Effects of small hydropower plants on fish assemblages in medium‐sized streams in central and northern Portugal

• 1. Over the last decade the development of small hydropower projects has been one of the most active areas of the energy sector. One of the main environmental challenges faced by such projects is related to fish passage.
• 2. The impact of 18 small hydropower plants (SHPs) with distinct levels of fish‐pass effectiveness was investigated in the summers of 1998 and 1999 by comparing fish assemblage composition and structure at 36 sites, above and below SHPs.
• 3. With regard to effectiveness, it was estimated that eight (44.4%) of the surveyed passage facilities were suitable for target species, whereas the remaining 10 (55.6%) were considered unsuitable. In neither case did the composition of fish assemblages upstream and downstream from SHPs differ significantly, while assemblage similarity was relatively high.
• 4. Multivariate techniques identified cover, depth and coarse substrate as the main parameters structuring fish assemblages. It is suggested that these variables have created a rich, patchy, heterogeneous habitat, thereby providing satisfactory resources and favourable conditions required by fish and contributing to the maintenance of assemblages.
• 5. Although populations of some species that occurred both upstream and downstream from SHPs have developed differences in their size structures, SHP‐induced fragmentation of fish populations may not necessarily result in genetic divergence among semi‐isolated populations.

Copyright © 2006 John Wiley & Sons, Ltd.     

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.     

Fish–habitat relationships and fish conservation in small coastal streams in southern Spain

• 1. Studies dealing with the fish fauna of coastal streams are scarce in the scientific literature, particularly those from Mediterranean climates. Owing to their small size, these systems suffer extreme seasonal fluctuations, following the typical Mediterranean flood–drought cycle and leading to a high risk of extinction to freshwater fish.
• 2. This work analyses fish distribution in 14 stream stretches belonging to eight basins in the northern sector of the Strait of Gibraltar (southern Spain). Fish–habitat relationships were studied through multivariate ordination techniques at two scales: basin and stretch.
• 3. A principal components analysis clearly discriminated larger and more sinuous basins from smaller and steeper ones. This ordination was related to the non‐migratory freshwater fish species richness and to the total number of fish species present in the middle reaches of each basin.
• 4. The main sources of variation in community composition and habitat characteristics in the different stretches were related to a clear upstream–downstream gradient, along which total species richness increased.
• 5. These small coastal basins are inhabited by two highly endangered species, Andalusian toothcarp (Aphanius baeticus) and Iberian chub (Squalius pyrenaicus), and have similar or higher overall freshwater species richness than larger adjacent basins. The near absences of flow regulation and introduced species make these streams one of the few types of Iberian aquatic system where unaltered fish–habitat relationships can be studied.

Copyright © 2005 John Wiley & Sons, Ltd.     

Distribution modelling to guide stream fish conservation: an example using the mountain sucker in the Black Hills National Forest,USA

• 1. Conservation biologists need tools that can utilize existing data to identify areas with the appropriate habitat for species of conservation concern. Regression models that predict suitable habitat from geospatial data are such a tool. Multiple logistic regression models developed from existing geospatial data were used to identify large‐scale stream characteristics associated with the occurrence of mountain suckers (Catostomus platyrhynchus), a species of conservation concern, in the Black Hills National Forest, South Dakota and Wyoming, USA.
• 2. Stream permanence, stream slope, stream order, and elevation interacted in complex ways to influence the occurrence of mountain suckers. Mountain suckers were more likely to be present in perennial streams, and in larger, higher gradient streams at higher elevations but in smaller, lower gradient streams at lower elevations.
• 3. Applying the logistic regression model to all streams provided a way to identify streams in the Black Hills National Forest most likely to have mountain suckers present. These types of models and predictions can be used to prioritize areas that should be surveyed to locate additional populations, identify stream segments within catchments for population monitoring, aid managers in assessing whether proposed forest management will potentially have impacts on fish populations, and identify streams most suitable for stream rehabilitation and conservation or translocation efforts.
• 4. When the effect of large brown trout (Salmo trutta) was added to the best model of abiotic factors, it had a negative effect on the occurrence of mountain suckers. Negative effects of brown trout on the mountain sucker suggest that management of recreational trout fisheries needs to be balanced with mountain sucker conservation in the Black Hills. However, more spatially explicit information on brown trout abundance would allow managers to understand where the two species interact and where recreational fisheries need to be balanced with fish conservation.

