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.     

Habitat relationships with fish assemblages in minimally disturbed Great Plains regions

Abstract – Effects of local environmental influences on the structure of fish assemblages were evaluated from 159 sites in two regions of the Great Plains with limited anthropogenic disturbance. These regions offered an opportunity to evaluate the structure and variation of streams and fish assemblages within the Great Plains. We used canonical correspondence analyses to determine the influence of environmental conditions on species abundances, species occurrences and assemblage characteristics. Analysis of regions separately indicated that similar environmental factors structured streams and fish assemblages, despite differences in environmental conditions and species composition between regions. Variance in fish abundance and assemblage characteristics from both regions was best explained by metrics of stream size and associated metrics (width, depth, conductivity and instream cover). Our results provide a framework and reference for conditions and assemblage structure in North American prairie streams.     

River modification reduces climate resilience of brown trout (Salmo trutta) populations in Ireland

This study investigated interactions between eco‐hydromorphological state, riparian vegetation cover, water temperature and fish community composition in lowland rivers in Ireland. Physical habitat modification of study sites corresponded with degraded eco‐hydromorphological state (degree of ecological and physical modification) and reduced thermal buffering capacity (greater temperature fluctuation and increased frequency of extreme temperature events). This impact was reflected in the fish community, with a shift from a brown trout‐dominated (Salmo trutta L.) fish assemblage to predominance of the more thermally plastic minnow, Phoxinus phoxinus (L.), and stone loach, Barbatula barbatula (L.). Eco‐hydromorphological state may be a central factor affecting the ability of temperate rivers to resist temperature change in a warming climate and to maintain suitable conditions for salmonids and other cold‐water biota. Strategies aimed at climate change proofing of temperate rivers should focus on preserving or re‐establishing the eco‐hydromorphological processes that create habitat complexity and buffer stream temperature.     

Environmental assessment of boreal rivers using fish data – a contribution to the Water Framework Directive

Abstract A fish‐based assessment method was developed to estimate the ecological status of boreal rivers. Electric fishing data were collected from 902 rapids, together with information on the land use, channel modification and water chemistry. Discriminant function analysis was used to select fish variables that most correctly classified the undisturbed reference sites and human impacted sites into exact classes. The relationship between the level of human alteration and fish metrics was examined. Five metrics were selected for the index: the number of fish species, proportion of sensitive species, proportion of tolerant species, density of cyprinid individuals and the density of age‐0+ salmonids. The value for each metric (between 0 and 1) was calculated according to a point estimate for classical probability. The index is used to estimate the ecological classification of rivers according to the EU Water Framework Directive.     

Processes of collating a European fisheries database to meet the objectives of the European Union Water Framework Directive

Abstract  FIsh Database of European Streams, a common database for the FAME project, was merged using existing data on electric fishing and environmental data. FIsh Database of European Stream is a relational database with eight tables. Metrics based on classification of fish species into guilds were calculated, and provided in separate tables. FIsh Database of European Stream contained information about 150 freshwater fish species, from 12 countries, 17 ecoregions, 40 main river regions, 2651 rivers and 8228 sites. Examples of data coverage and use are given. Relationships between environmental variables were illustrated using principal component analysis, which resulted in three environmental components – latitude, size and altitude. Environmental component scores were correlated with fish metrics used in the European Fish Index. Results exemplify how fish guilds reflect gradients in environmental variation. Benefits and problems concerning standardisation and data availability at the global level are discussed.     

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.     

Influence of artificial headlands on fish assemblage structure in the surf zone of a sandy beach,Kashimanada Coast,Ibaraki Prefecture,central Japan

To determine the effects of artificial headlands (groins with an anchor-shaped head portion) on the surf-zone fish assemblage structure of a sandy beach with strong wave action, three study sites (headland site sheltered behind the head portion, pocket-beach site between two adjacent headlands and exposed reference site without headlands) were sampled on the Kashimanada Coast, central Japan, in summer and autumn in 2012 and 2013. Distinct differences in physical conditions were recognized between the headland site and the other two sites throughout the study period, the former being characterized by lower wave height and turbidity, finer sediment particles and richer detritus. The fish assemblage structures also differed among the sites, the headland site supporting greater species and individual numbers. Cluster analysis showed clear differences in species composition of fish assemblages between the headland site and the other two sites. In addition, small-sized fishes tended to be more abundant at the headland site compared with the other two sites, although no differences were apparent in fish assemblage structure between the pocket-beach and reference sites. These results suggested that the presence of headlands had marked effects on the surf-zone fish assemblage structure in the study area.     

