Relative influences of environmental and spatial factors on stream fish assemblages in Brazilian Atlantic rainforest

Understanding the role of local and spatial factors in the structuring of aquatic communities is a goal in ecology. The hierarchical structure of stream systems provides opportunities to test the hypothesis that fish assemblages that are more isolated in headwaters are structured by local and/or regional variables. Fishes and abiotic data were collected in 18 stream reaches from two hydrographic basins in the Brazilian Atlantic rainforest. The variance of species composition was partitioned into fractions explained by environmental and spatial factors. The pure environmental fraction explained ≈17% of variance and was represented by regional, habitat availability/heterogeneity and perturbation gradient. The pure spatial fraction explained ≈15% of the individual fraction. Environmental data revealed a species sorting process, and the spatial effect might be a result of different dispersal routes that fish performed during the formation of the hydrographic basins, actual land use and water resources management. The importance of maintaining connectivity in these systems was emphasised because it cannot be guaranteed that the dispersion ability of species is still occurring under current land use change.     

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

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

Concurrent assessment of fish and habitat in warmwater streams in Wyoming

Abstract  Fisheries research and management in North America have focused largely on sport fishes, but native non-game fishes have attracted increased attention due to their declines. The Warmwater Stream Assessment (WSA) was developed to evaluate simultaneously both fish and habitat in Wyoming streams by a process that includes three major components: (1) stream-reach selection and accumulation of existing information, (2) fish and habitat sampling and (3) summarisation and evaluation of fish and habitat information. Fish are sampled by electric fishing or seining and habitat is measured at reach and channel-unit (i.e. pool, run, riffle, side channel, or backwater) scales. Fish and habitat data are subsequently summarised using a data-matrix approach. Hierarchical decision trees are used to assess critical habitat requirements for each fish species expected or found in the reach. Combined measurements of available habitat and the ecology of individual species contribute to the evaluation of the observed fish assemblage. The WSA incorporates knowledge of the fish assemblage and habitat features to enable inferences of factors likely influencing both the fish assemblage and their habitat. The WSA was developed for warmwater streams in Wyoming, but its philosophy, process and conceptual basis may be applied to environmental assessments in other geographical areas.     

The relative influence of spatial context and catchment‐ and site‐scale environmental factors on stream fish assemblages in a human‐modified landscape

Abstract – Environmental factors act in a hierarchical manner at multiple spatial scales to influence the organisation of ecological assemblages; however, the relative influence of the different scale‐related factor groups is poorly known. We evaluated the importance of catchment‐scale and site‐scale environmental variables, as well as the spatial context of the sampling sites, in shaping stream fish assemblages in an agriculture‐dominated landscape in Hungary. Beside the variables describing spatial context (principal coordinates of a truncated distance matrix among sites), altogether 60 environmental variables were used to predict variability using a variance‐partitioning procedure in redundancy analysis. Presence–absence‐ and relative abundance‐based data were examined at two assemblage levels (entire assemblage and native assemblage) at 54 stream sites. Incorporation of spatial variables increased largely the total explained variability in case of relative abundance, but not for presence–absence data. Of the environmentally explained variance, catchment‐scale variables (e.g., land cover types, patch density) were relatively more influential for the native assemblage‐level analyses, than for analyses at the entire assemblage level, where site‐scale variables (e.g., altitude, depth) proved to be more influential. In addition, pure catchment‐ and pure site‐scale variables have the primary role in determining fish assemblage patterns, whereas the influence of shared variance and that of site‐scale riparian variables proved to be less important. Our findings demonstrate the importance of incorporating the spatial context of the sampling sites in predicting fish assemblage patterns and the effects of channelisation (dikes) in shaping assemblage–environment relationships in this human‐influenced landscape.     

Evaluating effects of water withdrawals and impoundments on fish assemblages in southern New England streams,USA

Abstract Balancing aquatic conservation and water supply is becoming a major global issue for urban landscapes. The purpose of this study was to evaluate the ecological effects of stream‐flow alterations via water withdrawals and impoundments on fish assemblage structure. Electric fishing data were collected at 33 wadeable streams in Connecticut, located in the Southern New England region of USA. Fish sampling was conducted directly downstream of water withdrawals for municipal and agricultural water supply, and study sites differed in potential water withdrawal rates and the presence of impoundments. Regression analysis showed that water withdrawal rate was more important than other natural and anthropogenic factors (e.g. landcover and stream size) in explaining several fish assemblage metrics. Stream sites with high withdrawal rates were generally characterised by lower proportions of fluvial dependent fishes (fish which need flowing water to complete a portion of their life history) and benthic invertivores (fish which feed on bottom‐dwelling stream insects in riffle habitat), and had a greater percent composition of macrohabitat generalists, particularly members of the family Centrarchidae. Some assemblage metrics responded linearly with increasing magnitude of water withdrawals, but others were non‐linear. Results are consistent with ecological theory that alteration of the natural flow regime will impact stream biota.     

