bluuebunny/crossref_metadata_2025_split huggingface dataset:
River regulation and fish larvae: variation through space and time
Authors: HUMPHRIES PAUL , SERAFINI LUCIANO G. , KING ALISON J. 
Published: March 2003

1. Patterns in abundance and distribution of larval fish in a heavily regulated and a mildly regulated Australian lowland river were compared over four breeding seasons to gain some insight into how river regulation affects fish populations.2. Larvae from a total of 13 species from nine families were recorded from the two rivers. The mildly regulated Broken River supported twice as many species as the heavily regulated Campaspe River. The two rivers shared three introduced species but only two native species. The dominant species in the Campaspe was not found in the Broken River.3. The two most abundant species in the Campaspe were classified as `opportunists'. They are small, short‐lived species, which spawn for up to 9 months, encompassing extremes in temperature and flow. The extended spawning period may place a subset of larvae in optimal conditions for recruitment and is hypothesised as being the key to the success of these species.4. Most species spawned each year, despite large interannual variation in flow and temperature conditions. Poor recruitment over several decades, rather than a failure to spawn, is considered the most likely explanation for differences in the larval fish faunas between the two rivers.5. The highly regulated section of the Campaspe River downstream of the regulating impoundment is thought to provide suboptimal habitat conditions for larvae relative to the less regulated downstream sections.6. The timing of occurrence of larvae of the dominant species varied by breeding season and may be the result of flexibility in the timing of spawning.
Development and validation of a fish‐based index for the assessment of ‘river health’ in France
Authors: Oberdorff Thierry , Pont Didier , Hugueny Bernard , Porcher Jean‐Pierre 
Published: March 2003

SUMMARY 1. In Europe, water policy is currently undergoing considerable change as emphasised by the recent European Water Framework Directive (WFD), which requires the restoration and maintenance of ‘healthy’ aquatic ecosystems by the assessment of their hydromorphological, chemical and biological characteristics. If the requirements of the WFD are to be met, effective biological tools are needed to measure the ‘health’ of rivers at scales large enough to be useful for management. These tools need to be ecologically based, efficient, rapid and applicable in different ecological regions. Among potential indicators, fish assemblages are of particular interest because of their ability to integrate environmental variability at different spatial scales. To meet the goals of the WFD, the French Water Agencies and the Ministry of the Environment initiated a research programme to develop a fish‐based index that would be applicable nationwide.2. A variety of metrics based on occurrence and abundance data and reflecting different aspects of the fish assemblage structure and function were selected from available literature and for their potential to indicate degradation.3. Logistic and multiple linear regression procedures were applied, using an initial data set of 650 reference sites fairly evenly distributed across French rivers and defined by some easily measured regional and local characteristics, to elaborate the simplest possible response model that adequately explained the observed patterns of each metric for a given site.4. Models obtained for each metric were validated using two independent data sets of 88 reference sites and 88 disturbed sites. These procedures allowed us to select the most effective metrics in discriminating between reference and disturbed sites.
Sampling variation in macroinvertebrate data and implications for river quality indices
Authors: Clarke R. T. , Furse M. T. , Gunn R. J. M. , Winder J. M. , Wright J. F. 
Published: March 2003

SUMMARY 1. The EC Water Framework Directive (2000/60/EC) recognises the need for biological monitoring. Indices derived from standard samples of macroinvertebrates are frequently used for the appraisal of the ecological quality of rivers. However, information on the errors or chance variation that can influence the value of an index is also important.2. This paper describes a study to quantify the observed sampling variation in three ecological indices based on the Biological Monitoring Working Party (BMWP) score system across a wide range of river types and qualities. The indices are number of BMWP taxa, BMWP score and Average Score Per Taxon (ASPT).3. The study sites were selected to encompass the four major groups within the River InVertebrate Prediction And Classification System (RIVPACS) site classification for Britain. Within each group, four sites which differed in ecological quality grade were chosen (total of 16 sites). At each site three standard RIVPACS samples were taken in each of spring, summer and autumn by trained staff. In each season, two samples were taken by one biologist and the third by a different individual to allow for within and between‐operator variation.4. The effects of sampling variation within a season on the number of taxa, BMWP score and ASPT across all sites, irrespective of operator, could be represented by some simple parameters. We found that the sampling SD of the square root of the number of taxa, square root of BMWP score and the untransformed ASPT were roughly constant in each case, irrespective of site type or quality. For each index, SD for two and three seasons combined samples were smaller than for single season samples.5. Inter‐operator influences on sample values were negligible (4–12% of total sampling SD) in this study. This underlines the importance of adequate training for all staff involved in extensive monitoring programmes which use standard procedures from one year to the next, but may involve different staff.6. Indices for number of taxa, BMWP score and ASPT were all estimated with greater precision from combined season samples than from the averages of two or three seasons' samples.7. This study enables us to estimate confidence intervals for the values of the number of taxa, BMWP score and ASPT based on single season, two or three season combined samples collected using standard RIVPACS procedures for any river site in Britain. The results can also be used in simulation models which incorporate the effects of sampling variation into assessments of the ecological quality of river sites based on the ratio of observed to RIVPACS expected values of these BMWP indices.
Riverine landscape diversity
Authors: WARD J. V. , TOCKNER K. , ARSCOTT D. B. , CLARET C. 
Published: March 2003

