bluuebunny/crossref_metadata_2025 huggingface dataset:
A review of the effect of river regulation on mayflies (Ephemeroptera)
Authors: Brittain John E. , Saltveit Svein Jakob
Published: February 2007

Impoundment and diversion of watercourses for power production and water supply can have profound effects on the mayfly fauna. To explain such effects a species‐specific approach is adopted on account of differing habitat requirements and life histories in the order and even within genera. Environmental conditions such as discharge and flow patterns, temperature, food availability, and predation may be changed. This leads to changes in the density and species composition of the mayfly community, especially when there is a hypolimnion drain from reservoirs. Temperature changes below such reservoirs may remove obligatory life cycle thresholds. Prolonged periods of low discharge lead to the dominance of genera, such as Paraleptophlebia, Choroterpes, Siphlonurus, and Pseudocloen, typical of slow‐flowing and lentic habitats.

The life cycle plasticity and opportunism shown by Baetis rhodani in Europe and B. tricaudatus in North America have undoubtedly contributed to their success in regulated rivers. The life history characteristics of Tricorythodes are also advantageous below dams. The increased growth of periphyton and mosses below many dams favour certain Ephemerellidae, but restrict or eliminate many Heptageniidae. In order to survive adverse conditions, flexible life cycles or a short period of rapid nymphal growth coupled with a long period of egg development, are advantageous.
Removal of brown trout (Salmo trutta L): Changes in population dynamics in a weir basin in Western Norway
Authors: Raddum Gunnar G. , Fjellheim Arne , Sægrov Harald
Published: February 2007

The trout population in a 10.6 ha weir basin in western Norway has been studied over thirteen years. Baseline investigations were carried out during 1974–78, three to five years after construction of the weir. Studies in 1983 showed dominance of the 1977 and 1978 year‐classes. This dominance lasted until 1985. Removal of 75 per cent of the population for stocking in reservoirs reduced the fish biomass from 1.43 to 0.28 kg 100 m−2. This increased the growth rate and condition factor of the remaining fish in subsequent years. The trout enter the basin mainly at age 2+ and 3+. No increase in the number of immigrants was observed during the first two years after removal of fish. In the third year, however, a five‐fold increase was measured. Most of these fish belonged to the 1985 year‐class, which had little contact with the strong classes of 1977 and 1978. We conclude that density‐dependent factors control immigration to the basin, whereas a combination of density‐dependent and independent factors act on the recruitment in the riffle areas. We suggest that the highest recruitment of fish is obtained by reducing the density‐dependent effect through removing a very high proportion of the young fish, 2+ and 3+, every year.
Effects of stream regulation on atlantic salmon, Salmo salar L., and brown trout, Salmo trutta l., in the upper severn catchment, U.K.
Authors: Cowx I. G. , Gould R. A.
Published: February 2007

Data for three rivers in the upper Severn catchment are examined to assess the influence of regulation strategies on the Atlantic salmon and brown trout populations. In the regulated Afon Clywedog, juvenile recruitment of both species declined steadily following increased utilization of the impoundment for regulation. The decline was considered the response to the variable and rapidly changing discharge regime adopted in the river. Spawning success and juvenile survival of salmonids in the Vyrnwy was relatively stable suggesting the flow regime in this river was less devastating.
Effects of river regulation on the structure of a fast‐growing brown trout (Salmo trutta L.) population
Authors: Aass Per , Nielsen Per Sondrup , Brabrand Åge
Published: February 2007

During the last 70 years, the Norwegian lake Mjøsa and its inflowing rivers have been subjected to serious changes due to hydroelectric power development. Regulation of the main inlet river, Gudbrandsdalslagen, started in 1919. The river power station at the Hunder fall was completed in 1964. This resulted in a reduction of winter water flow below the Hunder dam from approximately 26m3s−1 to 2m3s−1, which affected the most important spawning area of the fast‐growing population of brown trout, Salmo trutta L. The population was investigated in detail in 1907, 1909, 1961, and 1985, and river growth, smolt age, and growth in Lake Mjøsa are compared. Only wild fish were included in the study. The main pattern throughout this period shows an increased river growth rate before smoltification and reduced smolt age. The average smolt age dropped from 4.7 years in 1909 to 4.1 years in 1985, and at the same time smolt size decreased from 26.8 cm to 25.1 cm. Considering the major changes in abiotic factors in the river spawning section, the changes in age structure and growth of brown trout smolt are comparatively small.