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.     

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

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Conserving fluxes of terrestrial invertebrates to trout in streams: A first field experiment on the effects of cattle grazing

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Conservation of newt guilds in an agricultural landscape of Belgium: the importance of aquatic and terrestrial habitats

• 1. Amphibians are declining worldwide in response to local and global pressures. Pond‐breeding species are particularly vulnerable to environmental change because they rely on two components of the landscape: aquatic and terrestrial habitats. Agricultural practices are changing rapidly at world and local scales. As a consequence, farm ponds and their surrounding terrestrial landscapes will probably be affected.
• 2. This study investigated the main habitat determinants for the occurrence of four species of newts (genus Triturus) inhabiting the Pays de Herve, a rural area in Belgium. Newt occurrence was determined for 258 ponds and the effect of habitat on distribution determinants was evaluated using generalized linear models.
• 3. Newts were found in 42% of the ponds. Contrary to expectations, the distribution of newts was not positively associated with a high density of ponds. However, a low occurrence of newts and the low water depth of many ponds suggest a low quality of habitats. Proximity to forest, deep water, and an absence of fish in ponds are factors that significantly favour newts, but terrestrial habitat requirements vary among species.
• 4. These results indicate the necessity of maintaining both forest and meadow patches in close proximity to ponds inhabited by newts, and of controlling fish introduction in those ponds. These findings stress the importance of conservation and management of terrestrial and aquatic habitats for maintaining amphibian diversity.

Copyright © 2007 John Wiley & Sons, Ltd.     

土地利用结构与景观格局对黎河水质的影响

黎河是引滦入津工程的唯一通道,本文以遵化市黎河为研究对象,选取了12个具有代表性的水质监测点,于2022年3月至6月进行水样采集,选用化学需氧量(COD)、氨氮(NH+ 4-N)、总磷(TP)、溶解氧(DO)和高锰酸盐指数(COD_Mn)5个水质指标进行检测。基于遥感数据和土地利用数据,利用GIS软件生成4种空间尺度的圆形缓冲区域,提取了不同空间尺度的景观格局指数,采用相关分析和冗余分析(RDA),探讨了土地利用结构与景观格局对水质的影响。结果表明：①黎河水质整体偏好,总体达到Ⅱ类标准,但仍存在超标水质,其中输水期水质明显好于非输水期。多数点位COD、TP值超过Ⅱ类水质标准限值,其余水质指标年均浓度均达到Ⅱ类以内水质标准。②不同尺度缓冲半径内占地类型均以林地、耕地、建设用地为主,建设用地、水域面积比例的增加可导致水质的恶化,林地、草地增加可对水质起到提升作用。③不同空间尺度缓冲区景观格局指数对水质具有较好的解释度,500m半径缓冲区景观格局对水质的解释能力最强,解释度达59.8%,其次为1000m尺度(56.0%)。因此,加强500m半径缓冲区尺度土地利用的优化对保护流域水质具有重要意义。研究结果可为合理优化流域土地资源提供基础参考,从而保护流域水质安全。     

Biodiversity and rarity distributions of native freshwater fish in an agricultural landscape: the importance of β diversity between and within water‐body types

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Effects of anthropogenic disturbances on α and β diversity of fish assemblages and their longitudinal patterns in subtropical streams,China

Identifying the spatial patterns of α and β diversity of biotics is an important yet little‐understood area of basic and applied ecological research. Although the upstream–downstream patterns of α diversity of stream fishes are numerously reported, β diversity has received less attention. In this study, we surveyed fishes along the upstream–downstream gradients in three headwater streams of the Qingyi River, China, which were affected by different extents of human activities. We aimed to assess how anthropogenic disturbances affect α and β diversity of stream fishes and their upstream–downstream patterns. We found that, compared with that in the Shuxi Stream disturbed less, endemic species decreased and cosmopolitan species increased in the Maxi and Puxi Stream disturbed heavily. The streams disturbed heavily showed lower α diversity and higher β diversity than that in the stream disturbed less. This among‐stream variations in fish diversity only occurred at the mid‐downstream, not upstream segments. α diversity increased downstream and β diversity decreased downstream from headwaters to mouth in the stream disturbed less, whereas this upstream–downstream pattern in fish diversity shifted in the streams disturbed heavily, in which both α and β diversity showed the quadratic distributions with the hump‐shape for α diversity and the U‐shape for β diversity respectively. Our results suggest that anthropogenic disturbances cause some cosmopolitan fishes replacing many endemic fishes in upland streams. This replacement processes result in α diversity decreasing and β diversity increasing, and shift the spatial patterns in fish diversity along the upstream–downstream gradient.     