Copyright © 2008 John Wiley & Sons, Ltd.     

Morphological divergence of the threatened Rocky Mountain sculpin (Cottus sp.) is driven by biogeography and flow regime: Implications for mitigating altered flow regime to freshwater fishes

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How deforestation drives stream habitat changes and the functional structure of fish assemblages in different tropical regions

1. Deforestation can modify stream habitat and the functional structure of fish assemblages. The aims of this study were (a) to identify whether deforestation has a similar effect on local habitats from two biogeographically distinct river basins in a tropical region; (b) to identify how fish trait–habitat relationships were influenced by deforestation; and (c) to compare functional redundancy patterns in these basins.
2. Environmental and biological variables were obtained for 160 stream reaches, 85 located in the Alto Paraná River basin and 75 in the Machado River basin. Traits were associated with body size, habitat preference, food items and foraging period. Linear models were constructed to verify the environmental convergence of habitats across streams from the Alto Paraná and the Machado basins. An RLQ and a fourth‐corner analysis were conducted to investigate how deforestation affected habitat variables and trait–habitat relationships. The nearest relative index (NRI) was used as a functional redundancy measure.
3. Deforestation led to a similar habitat gradient from streams with a higher proportion of coarse roots in more forested catchments to streams with streamside grasses, bare soil and unconsolidated substrate in more deforested catchments; however, a general pattern of fish trait–habitat relationships was not identified across basins. Functional redundancy was associated with a long history of habitat loss in the Alto Paraná streams, whereas functional complementarity was related to more recent and less intense habitat loss in Machado streams.
4. We believe that differences in regional species pools and historical processes between the basins influenced the fish functional responses to deforestation. Nevertheless, the results highlighted the importance of stream habitat heterogeneity and the presence of preserved forest fragments in a region to prevent the loss of unique traits. Decision‐makers should therefore maintain large forest fragments and restore riparian forests to preserve stream habitat and the functional structure of fish assemblages.

     

If you build it,they will go: A case study of stream fish diversity loss in an urbanizing riverscape

1. Stream fish diversity is threatened by anthropogenic environmental alterations to landscapes, and successful conservation requires knowledge of the processes that degrade diversity. A primary step in identifying diversity losses is the comparison between historical and contemporary states of landscapes and fish assemblages, but uncertainty remains regarding the appropriate spatial scales of investigation.
2. Historical data collected in 1976 were paired with two years of contemporary replication (2015, 2016) to assess fish diversity change at 10 sites in Blackburn Fork, TN, USA. Analyses focused on a nested hierarchy of spatial scales, including sampling sites (fine scale), nested within stream orders (intermediate scale), nested within the entire catchment (broad scale). Diversity change between 1976 and 2015–16 was assessed using traditional diversity metrics (site scale) and rarefaction (stream‐order scale), whereas spatial variation in contemporary diversity (2015–16) was assessed with nonmetric multidimensional scaling (catchment scale).
3. At the site scale, locations on the east side of Blackburn Fork and in close proximity to developed land experienced diversity loss. At the stream‐order scale, the effective number of species declined in first‐order streams where land development was concentrated, but no consistent species losses occurred in other stream orders. At the catchment scale, assemblages responded significantly to stream size but not land use, perhaps because diversity was already homogenized by 2015–16. Mapping 40 years of land‐use change across the catchment underscored a pattern of spatial alignment between developed lands and stream fish diversity loss.
4. This study highlights the benefits of considering multiple spatial scales when assessing historical change in stream fish assemblages, and highlights stronger inference derived from historical comparisons relative to contemporary space‐for‐time substitutions. This framework combines recent analytical advances in rarefaction with a riverscape perspective, and can be applied to conserve streams, and their biota, in riverscapes around the world.