In Lake Mjøsa, increased productivity due to input of nutrients has obviously favoured forage fish such as smelt (Osmerus eperlanus (L.)) and vendace (Coregonus albula (L.)). The growth rate of brown trout in the lake has improved from 1909 to 1961 and 1985, followed by a reduced spawning age. However, due to increased human exploitation the average length of ascending fish (approximately 68 cm) and condition factor ( K = 1.14–1.16) have altered little.
Ability of phabsim to predict chinook salmon spawning habitat
Authors: Shirvell C. S.
Published: February 2007

PHABSIM, part of the Instream Flow Incremental Methodology, was used to predict the spawning habitat used by chinook salmon in a 600 m long section of the Nechako River, British Columbia, Canada. Predictions of the model were compared to the location and amount of habitat actually used by adult chinook salmon in 1974, 1980, and 1986. About 3800 m2 (70 per cent) of the spawning area actually used by the population were predicted as unusable by the ‘best’ prediction, while 87 per cent of the area predicted as usable has never had recorded use. The ‘best’ prediction resulted from using close transect spacing, frequent measurements along the transect, river‐specific habitat suitability criteria, and modelling habitat at the fish's position near the stream bottom. Depending upon the spacing of the transects and the habitat suitability criteria used, PHABSIM predicted 210 per cent to 660 per cent more spawning habitat was available than historically had ever been used. Chinook salmon in the Nechako River spawn mainly on the upstream face of dunes, therefore, the assumption in PHABSIM that conditions predicted at the transects remain unchanged upstream and downstream part way to the adjacent transects was false. This assumption resulted in about two‐thirds of the correct predictions being made for the wrong reason. The accuracy of PHABSIM's predictions for spawning might be improved by incorporating an index of river bottom topography or velocity gradient into the model.
An analysis of brown trout (Salmo trutta fario L.) habitat: The role of qualitative data from expert advice in formulating probability‐of‐use curves
Authors: Chaveroche P. , Sabaton C.
Published: February 2007

To study the preferred habitat of brown trout, a group of fifteen experts met in the Tarn départment to answer a questionnaire relating to 200 sampled points on the Agout river. The experts were requested to give their opinion on the suitability of various habitats, defined by velocity, depth, substrate, presence of covers, etc. for trout—at each stage of growth, fry, juvenile and adult fish—and the factors which had influenced their choice.

The analysis of these questionnaires has allowed probability‐of‐use curves to be plotted for brown trout. The agreement between the curves derived from this study and those proposed by Bovee is encouraging and gives credit to the validity of the Instream Flow Incremental Methodology. Direct analysis of the data collected has led to conclusions in agreement with the probability‐of‐use formulation and has identified the best conditions of habitat at different stages of growth of trout for a certain number of parameters. The paper proposes a factor analysis method to secure a direct estimate of the quality of a habitat defined by a group of independent parameters.
Probability‐of‐use curves applied to brown trout (Salmo trutta fario L.) in rivers of southern France
Authors: Belaud A. , Chaveroche P. , Lim P. , Sabaton C.
Published: February 2007

The aim of this paper is to illuminate any environmental preference of brown trout (Salmo trutta, fario) in streams of the South of France and, in this case, to evaluate the reliability of the Instream Flow Incremental Method, suggested by Bovee (1974) for American streams.

At various randomly distributed points on five tributaries of the Tarn and Ariège rivers the occurrence of fishes at different stages of development and selected morphodynamic characteristics (velocity, depth, substratum) were observed simultaneously. The presence of fish was checked by using two special electric fishing techniques: (1) casting the anode ahead of the operator for a sudden immobilization of fish; and (2) connecting previously immersed electrodes on the riverbed.

Curves have been plotted for velocity and depth parameters in each river at each season by analysing the frequency of appearance of fish at different stages of development in the different habitats. These curves do not vary greatly from one river to the next and the differences between seasons are not very significant. Single curves have thus been plotted by grouping the data from the different series of measurements.

The curves obtained for the velocity parameter are very close to those proposed by Bovee and reveal that the fishes have a preference for low velocities, regardless of their stage of development. As shown by the Bovee curves, the preference obtained for the depth parameter is related to the stage of development: shallow waters are much preferred by fry and juveniles but are not greatly frequented by adults. This study seems to confirm the existence of a real environmental preference among brown trout, indicating that the Instream Flow Incremental Method can be used for French 1st category streams.
Effects of river regulation on the lower Ebro river (NE Spain)
Authors: Muñoz Isabel , Prat Narcis
Published: February 2007

The regulation of the Ebro River in the 1960s has changed the discharge pattern: spring floods have been reduced and, as the reservoirs are used for hydroelectrical purposes, discharge varies daily.

The last 50 km of the river have been studied for two years (1986 and 1987). Our main purpose was to establish the particulate organic and inorganic transport of the river and its seasonal changes. Particulate material was sampled in surface and deep waters. Water conductivity ranges between 0.9 and 53 mS, and anoxia is common in summer situations. Particulate C ranges between 1 and 3 mg l−1 with higher values in summer; particulate N is very similar along the year with values between 0.1 and 0.5 mg l−1.

