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Challenges in developing fish-based ecological assessment methods for large floodplain rivers
Fisheries Management and Ecology, 2007
Large European floodplain rivers have a great diversity in habitats and fish fauna, but tend to be heavily modified. The complexity of these river systems and their multiple human impacts pose considerable challenges for assessment of their ecological status. This paper discusses: (1) the application of historical information on fish fauna and habitat availability to describe reference conditions; (2) responses of fish assemblages to human disturbance by comparing various rivers and river segments with different impacts and/or time series within rivers; (3) the role of floodplain water bodies in ecological assessment; and (4) monitoring of large rivers using different gears and sampling designs for main channels and floodplain habitats. The challenge for the future is to
The biological assessment of lotic resources in much of the U.S. and Canada initially focused on wadeable rivers and streams. However, increased emphasis is being placed on larger, non–wadeable rivers. Many of these efforts include the development of multimetric indices represented by the Index of Biotic Integrity (IBI) following the original developmental work in the U.S. They include the pioneering work in the Wabash River of the Midwestern U.S., the inland rivers of Ohio and Wisconsin, the Ohio River mainstem, large western rivers and Quebec rivers, all of which focused on the fish assemblage. Monitoring fish assemblages in large rivers includes logistical and technical considerations that affect obtaining reliable estimates of relative abundance for all species that are amenable to efficient capture. A single gear approach is preferred for practical reasons and electrofishing is the sampling method of choice. Sampling effort is expressed in terms of distance sampled at a site and includes formulas based on fixed distances or multiples of river channel width. Relative abundance data are analyzed via multimetric indices (e.g., Index of Biotic Integrity), which are contingent on the development of a reference condition that supports a derivation and calibration process. Defining reference for large rivers represents a different challenge than with smaller, wadeable streams. For the latter, sufficient and suitable reference analogs usually exist, thus reference condition can be empirically derived. However, such analogs are either rare or do not adequately reflect the restorable potential for large rivers. Thus in developing the expectations that are necessary for metric calibration and IBI development, adequate historical knowledge of the assemblage is critical. Once developed, the metrics and indices provide meaningful measures of assemblage quality and response to chemical, physical, and biological influences and perturbations. This has been demonstrated for a wide variety of human impacts including water pollution, habitat and flow alterations, and land use changes. Successfully applying this protocol to large rivers involves taking the correct sequence of steps in the initial development of sampling
Journal of Applied Ecology, 2006
1The need for sensitive biological measures of aquatic ecosystem integrity applicable at large spatial scales has been highlighted by the implementation of the European Water Framework Directive. Using fish communities as indicators of habitat quality in rivers, we developed a multi-metric index to test our capacity to (i) correctly model a variety of metrics based on assemblage structure and functions, and (ii) discriminate between the effects of natural vs. human-induced environmental variability at a continental scale.2Information was collected for 5252 sites distributed among 1843 European rivers. Data included variables on fish assemblage structure, local environmental variables, sampling strategy and a river basin classification based on native fish fauna similarities accounting for regional effects on local assemblage structure. Fifty-eight metrics reflecting different aspects of fish assemblage structure and function were selected from the available literature and tested for their potential to indicate habitat degradation.3To quantify possible deviation from a ‘reference condition’ for any given site, we first established and validated statistical models describing metric responses to natural environmental variability in the absence of any significant human disturbance. We considered that the residual distributions of these models described the response range of each metric, whatever the natural environmental variability. After testing the sensitivity of these residuals to a gradient of human disturbance, we finally selected 10 metrics that were combined to obtain a European fish assemblage index. We demonstrated that (i) when considering only minimally disturbed sites the index remains invariant, regardless of environmental variability, and (ii) the index shows a significant negative linear response to a gradient of human disturbance.4Synthesis and applications. In this reference condition modelling approach, by including a more complete description of environmental variability at both local and regional scales it was possible to develop a novel fish biotic index transferable between catchments at the European scale. The use of functional metrics based on biological attributes of species instead of metrics based on species themselves reduced the index sensitivity to the variability of fish fauna across different biogeographical areas.The need for sensitive biological measures of aquatic ecosystem integrity applicable at large spatial scales has been highlighted by the implementation of the European Water Framework Directive. Using fish communities as indicators of habitat quality in rivers, we developed a multi-metric index to test our capacity to (i) correctly model a variety of metrics based on assemblage structure and functions, and (ii) discriminate between the effects of natural vs. human-induced environmental variability at a continental scale.Information was collected for 5252 sites distributed among 1843 European rivers. Data included variables on fish assemblage structure, local environmental variables, sampling strategy and a river basin classification based on native fish fauna similarities accounting for regional effects on local assemblage structure. Fifty-eight metrics reflecting different aspects of fish assemblage structure and function were selected from the available literature and tested for their potential to indicate habitat degradation.To quantify possible deviation from a ‘reference condition’ for any given site, we first established and validated statistical models describing metric responses to natural environmental variability in the absence of any significant human disturbance. We considered that the residual distributions of these models described the response range of each metric, whatever the natural environmental variability. After testing the sensitivity of these residuals to a gradient of human disturbance, we finally selected 10 metrics that were combined to obtain a European fish assemblage index. We demonstrated that (i) when considering only minimally disturbed sites the index remains invariant, regardless of environmental variability, and (ii) the index shows a significant negative linear response to a gradient of human disturbance.Synthesis and applications. In this reference condition modelling approach, by including a more complete description of environmental variability at both local and regional scales it was possible to develop a novel fish biotic index transferable between catchments at the European scale. The use of functional metrics based on biological attributes of species instead of metrics based on species themselves reduced the index sensitivity to the variability of fish fauna across different biogeographical areas.