1. This review is presented as a broad synthesis of riverine landscape diversity, beginning with an account of the variety of landscape elements contained within river corridors. Landscape dynamics within river corridors are then examined in the context of landscape evolution, ecological succession and turnover rates of landscape elements. This is followed by an overview of the role of connectivity and ends with a riverine landscape perspective of biodiversity.2. River corridors in the natural state are characterised by a diverse array of landscape elements, including surface waters (a gradient of lotic and lentic waterbodies), the fluvial stygoscape (alluvial aquifers), riparian systems (alluvial forests, marshes, meadows) and geomorphic features (bars and islands, ridges and swales, levees and terraces, fans and deltas, fringing floodplains, wood debris deposits and channel networks).3. Fluvial action (erosion, transport, deposition) is the predominant agent of landscape evolution and also constitutes the natural disturbance regime primarily responsible for sustaining a high level of landscape diversity in river corridors. Although individual landscape features may exhibit high turnover, largely as a function of the interactions between fluvial dynamics and successional phenomena, their relative abundance in the river corridor tends to remain constant over ecological time.4. Hydrological connectivity, the exchange of matter, energy and biota via the aqueous medium, plays a major though poorly understood role in sustaining riverine landscape diversity. Rigorous investigations of connectivity in diverse river systems should provide considerable insight into landscape‐level functional processes.5. The species pool in riverine landscapes is derived from terrestrial and aquatic communities inhabiting diverse lotic, lentic, riparian and groundwater habitats arrayed across spatio‐temporal gradients. Natural disturbance regimes are responsible for both expanding the resource gradient in riverine landscapes as well as for constraining competitive exclusion.6. Riverine landscapes provide an ideal setting for investigating how complex interactions between disturbance and productivity structure species diversity patterns.
Aquatic invertebrates in riverine landscapes
Authors: MALMQVIST BJÖRN 
Published: March 2003

1. Riverine systems consist of a mosaic of patches and habitats linked by diverse processes and supporting highly complex communities. Invertebrates show a high taxonomic and functional diversity in riverine systems and are in several ways important components of these systems. Their distribution patterns, movements and effects on ecological flows, testify to their importance in various landscape ecological processes. This paper reviews the invertebrate literature with respect to patterns and processes in the riverine landscape.2. The distribution of invertebrates in riverine habitats is governed by a number of factors that typically act at different scales. Hence, the local community structure can be seen as the result of a continuous sorting process through environmental filters ranging from regional or catchment‐wide processes, involving speciation, geological history and climate, to the small‐scale characteristics of individual patches, such as local predation risk, substratum porosity and current velocity.3. Dispersal is an important process driving invertebrate distribution, linking different ecological systems across boundaries. Dispersal occurs within the aquatic habitat as well as into the terrestrial surrounding, and also over land to other waterbodies. New genetic techniques have contributed significantly to the understanding of aquatic invertebrate dispersal and revealed the importance of factors such as physical barriers, synchrony of emergence and taxonomic affiliation.4. Invertebrates affect the cycling of nutrients and carbon by being a crucial intermediate link between primary producers, detritus pools or primary consumers, and predators higher up in the trophic hierarchy. Suspension feeders increase the retention of carbon. The subsidies of aquatic invertebrates to the terrestrial ecosystem have been shown to be important, as are reciprocal processes such as the supply of terrestrial invertebrates that fall into the water.5. Future studies are needed both to advance theoretical aspects of landscape ecology pertaining to the invertebrates in riverine systems and to intensify the experimental testing of hypotheses, for example with respect to the scaling of processes and to linkages between the terrestrial and aquatic systems. Another promising avenue is to take advantage of naturally steep environmental gradients, and of systems disturbed by humans, such as regulated rivers. By comparison with unimpaired reference sites, the mechanisms involved might be identified. The use of `natural' experiments, especially where environmental gradients are steep, is another technique with great potential.
Genetic population structure and dispersal in Atlantic Island caddisflies
Authors: Kelly Lucy C. , Rundle Simon D. , Bilton David T. 
Published: March 2003

