Challenges in developing fish-based ecological assessment methods for large floodplain rivers

Abstract  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 standardise and calibrate sampling methods and data to enhance the potential for ecological assessment of large rivers.     

Assessing the health of European rivers using functional ecological guilds of fish communities: standardising species classification and approaches to metric selection

Abstract  The functional ecological guild approach is the cornerstone for the development of Indices of Biotic Integrity and multi-metric indices to assess the ecological status of aquatic systems. These indices combine metrics (unit-specific measures of a functional component of the fish community known to respond to degradation) into a single measure of ecological assessment. The guild approach provides an operational unit linking individual species characteristics with the community as a whole. Species are grouped into guilds based on some degree of overlap in their ecological niches, regardless of taxonomic relationships. Despite European fish species having been classified into ecological guilds, classification has not been standardised Europe-wide or within the context of classifying species into guilds from which metrics can be developed for ecological assessment purposes. This paper examines the approach used by the EU project FAME to classify European fish species into consistent ecological guilds and to identify suitable metrics as basic tools for the development of a standardised ecological assessment method for European rivers to meet the requirements of the Water Framework Directive.     

The determination of ecological status in shallow lakes — a tested system (ECOFRAME) for implementation of the European Water Framework Directive

• 1. The European Water Framework Directive requires the determination of ecological status in European fresh and saline waters. This is to be through the establishment of a typology of surface water bodies, the determination of reference (high status) conditions in each element (ecotype) of the typology and of lower grades of status (good, moderate, poor and bad) for each ecotype. It then requires classification of the status of the water bodies and their restoration to at least ‘good status’ in a specified period.
• 2. Though there are many methods for assessing water quality, none has the scope of that defined in the Directive. The provisions of the Directive require a wide range of variables to be measured and give only general guidance as to how systems of classification should be established. This raises issues of comparability across States and of the costs of making the determinations.
• 3. Using expert workshops and subsequent field testing, a practicable pan‐European typology and classification system has been developed for shallow lakes, which can easily be extended to all lakes. It is parsimonious in its choice of determinands, but based on current limnological understanding and therefore as cost‐effective as possible.
• 4. A core typology is described, which can be expanded easily in particular States to meet local conditions. The core includes 48 ecotypes across the entire European climate gradient and incorporates climate, lake area, geology of the catchment and conductivity.
• 5. The classification system is founded on a liberal interpretation of Annexes in the Directive and uses variables that are inexpensive to measure and ecologically relevant. The need for taxonomic expertise is minimized.
• 6. The scheme has been through eight iterations, two of which were tested in the field on tranches of 66 lakes. The final version, Version 8, is offered for operational testing and further refinement by statutory authorities.

Copyright © 2003 John Wiley & Sons, Ltd.     

Development of a fish-based index for the assessment of river health in Europe: the European Fish Index

Abstract  A fish-based index applicable at the pan-European scale should encompass the relative importance of regional and local factors influencing the distribution of riverine fish. An effective way of using information available from fish assemblages to establish such a multimetric index is through the use of the reference condition approach that involves testing a fish assemblage exposed to a potential stressor against a reference condition. In this study, a variety of metrics based on count and abundance data and reflecting different aspects of the fish assemblage structure and function were selected from the literature for their potential to indicate degradation. Logistic and multiple linear regression procedures were applied, using an initial data set of 1000 reference sites fairly evenly distributed across European rivers (11 countries) and defined by some easily measured regional and local characteristics, to elaborate the simplest possible response model that adequately explains the observed patterns of each metric for a given site. A final list of 10 metrics was retained and the European Fish Index was tested using new independent datasets. The advantage of the resulting index to serve as a practical technical reference for cost-effective biological assessments of lotic systems in Europe is related to its ability to encompass basins and river size, and its sensitivity to physical and chemical alteration of the river ecosystem.     

Decomposition processes in coastal lagoons and their implications for the assessment of ecological health

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A simple method for assessing minimum flows in regulated rivers: the case of sea lamprey reproduction