     

Dams in the Amazon: The importance of maintaining free-flowing tributaries for fish reproduction

1. Free-flowing tributaries are important for the maintenance of fish diversity in dammed systems. In relation to the reproduction of fish species, the role of a free-flowing tributary was evaluated and compared with that of a dammed tributary downstream of large dams in the Madeira River, one of the main tributaries of the Amazon River.
2. Two hypotheses were tested: (i) the densities of the ichthyoplankton differ between the dammed and the free-flowing tributaries; and (ii) the free-flowing tributary contributes a greater diversity of fish larvae species to the assemblage structure of the main stem than the dammed tributary.
3. Fish eggs and larvae were sampled at five sites: one in each tributary (Jamari – dammed – and Machado – free-flowing) and three in the main stem (Madeira River), upstream and downstream from the mouth of each tributary.
4. Fitted Bayesian models showed that the densities both of eggs and larvae were more than twice as high in the free-flowing tributary than in the dammed tributary. The results also indicated that the free-flowing tributary makes a major contribution to the fish assemblage structure of the Madeira River, whereas the dammed tributary does not have a significant influence on the main stem assemblage structure.
5. The results demonstrate the importance of conservation and maintenance not only of the Machado River but also of other free-flowing tributaries in dammed basins, especially those basins with high biodiversity, such as the Amazon. Moreover, this study helps inform the decision-making process regarding the location of new dams, which is critical in fish diversity conservation.

     

Fish invading deserts: non‐native species in arid Moroccan rivers

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Country‐wide analysis of large wood as a driver of fish abundance in Swedish streams: Which species benefit and where?

1. Rivers are heavily affected by human impacts that threaten many fish species. Among restoration measures, the addition of large wood (LW) in streams has been shown to increase fish abundance, yet which species benefit from LW, to what extent relative to other drivers, and which factors influence LW quantity is not clear, and these uncertainties limit our ability to use LW as an effective restoration measure.
2. Here, a time series (from 1993 to 2016) of electrofishing data, including 3641 streams across Sweden, was used to investigate the beneficial effects of LW on the abundance of juvenile brown trout, Salmo trutta, juvenile Atlantic salmon, Salmo salar, and juvenile and adult sculpins, Cottus gobio and Cottus poecilopus, while accounting for other abiotic and biotic factors, and the drivers of LW abundance at a country‐wide scale.
3. Large wood benefitted brown trout, and the effects were greater with decreasing shaded stream surface. LW effects were comparable in magnitude to the positive effects of average annual air temperature and the negative effects of stream depth and predator abundance – factors where the influence was second only to the negative effects of stream width. LW did not benefit salmon abundance, which was correlated positively with stream width and negatively with altitude, nor did it benefit sculpin abundances, which mainly decreased with annual average air temperature and altitude.
4. The quantity of LW strongly diminished with stream width, and, to a lesser extent, with stream depth, altitude, annual average air temperature, and forest age, whereas it increased with stream velocity, slope, and forest cover.
5. The results suggest that LW can be used as an effective restoration tool for brown trout in shallow and narrow streams, especially in areas with little shade. Here, the addition of LW may help to alleviate the impacts of forest clearance and climate change.