SUMMARY 1. Population genetic structure of Wormaldia tagananana, a caddis with a narrow geographic range and endemic to the Canary Islands, was investigated by studying allozyme variation at 11 putative loci in five of the eight extant populations on Tenerife and La Gomera. Genetic variability, population structure and gene flow were compared with those reported previously in more widespread Trichoptera, particularly Canarian populations of the non‐endemic limnephilid Mesophylax aspersus, to examine the hypothesis that the Wormaldia, with its restricted range, would exhibit relatively little genetic variability and gene flow.2. Despite it being a narrow‐range island endemic, genetic variability in populations of W. tagananana is broadly similar to values reported for more widespread caddis.3. Significant genetic population structure was observed in W. tagananana (overall FST = 0.387), greater than that seen in M. aspersus and amongst the highest reported for lotic caddis to date. Several site‐ and island‐specific alleles were reported, providing further evidence for the relative isolation of individual Wormaldia populations.4. Significant deviations from Hardy–Weinberg equilibrium were found in four of five populations (overall FIS = 0.675). This could result from within‐locality population substructuring, or offspring within a reach being the product of a limited number of matings.5. This genetic evidence supports the hypothesis that the restricted range of W. tagananana is, at least in part, because of limited dispersal ability.
Riverine landscapes: an introduction
Authors: TOCKNER K. , WARD J. V. , EDWARDS P. J. , KOLLMANN J. 
Published: March 2003

1. This paper is an introduction to a special issue of Freshwater Biology containing selected papers from the First International Symposium on Riverine Landscapes held in March 2001 in Switzerland.2. The primary goal of the symposium was to synthesise present understanding of riverine landscapes from the perspectives of different disciplines. A landscape approach was used to address interactions between patterns and processes, in the context of spatial heterogeneity, across scales in physical and biological systems.3. The three main themes were: (i) hydrogeomorphic processes, (ii) biological dynamics and (iii) human influences in riverine landscapes.
A comparison of statistical approaches for modelling fish species distributions
Authors: Olden Julian D. , Jackson Donald A. 
Published: March 2003

SUMMARY1. The prediction of species distributions is of primary importance in ecology and conservation biology. Statistical models play an important role in this regard; however, researchers have little guidance when choosing between competing methodologies because few comparative studies have been conducted.2. We provide a comprehensive comparison of traditional and alternative techniques for predicting species distributions using logistic regression analysis, linear discriminant analysis, classification trees and artificial neural networks to model: (1) the presence/absence of 27 fish species as a function of habitat conditions in 286 temperate lakes located in south‐central Ontario, Canada and (2) simulated data sets exhibiting deterministic, linear and non‐linear species response curves.3. Detailed evaluation of model predictive power showed that approaches produced species models that differed in overall correct classification, specificity (i.e. ability to correctly predict species absence) and sensitivity (i.e. ability to correctly predict speciespresence) and in terms of which of the study lakes they correctly classified. Onaverage, neural networks outperformed the other modelling approaches, although all approaches predicted species presence/absence with moderate to excellent success.4. Based on simulated non‐linear data, classification trees and neural networks greatly outperformed traditional approaches, whereas all approaches exhibited similar correct classification rates when modelling simulated linear data.5. Detailed evaluation of model explanatory insight showed that the relative importance of the habitat variables in the species models varied among the approaches, where habitat variable importance was similar among approaches for some species and very different for others.6. In general, differences in predictive power (both correct classification rate and identity of the lakes correctly classified) among the approaches corresponded with differences in habitat variable importance, suggesting that non‐linear modelling approaches (i.e. classification trees and neural networks) are better able to capture and model complex, non‐linear patterns found in ecological data. The results from the comparisons using simulated data further support this notion.7. By employing parallel modelling approaches with the same set of data and focusing on comparing multiple metrics of predictive performance, researchers can begin to choose predictive models that not only provide the greatest predictive power, but also best fit the proposed application.
Biomanipulation of lake ecosystems: an introduction
Authors: Kasprzak P. , Benndorf J. , Mehner T. , Koschel R. 
Published: March 2003