Development of fish-based assessment method for the ecological status of rivers in the Baltic region

Abstract  A fish-based assessment method for determining the ecological status of rivers in the southern part of the Baltic region was developed, classifying fish assemblages of near natural sites, and testing the response of a wide range of fish metrics to human pressure. However, the potential for developing a statistically robust method was limited because of insufficient data and the impact of fishery exploitation. A combination of expert judgement, historical data and spatially based methods were needed to establish reference conditions and classification criteria for fish metrics. The final list of metrics (6–9 metrics per six different river types) comprises five ecological guilds (feeding, overall tolerance, habitat, migration and spawning strategy) and three sentinel (dominant) species ( Salmo trutta L., Cottus gobio L. and Alburnoides bipunctatus [Bloch]). The method tends to underscore the ecological status of specific river types because the selected metrics probably do not account for all possible variability in fish community response to degradation, as some community-specific characteristics were poorly or not represented. Exploitation pressure might have considerable effects on functionality of fish metrics. Results suggest that the method needs modification to account for these limitations.     

Restoration effort,habitat mosaics,and macroinvertebrates — does channel form determine community composition?

• 1. In certain lower mountainous regions of Germany multiple‐channel streams constitute the reference condition for stream restoration and conservation efforts. An increasing number of restoration projects re‐establish such stream sections, but their impact on macroinvertebrate communities remains vague and needs further elaboration.
• 2. Seven pairs of single‐ and multiple‐channel sections of mountain rivers were compared in terms of hydromorphology and macroinvertebrate communities. The stream sections were characterized by 16 hydromorphological metrics at various scales, e.g. shore length, channel feature or substrate diversity, flow variability and substrate coverage. Macroinvertebrate data were obtained from 140 substrate‐specific samples, which were combined to form representative communities for each section. Community data were subject to similarity and cluster analyses. Thirty‐five metrics were calculated with the taxa lists, including number of taxa, abundance, feeding type, habitat and current preferences.
• 3. Bray–Curtis similarity was very high (69–77%) between communities of single‐ and multiple‐channel sections. Biological metrics were correlated with hydromorphological parameters. Mean Spearman rank r was 0.59 (absolute values). The biological metrics percentage of the community preferring submerged vegetation, being grazers and scrapers or active filter feeders, percentage of epipotamal preference and the percentage of current preference (rheo‐ to limnophil and rheobiont) were significantly correlated with hydromorphological parameters.
• 4. Differences between stream sections can be attributed to single taxa occurring only in either the single‐ or multiple‐channel sections. These exclusive taxa were mainly found on organic substrates such as living parts of terrestrial plants, large wood, coarse particulate organic matter (CPOM) and mud. Reasons for high similarity of macroinvertebrate communities from single‐ or multiple‐channel sections are discussed, including the influence of large‐scale catchment pressures, length of restored sections and lack of potential re‐colonizers.

Copyright © 2008 John Wiley & Sons, Ltd.     

Effects of a rock‐ramp fishway on summer fish assemblage in a Lake Huron tributary

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.     

Fish‐based assessment of ecological status of Finnish lakes loaded by diffuse nutrient pollution from agriculture

Abstract The European Union Water Framework Directive stipulates that pressures on surface waters due to diffuse loading of nutrients have to be taken into account in determination of their ecological status. A Finnish data set of fish communities in 178 lakes was used to assess the effects of agriculture‐induced nutrient loads on the ecological status of lakes. The lakes were divided to reference (n = 100) and impacted sites (n = 78) based on water quality, land use and nutrient load data. Fish sampling was conducted by standardised gill net test fishing. A fish‐based classification tool of the four parameters (EQR4) was applied to assess the ecological status of lakes. The parameters included were: mean total biomass of fish per gill net night, number of fish individuals per gill net night, biomass proportion of cyprinid fishes and the presence of indicator species. The analysis resulted in a median EQR4 value of 0.78 (good status) for reference lakes and 0.56 (moderate status) for affected lakes. Thus, the classification tool gave an acceptable output for different nutrient‐loaded lakes.     