     

Rapid response of fish and aquatic habitat to removal of a tidal barrier

1. River barrier removal is used increasingly as a conservation tool to restore lotic habitat and river connectivity, but evidence of its efficacy is incomplete. This study used a before–after methodology to determine the effects of removing a tidal-limit barrier on the fishes, macroinvertebrates, and habitats of an English coastal stream.
2. Following barrier removal, habitat diversity increased immediately upstream and remained similar downstream. Mobilized silt altered the substrate composition immediately downstream, but this was temporary as silt was flushed out the following winter. Changes to macroinvertebrate communities occurred upstream and downstream of the former barrier but these were transient.
3. A dramatic and sustained increase in fish density occurred immediately upstream of the barrier after its removal, but effects downstream were minor. The fish community upstream changed, largely due to rapid recruitment and dispersal of endangered European eel (Anguilla anguilla). Eel density in the formerly impounded zone increased from 0.5 per 100 m² before barrier removal to 32.5 per 100 m² 5 months after removal. By 17 months after barrier removal there was no difference in eel density across the six sections sampled.
4. Although resident stream fishes such as bullhead (Cottus gobio species complex, protected under the European Habitats Directive) were abundant in middle and upper-stream sections, brown trout (Salmo trutta, a listed species for biodiversity conservation in England and Wales) density remained low during the study and recruitment was poor. This suggests that although colonization access for anadromous trout was available, habitat upstream may have been unsuitable for reproduction, indicating that wider catchment management is required to complement the restoration of connectivity.
5. These findings suggest that tidal barrier removal is an effective method of restoring lotic habitats and connectivity, and can be beneficial for resident and migratory fishes including those of conservation importance (e.g. European eel) in coastal streams.

     

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。     

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.     

Mixed stream channel morphologies: implications for fish community diversity

• 1. Stream classification systems are widely used in stream management and restoration. Whereas the principal morphological types of these classification systems are increasingly recognized for their ecological connections, the roles of intermediate and mixed morphologies are still poorly understood, yet may be biologically significant.
• 2. Twenty‐five stream reaches in north‐western Vermont were classified by channel morphology to determine whether fish community diversity differed among pool‐riffle, mixed (i.e. pool‐riffle/cascade, pool‐riffle/other) and forced pool‐riffle stream morphological groups. Stream reach surveys included cross‐sectional surveys, longitudinal profiles, bed substrate characterization, and fish surveys.
• 3. Three fish community diversity measures were calculated: (1) species richness (S); (2) Shannon–Weaver Index (H′); and (3) Simpson's Index (1/D). Multivariate analysis of covariance (MANCOVA) followed by analysis of variance (ANOVA) were used to explore potential differences in fish diversity among stream morphological groups. Fish diversity was significantly different for all three community diversity measures (P?0.05), with pool‐riffle/cascade morphology consistently exhibiting the greatest fish diversity and forced pool‐riffle the lowest.
• 4. These results suggest that fish community diversity is significantly associated with distinct channel morphologies. Generally, pool‐riffle/cascade and pool‐riffle/other stream morphological groups supported habitats that fostered greater species diversity than more homogeneous and uniform pool‐riffle reaches. The observed patterns of diversity are likely to be the result of habitat patches created by variations in flow and other physical characteristics in reaches of mixed morphologies.
• 5. These results support fish sampling schemes that incorporate morphological heterogeneity, such as proportional‐distance designation. Sampling strategies that focus on homogeneous reaches may underestimate diversity, and misrepresent stream condition when fish community data are used in indices of biological integrity (IBIs). Reaches of mixed stream morphologies should be recognized as areas of biological importance in stream and catchment management and in conservation efforts.

Copyright © 2008 John Wiley & Sons, Ltd.     

Historical changes in fish communities in urban streams of the south-eastern United States and the relative importance of water-quality stressors