• 1. The sea lamprey (Petromyzon marinus) is an anadromous species that occurs in some large Iberian rivers, such as the Tagus, and their tributaries. The sea lamprey populations of the River Tagus are threatened by habitat loss and overexploitation, which means that conservation measures, including maintenance of the spawning grounds, are urgent. Habitat loss is mainly due to hydroelectric and flood‐control dams that have affected the migration and spawning habitats of anadromous species. The main objective of this study was to use a simple, cost‐effective method to assess a minimum instream flow for the regulated River Tagus. The method used was based on the wetted perimeter–discharge relationship, but accounted for the habitat requirements of spawning sea lampreys.
• 2. In 1998, a habitat survey was conducted along a 30 km segment of the River Tagus downstream from Belver Dam (the first impassable obstacle for fish movements), a stretch that includes potential habitats for spawning sea lampreys. Four spawning areas were identified, and in each one a representative reach was selected along which to collect elevation and geo‐positional data. For a range of flows from 0 to 50 m³ s^?1, hydraulic modelling and studies of spawning habitat availability were conducted, both for each reach and for the total wetted area of the four reaches.
• 3. The availability of spawning habitat was limited by flow. Results showed that the present minimum flow downstream from Belver Dam (8 m³ s^?1) is insufficient to ensure suitable habitat conditions in a significant part of the segment studied; gains in wetted usable area were more substantial with discharges of up to 20 m³ s^?1, and thus a minimum flow of 10–20 m³ s^?1 was recommended. Potential spawning habitat could be improved by increasing instream flow to at least 50 m³ s^?1. The impacts of the Belver release regime on anadromous species are discussed and a more ‘ecologically oriented’ form of water management is suggested

. Copyright © 2004 John Wiley & Sons, Ltd.     

Establishing survey and monitoring protocols for the assessment of conservation status of fish populations in river Special Areas of Conservation in the UK

• 1. Under the EC Habitats Directive (92/43/EEC), several rivers in the UK have been designated Special Areas of Conservation (SACs) because they support important populations of fish species. Several factors need to be considered when establishing survey protocols to assess the conservation status of fish species in these rivers.
• 2. It is important to understand the biology and habitat requirements of fish species and to design appropriate monitoring surveys that adequately assess the status of the fish populations. This information can, in turn, provide the basis for establishing sustainable conservation targets for specific stocks, a process known as condition assessment.
• 3. Favourable condition of fish species in SAC rivers is assessed using three criteria. The first relates to density of fish in various life stages against pre‐set targets, assuming that an appropriate number of sites is surveyed to account for natural spatial and temporal variations in fish populations. The second is evaluation of the demographic structure to demonstrate continued recruitment success. Third, by mapping the distribution of the target species in individual rivers and where favourable condition is only achieved where there has been no reduction in the distribution range river between surveys.
• 4. The framework described was developed from limited survey data. As more monitoring and assessment data become available, the threshold criteria for favourable condition for each species should be improved, and uncertainty in the procedures reduced.

Copyright © 2008 John Wiley & Sons, Ltd.     

Restriction of the circulation of small pleasure boats on the rivers of Wallonia, Belgium

The regional authorities of the Walloon Region in the south of Belgium have regulated the circulation of pleasure boats, and kayaks in particular, so as to limit the conflicts between different uses of rivers (e.g. nature conservation, recreational fishing and canoeing). The regulation was enacted in 1994, using the federal law of 1973 on nature conservation as its basis. It was made necessary by the recent and important development of river-based recreational activities and by the need to protect the aquatic environment, the rivers, and the associated fauna and flora. The limitations were determined according to season, flow and time of the day. Authorized types of boat are described in the present study, and the conditions of access to the embarkation and disembarkation sites along the rivers are set out. The limitations to canoeing were settled according to the river classification. Minimum flow rates were determined for rivers where the necessity for protection was the highest because of the very high activity of rented kayaks and the risk of overcrowding the river. An information system allows the kayak operators and the sportsmen to be informed daily on the possibilities for canoeing.     

The status of the freshwater pearl mussel Margaritifera margaritifera Linn. in Scotland

1. One hundred and sixty rivers in Scotland with historical records of freshwater pearl mussel Margaritifera margaritifera were surveyed between 1996 and 1999 for the presence of the species. 2. M. margaritifera populations were classed as either ‘extinct’ (no mussels remaining), ‘not currently viable’ (ranging from only dead shells present to no juveniles present, regardless of the number of adults found), or ‘functional’ (at least one juvenile was found, regardless of the overall numbers of adults present). 3. M. margaritifera populations could be classed as ‘functional’ in only 52 rivers (34% of total surveyed) and in only 17 of these were juveniles below 20 mm (5 yrs old) present. Furthermore, in only 10 of these functional rivers were mussels also still considered either to be common or abundant and these included both large easterly‐flowing rivers and small western rivers and streams. 4. In approximately two‐thirds (101) of the 155 rivers occupied 100 years ago, M. margaritifera is now extinct or is about to become extinct. Furthermore, analysis indicates that the rate of mussel population extinction has accelerated since 1970, with a recent average of two mussel river extinctions per year. 5. The predominant threat to the mussel populations has undoubtedly been pearl fishing. This has been occurring at every river, even in the most remote northwest areas, where most of the ‘functional’ populations remain. Recent legislation has provided full protection to M. margaritifera, so that all pearl harvesting is now illegal. 6. Locally, river engineering and host salmonid stock decline poses a serious threat and eutrophication has already eliminated populations in southern and eastern Scotland. 7. In every part of its global range, M. margaritifera has declined substantially and is now either threatened with extinction or is highly vulnerable. Based on recent estimates from across the species range, it appears that Scotland now probably holds at least half of the world's remaining functional M. margaritifera populations. Copyright © 2000 John Wiley & Sons, Ltd.     