Fish assemblages in European Western Highlands and Western Plains: a type-specific approach to assess ecological quality of running waters

Abstract  After typological pre-classification of 398 calibration sites, fish-based metric models were used to predict the impact of human activities on river quality in European Western Highlands and Western Plains ecoregions. Calibration sites were grouped into six assemblage types and according to their geomorphology; test sites were assigned to their corresponding assemblage type. Five anthropogenic variables were used to describe the impact level of each site and stepwise discriminant analysis was performed to: (i) avoid redundancy between metrics; (ii) examine how selected metrics discriminated impact classes and (iii) predict ecological status for each site of the given fish type. Globally, this approach predicted the impact class correctly for 64% of sites. The difference between observed and predicted impact was more than one class for only 2.5% of the sites. When validating this approach with an independent data set, differences between observed and predicted impact values never exceeded 2 impact classes, but these differences varied in size among countries.     

A rapid biodiversity assessment methodology tested on intertidal rocky shores

• 1. Conservation managers require biodiversity assessment tools to estimate the impact of human activities on biodiversity and to prioritize resources for habitat protection or restoration. Large‐scale programs have been developed for freshwater ecosystems which grade sites by comparing measured versus expected species richness. These models have been applied successfully to habitats that suffer from systemic pressures, such as poor water quality. However, pressures in other habitats, such as rocky intertidal shores, are known to induce more subtle changes in community composition.
• 2. This paper tests a biodiversity assessment methodology that uses the ANOSIM R statistic to quantify the biological dissimilarity between a site being assessed and a series of reference sites selected on the basis of their similar environmental profile. Sites with high R values for assemblage composition have an anomalous assemblage for their environmental profile and are potentially disturbed.
• 3. This methodology successfully identified moderate to heavily perturbed sites in a pilot study on 65 rocky intertidal sites in south‐eastern Australia. In general, measures based on percentage cover (flora and sessile invertebrates) were more sensitive than abundance (fauna). Copyright © 2010 John Wiley & Sons, Ltd.

     

Revisiting ecological integrity 30 years later: non‐native species and the misdiagnosis of freshwater ecosystem health

Assessing the ecological integrity of freshwater ecosystems has become a priority to protect the threatened biodiversity they hold and secure future accessibility to the services they provide. Some of the most widespread applications of biological indicators are fish‐based indices. These have mostly mirrored the approach proposed by Karr 30 years ago (Index of Biotic Integrity; IBI), based on the comparison of observed and expected composition and structure of local fish assemblages in the absence of major perturbations, using the so‐called reference condition approach. Despite the notable success of the implementation of fish‐based indices, most of them overlook non‐native species as a source of ecosystem degradation, and evaluations are focused on the physico‐chemical condition of freshwater ecosystems and their effects on freshwater biodiversity. Almost 90% of 83 reviewed IBIs did not consider non‐native species when defining reference conditions. Most IBIs used non‐native species in conjunction with native ones to construct the metrics that conform to the index. The response of the IBI to the effect of non‐native species has hardly ever been tested. When developing and evaluating IBIs, attention was mostly directed to ensuring the correct response of the index to physico‐chemical parameters, which could otherwise be characterized more effectively using alternative methods. Current application of IBIs entails a misuse of biological indicators by overlooking some types of degradation that cannot be otherwise evaluated by traditional methods. This constrains the capacity to adequately respond to one of the most challenging and common threats to the conservation of freshwater fish diversity.     