SUMMARY 1. This paper is an introduction to a special issue of Freshwater Biology containing selected papers from an international symposium on Food Web Effects of Fish in Lake Ecosystems: Research Progress, Water Quality and Fisheries Management held from 31 May to 3 June 2000 in Rheinsberg, Germany. The primary goal of the workshop was to enlarge the current view of fish‐induced effects on lake ecosystems. An additional goal was to promote biomanipulation as a multiple‐use tool for managing freshwater ecosystems.2. The three main topics addressed at the workshop were: (i) mechanisms involved in biomanipulation, (ii) whole‐lake case studies and (iii) management aspects in water quality and fisheries.3. Mortality of Daphnia, nutrient recycling, habitat selection and fish predation are reported as important mechanisms governing food‐web effects as a result of biomanipulation.4. Whole‐lake case studies indicate that repeated fish removal can help improve water quality of shallow lakes, but successful biomanipulation of deep, thermally stratifying lakes remains difficult.5. In many cases, biomanipulation of lakes has proved to provide benefits in addition to improving water quality. As all lake users are potentially affected when biomanipulation is used as a lake management tool, their concerns need to be clearly recognised if biomanipulation is to be successful in practice.
Hypolimnetic anoxia hampers top–down food‐web manipulation in a eutrophic lake
Authors: Dawidowicz Piotr , Prejs Andrzej , Engelmayer Andrzej , Martyniak Andrzej , Kozłowski Jacek , Kufel Lech , Paradowska Małgorzata 
Published: March 2003

SUMMARY 1. A biomanipulation experiment was carried out in a small (10 ha), but relatively deep (17 m) and highly eutrophic lake in northern Poland. The lake had been stocked in 1996, 1997 and 1998 with a variety of piscivorous fish (pike, catfish, trout and pikeperch), in order to reduce numbers of cyprinid planktivores.2. Piscivore stocking was associated with a threefold decrease in the offshore fish density (night echosounding). Despite this reduction, the large planktonic cladoceran, Daphnia hyalina, remained scarce, whereas the density of small‐sized zooplankton increased greatly.3. The lack of demographic response in D. hyalina was probably due to the anoxia in the hypolimnetic refuge of this vertically migrating species. The anoxic hypolimnion, below 3–4 m depth, was inhabited day and night by numerous Chaoborus flavicans larvae.4. Changes in zooplankton were associated with shifts in the taxonomic composition (from single‐cell green algae to filamentous cyanobacteria), size structure (from nano‐ to net phytoplankton) and seasonal dynamics of phytoplankton, but not in the average biomass of planktonic algae. A clear‐water phase, which was absent in the prestocking years, developed in spring, with Secchi depth reaching 2.5 m, a value which had never been recorded in the 20 years preceding the biomanipulation. In general, the lake's status was switched from hypertrophic to eutrophic.5. Deteriorating food conditions, resulting from qualitative changes in the phytoplankton community, combined with predation pressure by the remaining fish and Chaoborus larvae were associated with the ultimate elimination of D. hyalina from the lake.
Genetic population structure of the net‐winged midge, Elporia barnardi (Diptera: Blephariceridae) in streams of the south‐western Cape, South Africa: implications for dispersal
Authors: Wishart M. J. , Hughes J. M. 
Published: March 2003

SUMMARY 1. The net‐winged midges (Diptera: Blephariceridae), with highly specific habitat requirements and specialised morphological adaptations, exhibit high habitat fidelity and a limited potential for dispersal. Given the longitudinal and hierarchical nature of lotic systems, along with the geological structure of catchment units, we hypothesise that populations of net‐winged midge should exhibit a high degree of population sub‐structuring.2. Sequence variation in the cytochrome c oxidase subunit I (COI) region of the mitochondrial DNA (mtDNA) was examined to determine patterns of genetic variation and infer historical and contemporary processes important in the genetic structuring of populations of Elporia barnardi. The DNA variation was examined at sites within streams, between streams in the same range, and between mountain ranges in the south‐western Cape of South Africa.3. Twenty‐five haplotypes, 641 bp in length, were identified from the 93 individuals sampled. A neighbour‐joining tree revealed two highly divergent clades (∼5%) corresponding to populations from the two mountain ranges. A number of monophyletic groups were identified within each clade, associated with individual catchment units.4. The distribution of genetic variation was examined using analysis of molecular variance (amova). This showed most of the variation to be distributed among the two ranges (∼80%), with a small percentage (∼15%) distributed among streams within each range. Similarly, variation among streams on Table Mountain was primarily distributed among catchment units (86%). A Mantel's test revealed a significant relationship between genetic differentiation and geographical distance, suggesting isolation by distance (P < 0.001).5. Levels of sequence divergence between the two major clades, representing the two mountain ranges, are comparable with those of some intra‐generic species comparisons. Vicariant events, such as the isolation of the Peninsula mountain chain and Table Mountain, may have been important in the evolution of what is now a highly endemic fauna.6. The monophyletic nature of the catchment units suggests that dispersal is confined to the stream environment and that mountain ridges provide effective physical barriers to dispersal of E. barnardi.