Responses of anuran diversity to wetland characteristics and surrounding landscape in the Southern Andean Yungas,Argentina

1. Modification and loss of natural habitats caused by human activities are among the main drivers of biodiversity decline worldwide. To evaluate how land‐use changes affect species diversity at different spatial scales, amphibians represent an excellent group given that their complex life cycle requires both aquatic and terrestrial habitats.
2. In this study, the influence of wetland characteristics and surrounding landscape features on richness and functional diversity of anurans was investigated in 26 natural wetlands in a human‐modified landscape within the Southern Andean Yungas.
3. The analysis was performed at two spatial scales: wetland scale (the breeding pond structure) and the surrounding landscape scale. The classification of the landscape was limited to land uses modified by human activities within concentric circular buffers (radius = 0.1, 0.2, 0.5, and 1 km) centred on each breeding pond.
4. Generalized linear models were applied to investigate the relationship between environmental variables measured at different scales and anuran species richness and functional diversity, respectively.
5. Pond area best explained the observed variation in both diversity measures, which is consistent with other studies on anuran diversity in disturbed landscapes. In contrast to regression models including landscape scale variables only, integrated models (which included variables on both scales) highly improved model fit.
6. Conservation strategies for anuran species diversity in these altered Andean Yungas forests should include efforts to maintain or restore aquatic habitats (e.g. breeding ponds) placed within suitable landscapes.
7. Successful long‐term management will require an understanding of relationships between habitat characteristics at different spatial scales to identify variables that relate to species diversity in such heterogeneous habitats.

     

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.     

Effects of fisheries management on fish communities in the floodplain lakes of a Brazilian Amazonian Reserve

Abstract –  We compared fish abundance, diversity and species composition between lakes open (fished) and closed (no-take) to fishing activities in Mamirauá Sustainable Development Reserve in the Central Brazilian Amazon, in order to investigate potential influences of the common-based management. We sampled 1483 fishes from 70 species through gillnet fishing during the low-water season, in seven fished and seven no-take lakes. Contrary to expected, the mean values for abundance, size, diversity and species-richness of fish did not differ between fished and no-take lakes. There was no difference between fished and no-take lakes considering only the abundance of the 14 fish species more intensely targeted by fishermen. However, the abundance of an important commercial fish, the tambaqui ( Colossoma macropomum ) was higher in no-take lakes. Such data from a rapid assessment may be useful to monitor this and other fishery co-management schemes.     

The effects of ecoregions and local environmental characteristics on spatial patterns in boreal riverine fish assemblages

The conservation, management and monitoring of aquatic resources should benefit from understanding their spatial structuring. In this paper, we used the reference condition approach (RCA) to test if the variability in biotic communities, riverine fish assemblages in the present case, is better controlled with a spatial delineation based on ecoregions or by grouping rivers with local catchment characteristics. Electrofishing data from 493 riffles in 99 rivers in Finland were used in the analysis. We completed multivariate analyses (nonmetric multidimensional scaling, multiresponse permutation procedures) to identify differences in fish community composition among groups based on ecoregions or catchment characteristics. We concluded that both regional processes and local environmental characteristics structured fish populations, and bioassessment of freshwaters should be based on regional spatial delineations, supported by local scale characteristics. Spatial delineations like ecoregions should be used to assist the bioassessment to improve the efficiency to detect the human impacts.     

Relative influence of static and dynamic features on black‐footed albatross (Phoebastria nigripes) habitat use in central California Sanctuaries

Effective conservation of highly mobile species requires an understanding of the factors that influence their habitat use patterns, locally and within a large‐scale oceanographic context. We characterized the seasonal (chick‐rearing, post‐breeding) and inter‐annual (2004–2008) distribution and abundance of black‐footed albatross (Phoebastria nigripes; BFAL) along the central California continental shelf/slope using standardized vessel‐based surveys. We used a hypothesis‐based information‐theoretic approach to quantify the relative influence of environmental conditions on BFAL occurrence and abundance by assessing their association with: (i) local static bathymetric features, (ii) local and regional dynamic oceanographic processes, and (iii) seasonal and inter‐annual basin‐wide variability. While the presence/absence models yielded stronger results than the abundance models, both revealed that static and dynamic features influence BFAL habitat use. Specifically, occurrence was greatest near the shelf‐break, particularly in months with strong upwelling. High BFAL densities were associated with Rittenburg Bank, especially during the chick‐rearing season, periods of positive North Pacific Gyre Oscillation index and large northern monthly upwelling, evidenced by cool, salty waters in the study area. BFAL aggregation intensity was greatest onshore of the shelf‐break (200 m isobath). Behavioral observations reinforced the notion that transiting BFAL are widely dispersed near the shelf‐break and concentrate in large flocks of birds sitting on the water farther onshore. These results underscore the need to consider oceanographic processes at multiple spatial scales when interpreting changes in BFAL dispersion within marine sanctuaries, and highlight the feasibility of implementing bathymetrically defined protected areas targeting predictable BFAL aggregations within these larger management jurisdictions.