A total of 71 stream sites representing a gradient of urban land use were sampled across the Piedmont of the south-eastern United States in 2014. Fish data collected (observed) at each site were compared to an expected community based on georeferenced historical (~1950 - ~1990) species occurrence records for stream segments (1:100,000 scale) containing the sampled stream sites. Loss of expected fish species (per cent of fish species expected to occur but not observed) and homogenization (difference in Jaccard's similarity of the fish community among sites observed and expected) were determined. On average, there was a 13.2% increase in the similarity of fish communities across sites, demonstrating evidence of community homogenization. Occurrence of Redbreast Sunfish (Lepomis auritus), Green Sunfish (L. cyanellus) and Bluegill (L. macrochirus) increased more than 50% over time (between observed and expected). Species loss increased significantly with urbanization, whereas homogenization was not related to urbanization. Random forest analysis indicated that herbicides, insecticides and centrarchid species richness were significant predictors of species loss. Of these, generalized additive model regression indicated that herbicides represented the most parsimonious model based on a single predictor. Stream base flow, elevation and total nitrogen were significant predictors of homogenization. Generalized additive model regression indicated that decreased stream base flow was the single most important factor associated with increased homogenization. Chemical contaminants and associated ecosystem alteration and changes in streamflow may represent important regional influences on changes in fish communities in urban streams in the south-eastern United States.     

Conservation of fish communities: Extending the ‘research life cycle’ by achieving practical effects

1. This article highlights the practical impact of our 2018 Aquatic Conservation: Marine and Freshwater Ecosystems publication, ‘Importance of peripheral basins: Implications for the conservation of fish assemblages’, which described fish communities in a Polish river.
2. Data on the fish assemblages of the Dniester River (Black Sea basin) are scarce; however, evidence indicates that the assemblages have declined. In our 2018 study, we hypothesized that the peripheral basin (the small basin on the edge) of the larger Upper Dniester River basin (the Strwi?? River) could maintain good ecological status and contained unique fish assemblages.
3. To examine the influence of historical factors and assess the role of peripheral basins on fish conservation, data from the Strwi?? basin were compared with the adjacent but unconnected Wiar basin (the Vistula basin; Baltic Sea basin). The Strwi?? River fish assemblages featured higher species richness and a greater number of native Ponto–Caspian species that function near the edge of their ranges.
4. This article focuses on four impacts of the 2018 publication: increasing awareness by various groups and organizations of the unique character of the surveyed river basin; highlighting important issues in assessing the ecological status of European rivers; driving the red‐listing of species and the development of stream fish conservation strategies; and identifying possible future impacts.
5. Our 2018 publication demonstrated the value of studying peripheral basins, which may affect conservation strategy development and encourage study of the importance of other peripheral basins and their role in aquatic resources conservation. Our article influenced the interpretation of fish‐based biotic indices and the conduct of monitoring work and its evaluation. It also strongly emphasized the native origin of the racer goby (Babka gymnotrachelus) in the Strwi?? River, which was important for subsequent works seeking to change the legal status of the species in Poland.

     

Associations between stream hydrogeomorphology and co‐dependent mussel–fish assemblages: evidence from an Ohio,USA river system

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Habitat mapping and conservation analysis to identify critical streams for Arizona's native fish

• 1. Arizona's native fish species are among the most imperilled fauna in North America. Knowing the current distribution of native fish and their habitat is critical to their management and conservation, but the last detailed mapping effort was more than 30 years ago and pre‐dated computer mapping techniques.
• 2. Current distribution of 34 native fish species was modelled by identifying perennial stream segments for which species presence had been documented. A composite of these single‐species maps displays a pattern of species richness that can inform conservation, especially when overlaid with maps of management status or invasive species.
• 3. The map overlays suggest that conservation priorities should include Eagle Creek, the Verde River and its tributaries, Aravaipa Canyon, the Virgin River and Black Draw, which together hold 63% of native fish species. Of the 32 streams that support five or more native species, 28 have at least one non‐native fish species, indicating that a more aggressive programme of removing non‐natives may be critical to maintaining those native populations.
• 4. The U.S. Forest Service and Native American tribes administer the majority of occupied stream habitat (30% and 27%, respectively). While private lands hold the third‐highest amount of occupied habitat (19%), they control streams occupied by the greatest total number of native species (30). Conservationists should work more with private land owners, while also coordinating efforts with the U.S. Forest Service and North American tribes.
• 5. These data are publicly available (on the Internet, URL: www.azconservation.org ) to encourage refinement and use.

Copyright © 2006 John Wiley & Sons, Ltd.