A simple field method for assessing the ecological quality of riparian habitat in rivers and streams: QBR index

• 1. An index of riparian quality useful for the management of streams and rivers is presented. The purpose of the index is to provide managers with a simple method to evaluate riparian habitat quality. The index is easy to calculate and can be used together with any other index of water quality to assess the ecological status of streams and rivers. It may also be a useful tool for defining ‘high ecological status’ under the EC Water Framework Directive.
• 2. The index, named QBR, is based on four components of riparian habitat: total riparian vegetation cover, cover structure, cover quality and channel alterations. It also takes into account differences in the geomorphology of the river from its headwaters to the lower reaches. These differences are measured in a simple, quantitative way. The index score varies between 0 and 100 points.
• 3. The QBR index is calculated in the field through a two‐sided A4 page form that may be completed in 10 min.
• 4. The development of the QBR index included trials in four Mediterranean stream catchments in Catalonia (NE Spain). Seventy‐two sampling sites were assessed and results were used to test the index.
• 5. No taxonomic expertise is needed to apply the index, although some knowledge of local flora is required to differentiate between native and non‐native tree species.
• 6. These results show that the QBR index may be used despite regional differences in plant communities. The quality ranges obtained when the index is applied are not heavily influenced by observers at the same site.
• 7. At present, the index is being used by different research teams and tested in a comparative study of 12 watersheds along the Mediterranean Spanish coast.
• 8. It is expected that the QBR index may be adapted for use in other geographical areas in temperate and semi‐arid zones without changes in the index rationale.

Copyright © 2002 John Wiley & Sons, Ltd.     

Brook trout occupancy in rivers and streams of the Mixedwood Plains Ecozone,Ontario

Brook trout (Salvelinus fontinalis) are an iconic freshwater salmonid native to northeastern North America. They prefer cold, clean rivers and lakes, and have been culturally, socially and economically valued for decades. Overharvest and deforestation associated with European settlement in southern Ontario, Canada led to notable declines in brook trout abundance in rivers and streams by the late 1800s. Today, they are threatened by further habitat degradation, non-native species, and climate change. In this study, we document brook trout occupancy in rivers and streams of the Mixedwood Plains Ecozone in southern Ontario, between 1970–1980 and 2000–2010. We used generalised linear models to determine occupancy variation between the two time periods at five spatial scales spanning multiple watershed levels. We detected a decline in occupancy between time periods for the tertiary (from 23% to 17%) and quaternary (from 35% to 22%) watershed scales. In the Credit River-Sixteen Mile Creek watershed, mean occupancy decreased to a third of past estimate (from 31% to 10%). For a subset of 86 sites with overlapping sampling in both periods no temporal trend was detected, but a post-hoc analysis indicated low statistical power (0.07), which suggested that more intensive sampling would be needed to better quantify brook trout occupancy changes at this scale. The occupancies quantified for the past period in our study may serve as benchmarks for brook trout restoration efforts.     

Development and assessment of habitat suitability criteria for adult brown trout in southern New England rivers

Abstract –  Habitat suitability criteria (HSC) for depth, mean velocity, nose velocity, substrate, embeddedness, and cover were developed for brown trout ≥170 mm ( Salmo trutta Linnaeus) on the West Branch Farmington River, CT, USA. Microhabitat data was collected by underwater observation using an equal effort habitat sampling design; HSC were constructed using nonparametric tolerance limits. Transferability of previously published HSC to the West Branch Farmington River was poor; only 1 of 13 HSC tested was considered transferable. The HSC developed for the West Branch Farmington River were tested for transferability to the East Branch Westfield River, Massachusetts. First, a composite suitability index (SI) score was calculated using the source HSC for each occupied and unoccupied location in the Westfield River. Then, χ ²-tests were used to determine if optimal or suitable locations were occupied in greater proportion than usable or unsuitable locations. Composite SI scores based on total depth, mean velocity, and cover were not transferable, but composite SI scores based only on total depth and mean velocity were. A multivariate profile analysis was also used to test for transferability. In each test, only total depth, fish depth, and mean velocity HSC were successfully transferred. Transferability of depth and velocity HSC between rivers shows promise for applications to similar systems where brown trout occur.     