Development and evaluation of a fish‐based index to assess biological integrity of Mediterranean streams

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Contrasting changes in freshwater fish assemblages and food webs follow modification of tropical waterways

Fresh waters are increasingly threatened by flow modification. Knowledge about the impacts of flow modification is incomplete, especially in the tropics where ecological studies are only starting to emerge in recent years. Using presence/absence data dated approximately four decades apart (~1966 to ~2010) from 10 tropical rivers, we assessed the changes in freshwater fish assemblage and food web after flow modification. The sites were surveyed with methods best suited to habitat conditions (e.g., tray/push netting for low‐order forest streams, visual surveys for canalised rivers and net casting for impounded rivers). With the presence/absence data, we derived and compared six measures of fish assemblage and food web structure: species richness, proportion of native species, overall functional diversity, native functional diversity, food web complexity and maximum trophic level. We found that changes in community assemblage and food web structure were not generalisable across modification regimes. In canalised sites, species richness and maximum trophic levels were lower in the second time period while the opposite was true for impounded sites. However, proportion of native species was consistently lower in the second time period across modification regimes. Changes in fish assemblages and food webs appear to be driven by species turnover. We recorded 79 cases of site‐specific extirpation and 117 cases of site‐specific establishment. Our data further suggest that turnover in assemblage is again contingent on flow‐modification regime. While the process was stochastic in canalised rivers, benthopelagic species were more likely to be extirpated from impounded rivers where species lost were replaced by predominantly alien fish taxa.     

Assessing electric fishing sampling effort to estimate stream fish assemblage attributes

The EU Water Framework Directive (WFD) obligates authorities to assess the ecological status of rivers. The sampling of the fish assemblage must be based on a reliable and cost‐effective monitoring programme, and it should be optimised to measure the ecological quality cost‐effectively. The efficiency of single‐pass versus three‐pass backpack electric fishing was measured to assess ecological status. The data included 295 electric fishing samplings from 137 rivers in Finland and a 5‐year data series from six small forest streams in mid‐eastern Finland. Compared with three‐pass electric fishing, single‐pass electric fishing in the same area increased the risk of missing rare fish species and species with low catchability. The concordance of the calculated fish metrics (e.g. proportion of tolerant and intolerant species) between one‐ and three‐pass measurements was, however, high, suggesting that single‐pass electric fishing was a suitable sampling procedure to evaluate ecological status. Increasing the area sampled by single‐pass removals stabilised the variances in the fish metrics and similarity indexes. It was concluded that in small streams electric fishing an area 24–27 times the stream width and in general a minimum of 300 m², but preferably more than 450 m², was adequate to estimate fish assemblage attributes reliably in boreal streams.     

Assessing long‐term fish responses and short‐term solutions to flow regulation in a dryland river basin

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.     

Development of a technique for Lake Habitat Survey (LHS) with applications for the European Union Water Framework Directive

• 1. In the absence of a standard procedure for characterizing the physical habitat of lakes in Europe, this paper describes the development of a multi‐purpose Lake Habitat Survey (LHS). The technique has been designed to meet the hydromorphological assessment needs of the Water Framework Directive (WFD), as well as to assist in monitoring the condition of designated sites in the UK and for wider application in environmental impact assessments and restoration programmes.
• 2. LHS involves detailed recording of shoreline features at a number of plots (Hab‐Plots), complemented by a meso‐scale survey of the entire lake, including shoreline characteristics and pressures, and modifications to the hydrological regime. A temperature and dissolved oxygen profile is also compiled at the deepest point of the lake (Index Site). Existing databases are exploited where possible, and remote sensing data (e.g. aerial photographs) are used to assist field‐based observations.
• 3. Initial field trials demonstrated that the consistency of the method, whether conducted by boat or on foot, was high. More than 250 surveys were carried out across the UK in 2004 through collaboration with the statutory environment and conservation agencies.
• 4. Two levels of complexity were tested — a full version requiring 10 Hab‐Plots and an abridged version, LHS_core, involving four plots and omitting the Index Site. While 8–10 plots were required to capture the full diversity of features at complex sites, LHS_core data were sufficient to generate metrics for classification purposes.
• 5. A Lake Habitat Modification Score (LHMS) may be calculated from LHS data. This synthesizes a wide array of hydromorphological and human pressures and has direct applications for assessment of ecological status under the WFD. Preliminary analysis illustrates a spectrum of hydromorphological alteration of 82 lakes in the UK.
• 6. Further considerations are discussed, including the prospect that the LHS protocol might form the basis of a European standard developed through CEN (Comité Européen de Normalisation).

Copyright © 2006 John Wiley & Sons, Ltd.