwater Fish》2016,25(4):527-544
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. 相似文献
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Nested patterns of spatial diversity revealed for fish assemblages in a west European river 总被引：1，自引：0，他引：1
A. A. Ibarra Y.-S. Park S. Brosse Y. Reyjol P. Lim S. Lek 《Ecology of Freshwater Fish》2005,14(3):233-242
Abstract – The longitudinal distribution of fish assemblages across a large west European river basin, the Garonne river (south-west France) were investigated using a self-organising map. This nonlinear statistical method was employed to classify sampling sites according to their species composition. We found three main nested patterns in an aggregated hierarchy: a replacement and succession of species along a gradient without defined boundaries, four main zones of fish assemblages and an upstream-downstream shift of fish communities. We suggest that fish assemblages are too complex to be identified with a single species as in the zonation model, and that the diversity patterns found might be part of the same ecological process influencing fish assemblages on different spatial scales. Thus, discrepancies in the analysis of longitudinal patterns of fish communities in streams may have been basically a matter of local conditions and of conceptual perception. 相似文献
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Long‐term fish assemblages respond to habitat and niche breadth in the West Fork White River,Indiana
Identification of patterns in community structure is a central theme in freshwater ecology. Our objectives were to identify temporal patterns in fish assemblages from 1980 to 2010 in the West Fork White River in east‐central Indiana using the Malthusian growth model and determine whether changes in the population growth rate parameter were related to Grinnellian niche breadth. We studied local‐scale fish assemblages in a Midwestern United States river at 16 sites for a period of 30 years. We used a hierarchical model to estimate population abundance parameters of the Malthusian growth model. Niche breadth was incorporated as a model parameter to explain variation in the population growth rate. Parameters of the model were fit using Bayesian inference. We identified notable changes in the fish assemblages; however, the patterns for temporal trends in individual species abundances were not conserved across sites. Decreasing trends were observed in longear sunfish, striped shiner, white sucker, central stoneroller, common carp and creek chub while bluegill and mimic shiner increased in abundance. Longear sunfish was the only species that exhibited the same trend in abundance for all sites. Niche breadth was inversely related to the population growth rate at sites adjacent to low‐head dam impoundments. We suggest that the presence of multiple impoundments has resulted in a fragmented series of fish assemblages. 相似文献
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Abstract – The dynamics of fish assemblages from seven floodplain lakes of Salado River (Argentina) was monthly analysed during two contrasting hydrological seasons. Partial canonical correspondence analysis indicated that assemblage structure was predictably linked to environmental characteristics that varied along temporal and spatial scales. Species distributed differentially along an environmental gradient of temperature, hydrometric level, conductivity, macrophyte cover and transparency in relation to their sensory capabilities (following piscivory‐transparency‐morphometry model) and life history strategies. During high water season, assemblages were associated with temperature and hydrometric level, factors which varied mainly across temporal scales and exhibit a regional range of action. During low waters, assemblage structure correlated with macrophyte cover and transparency, factors that varied fundamentally on spatial scales and have local impact. These results indicate that the determinism of fish assemblages does not vary substantially between hydrometric periods, although the environmental variables affecting fish assemblages and their scale of action are clearly different. 相似文献
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Montaña CG, Winemiller KO. Local‐scale habitat influences morphological diversity of species assemblages of cichlid fishes in a tropical floodplain river.Ecology of Freshwater Fish 2010: 19: 216–227. © 2010 John Wiley & Sons A/S Abstract – We examined the taxonomic and morphological diversity of cichlid fish assemblages in a floodplain river in Venezuela during the dry season at two spatial scales: macrohabitats (lagoons, main channels and creeks) and mesohabitats (leaf litter, sand banks, rocky shoals and woody debris). Nonmetric multidimensional scaling did not reveal differences for species assemblages among macro and mesohabitats. The first two axes from canonical correspondence analysis based on 19 species and six physical variables modelled >61% of the taxonomic variation in assemblages from rock shoals and woody debris, and 55% of variation in assemblages from sand banks and leaf litter. Principal components analysis based on 22 morphological variables yielded two dominant axes that explained >86% of variation in the cichlid assemblages. Morphological diversity was analysed to test the idea that assemblage structure is nonrandom, with structurally complex habitats supporting more species with more functional morphological diversity than simple habitats. Average and standard deviation (SD) of the morphological Euclidean distances of local assemblages among mesohabitats tended to decrease or be constant as the number of species increased. Regressions of the average nearest neighbour distance (NND) and SD of NND with species richness resulted in low and negative slopes of species assemblages among mesohabitats. These relationships suggest that when more species are added to a habitat patch, assemblage morphospace remains approximately constant, species average similarity increases and species dispersion in morphological space becomes more uniform. Results support that cichlids partition habitat at the local scale but not at the macrohabitat scale. 相似文献