Recovery and re-establishment of Atlantic salmon, Salmo salar, in limed Norwegian rivers

A total of 21 acidified Norwegian rivers are now being limed to re‐establish or restore Atlantic salmon, Salmo salar L., stocks. Natural reproduction of Atlantic salmon was evident 1 year after the first year of liming in all rivers that had lost their native stocks (n = 9) except for one river. The density of fry (age 0+) developed significantly more rapidly in rivers that supported remnant stocks than in rivers that had lost their stocks, based on data 5 years after treatment. Nine of the study rivers were supplied with hatchery‐reared salmon, mainly unfed fry. Of the rivers with lost stocks, those which were supplied with fish had significantly higher densities than those that were not enhanced. On the other hand, rivers with remnant stocks that were supplied with fish had significantly lower densities of salmon fry than those that did not undergo such mitigation measures. In 2001, all limed rivers yielded 41.9 t of salmon.     

天津市河流和水库浮游植物群落与水环境因子关系的研究

为探明天津市河流、水库浮游植物群落结构及其与环境因子的关系,于2009年5月、7月、9月对天津市的5条河流和4个水库进行采样分析。结果表明,天津市河流浮游植物为7门100种,优势种为绿藻、蓝藻;水库为8门81种,优势种为硅藻、蓝藻。环境因子在河流和水库间差异极显著的为透明度、pH、总磷和重碳酸盐碱度(P<0.01)。影响浮游植物群落结构的环境因子,河流依次为:浮游动物丰度、高锰酸盐指数、氨氮、碳酸盐碱度、磷酸盐浓度、总磷;水库依次为:重碳酸盐碱度、钙离子浓度、氨氮、透明度、溶解氧、水深、叶绿素(a、b)、总碱度、总硬度、pH。     

Typology of historical sources and the reconstruction of long‐term historical changes of riverine fish: a case study of the Austrian Danube and northern Russian rivers

Historical data are widely used in river ecology to define reference conditions or to investigate the evolution of aquatic systems. Most studies rely on printed documents from the 19th century, thus missing pre‐industrial states and human impacts. This article discusses historical sources that can be used to reconstruct the development of riverine fish communities from the Late Middle Ages until the mid‐20th century. Based on the studies of the Austrian Danube and northern Russian rivers, we propose a classification scheme of printed and archival sources and describe their fish ecological contents. Five types of sources were identified using the origin of sources as the first criterion: (i) early scientific surveys, (ii) fishery sources, (iii) fish trading sources, (iv) fish consumption sources and (v) cultural representations of fish. Except for early scientific surveys, all these sources were produced within economic and administrative contexts. They did not aim to report about historical fish communities, but do contain information about commercial fish and their exploitation. All historical data need further analysis for a fish ecological interpretation. Three case studies from the investigated Austrian and Russian rivers demonstrate the use of different source types and underline the necessity for a combination of different sources and a methodology combining different disciplinary approaches. Using a large variety of historical sources to reconstruct the development of past fish ecological conditions can support future river management by going beyond the usual approach of static historical reference conditions.     

Trophic status of rivers in the Forth catchment,Scotland

1. An increase in nutrient concentrations in fresh water may pose a threat to water quality, biodiversity, and the uses to which these resources are subject. Compared with standing waters, the trophic status of running water has been neglected with few studies describing the extent of eutrophication in rivers. 2. This paper uses a range of information, including chemical analysis, subjective measures of algal abundance, and professional assessments to describe the trophic status of rivers in the Forth catchment, central Scotland. The importance of ‘low level’ data for achieving a wide geographical cover is emphasized. 3. Information collected between 1985 and 1994, now held by the Scottish Environment Protection Agency, was used to create a river classification scheme which allows the definition of trophic status using data on soluble reactive phosphorus concentration and algal abundance. Two thirds of the 3250 km of river were classified, showing that 74% of the river length had low nutrient concentrations and were defined as oligotrophic or mesotrophic. 4. Diffuse sources of phosphorus were found to be the most important factor determining the trophic status of rivers, with 71% of the river length controlled by diffuse inputs and only 7% by point sources. The importance of point sources increased with eutrophication; however, even in the most enriched category, point sources were thought to dominate the supply of nutrients in only 34% of the river length. © 1997 John Wiley & Sons, Ltd.