2006
The need for sensitive biological measures of aquatic ecosystem integrity applicable at large spatial scales has been highlighted by the implementation of the European Water Framework Directive. Using fish communities as indicators of habitat quality in rivers, we developed a multi-metric index to test our capacity to (i) correctly model a variety of metrics based on assemblage structure and functions, and (ii) discriminate between the effects of natural vs. human-induced environmental variability at a continental scale. 2. Information was collected for 5252 sites distributed among 1843 European rivers. Data included variables on fish assemblage structure, local environmental variables, sampling strategy and a river basin classification based on native fish fauna similarities accounting for regional effects on local assemblage structure. Fifty-eight metrics reflecting different aspects of fish assemblage structure and function were selected from the available literature and tested for their potential to indicate habitat degradation. 3. To quantify possible deviation from a 'reference condition' for any given site, we first established and validated statistical models describing metric responses to natural environmental variability in the absence of any significant human disturbance. We considered that the residual distributions of these models described the response range of each metric, whatever the natural environmental variability. After testing the sensitivity of these residuals to a gradient of human disturbance, we finally selected 10 metrics that were combined to obtain a European fish assemblage index. We demonstrated that (i) when considering only minimally disturbed sites the index remains invariant, regardless of environmental variability, and (ii) the index shows a significant negative linear response to a gradient of human disturbance. 4. Synthesis and applications . In this reference condition modelling approach, by including a more complete description of environmental variability at both local and regional scales it was possible to develop a novel fish biotic index transferable between catchments at the European scale. The use of functional metrics based on biological attributes of species instead of metrics based on species themselves reduced the index sensitivity to the variability of fish fauna across different biogeographical areas.
Fish as indicators for the assessment of the ecological integrity of large rivers
2000
Fish communities in large rivers are characterized by a high diversity, which reflects the structural diversity and habitat richness of inshore zones and connected floodplains. The connectivity of the different habitat elements in a broad spatio-temporal context, i.e., at various scales from catchment to microhabitat -and their nestednessdefine the fitness of fish species both on the individual level (e.g., growth performances) and population level (i.e., population structure, mortality, etc.). Relevant spatial scales can be the whole river course in the case of some anadromous migrators or the availability of complementary microhabitat elements, e.g., during the early ontogeny of a species. The significance of connectivity at various scales from whole river to local reach have to be evaluated based on the requirements, reaction norms, and ecological flexibility of individual species. Integrity has to be evaluated in several respects:
Fisheries Management and Ecology, 2007
The objective was to develop spatially based (type-specific) methods to assess the ecological status of European rivers according to the EU Water Framework Directive. Some 15 000 samples from about 8000 sites were pre-classified within a five-tiered classification system based on hydromorphological and physico-chemical pressures. The pre-classification was used to identify reference conditions and to calibrate the assessment methods. Clustering reference sites based on relative species composition resulted in 60 fish assemblage types within 11 of the ecoregions under study. Discriminant function analyses (DFAs) were employed to identify environmental parameters characterising fish assemblage types; altitude, river slope, wetted width, mean air temperature and distance from source were the principal predictors. These environmental parameters were used to assign impacted sites with altered fish assemblage composition to the reference fish assemblage type. Metrics (fish assemblage descriptors) responding to human pressures were selected based on correlation and DFAs. Assessment methods were developed for 43 fish assemblage types. Metrics based on individual sentinel species were more often used in type-specific methods than metrics related to reproduction, habitat and feeding. Metrics based on long-distance migrants and potamodromous species were more sensitive to human pressures than overall composition metrics, e.g. total number of species. Only some of the tested metrics showed pressure-specific responses, i.e. reacted to one type of pressure but not to others. Insectivorous, intolerant and lithophilic species exclusively responded (decreased) to chemical and hydromorphological pressures in 14-19%. Omnivorous species was the only metric type that showed a consistent reaction (increase) to continuum disruptions in 25% of the cases. Accuracy of methods based on cross-validation with pre-classification varied between 47% and 98% (mean 81%) when contrasting calibration data set (class 1 and 2) with degraded sites (class 3, 4 and 5).
Engineering Geology for Society and Territory - Volume 3, 2014
Habitat simulation models are effective tools which can be used to estimate spatial and temporal habitat availability for aquatic organisms, and to design and evaluate habitat restoration actions. Based on the meso-scale resolution, the present work proposes two indices to evaluate the spatial and temporal alteration of instream habitats. Firstly, the Index of Habitat Quantity (I HQ) describes the relative amount of habitat loss due to flow diversion, and, secondly, the Index of Habitat Stress Days (I HSD) measures the increase of continuous duration of events when habitat bottlenecks create stress to the fauna. Two case studies from the mountainous areas of Northern Italy are presented as applicatory examples. The achieved results indicate that (i) the meso-scale can be considered an appropriate scale resolution to link fish habitat requirements to fluvial morphological characteristics, and (ii) the proposed indices are flexible tools since they can capture both spatial and temporal alterations of habitat structure and can be applied to different kind of pressures (e.g., hydropower generation, hydropeaking). Keywords Habitat indices Á Fish community Á Mountainous streams Á Hydropower 75.1 Introduction The impact of water abstractions and hydro-morphological alterations on the aquatic ecosystems can be measured by assessing the effects on the biota or on its habitats. The former is difficult to accomplish because of the following: (i) the natural biological variability can increase the uncertainty of field data; (ii) the collection of field data for some biotic component, such as fish, can be difficult due to their spatial and temporal mobility; (iii) after an hydro-morphological