Effects of regulation seem to be important in supplying very high nutrient content to algae and producing a high biomass and production in the lower part of the river, especially in summer. Diatoms and Chlorophyta are the most abundant groups. Phosphorus is higher than 5 μmol l−1, with lower values in summer. Most of particulate material is very fine (between 0.45 and 50 μm). The high biomass also explains the presence of abundant filter‐feeders, such as Hydropsyche and Ephoron virgo. In some parts, where light reaches the bottom, stones and boulders are covered by Cladophora. In this case, grazers such as the gastropods Melanopsis and Theodoxus are abundant.
Process for cooperation on international river basin projects
Authors: Nagy László S.
Published: February 2007

This paper describes a process for cooperation in international river basin projects. The significance of multilateral projects is stressed and the most important tasks of common preparation are considered. The potential role of the United Nations and other international organizations are demonstrated. The example is given of the natural and economic background of the Danube River and some precedents are cited in connection with the problems of planning the Bős (Gabcikovo)‐Nagymaros Barrage Project. This project provides a good example of the way in which a general method can be adapted to international projects by the use of a suggested 33‐step scheme.
Regulated rivers in Zambia—The case study of the Kafue river
Authors: Obrdlik P. , Mumeka A. , Kasonde J. M.
Published: February 2007

Until today, the majority of the Zambian rivers have been able to keep their natural character. Impoundment has been the principal measure carried out so far. The Kafue River is the most important waterway for the national economy. Its middle and lower sections are regulated by the Itezhi‐tezhi and Kafue Gorge Reservoirs. The changes in the natural flow pattern have threatened the ecological equilibrium of the Kafue Flats. Conductivity, concentration of sulphates and chlorides are reduced in the regulated section.
Snake river spring and summer chinook salmon: Can they be saved?
Authors: Williams John G.
Published: February 2007

Spring and summer chinook salmon Oncorhynchus tshawytscha populations from the Snake River have declined precipitously from historical levels. Declines initially were the result of overfishing, but since the late 1950s they have been primarily the result of hydroelectric dams that blocked access to spawning areas, created slack water, and caused mortalities of juvenile outmigrants. Mitigation hatcheries and juvenile collection and bypass systems at dams, transportation of juveniles from upriver dams to a release site on the lower Columbia River, a water budget, allocated spill for fish at main‐stem dams have not increased these populations appreciably. Ocean conditions may have been a factor in the low returns from 1976 through 1984, but the factors currently considered as controlling the viability of the run are the low genetic variability, lack of stress tolerance, and incidence of bacterial kidney disease inherent in the stock. With control of disease, reduced stress at main‐stem projects, and continued efforts to maintain genetic variability, the chinook salmon populations should increase and their long‐term viability should be assured.
Changes in urban stream channels in Zimbabwe
Authors: Whitlow J. R. , Gregory K. J.
Published: February 2007

Although channel change has been documented downstream of urban areas there have been few previous studies which have focused upon the spatial variation of erosion and upon examples of such channel change in tropical areas. In the Avondale stream basin, which includes part of Harare the capital of Zimbabwe the way in which the channel network has evolved from the extensive dambo system in the period 1891 to 1984 is reconstructed showing that drainage density which was initially between 0.35 and 0.80 km km−2 has increased to 3.15 km km−2 including stormwater drains. Characteristics of erosion of the modified urban channels are described and the downstream reaches indicate an average channel widening of 1.7 times involving average rates of bank erosion of 0.33 m per year. Peak discharge is estimated from channel characteristics to be increased to two times former values and it is concluded that channel type and the relationship of channel change to the accommodation of peak discharges requires further research.
Changes in the benthic invertebrate communities of the thomson river, southeastern Australia, after dam construction
Authors: Marchant R.
Published: February 2007

Benthic macroinvertebrates were quantitatively sampled at four sites, one above (T6) and three (T14A, T16, T21A) downstream of the Thomson Dam, Victoria, Australia, for three summers after completion of dam construction in 1983. Community composition was compared with that recorded previously during dam construction to determine the effects of the main environmental consequences of the dam, viz the input of fine sediment (< 2mm grain size), the temporary release of cold hypolimnetic water during summer, and altered levels of discharge. Unnaturally low summer water temperatures were only recorded at the two sites immediately downstream of the dam (in order downstream T14A and T16). After water temperatures returned to normal summer levels, species richness increased at these sites. Levels of fine sediment increased in the surface layers of the riverbed at T16 but not at T14A. By the time this study began levels at T16 had been reduced almost to pre‐dam levels. At T21A levels approximately tripled after completion of construction. At T14A and T16 marked increases in species richness occurred during this study whereas at T21A species richness did not change, and was lower than that recorded during dam construction. Ordination and classification of samples clearly displayed these changes in the benthic communities downstream of the dam and the lack of change at T6 above the dam. Altered discharge resulted in some loss of habitable area and thus total standing stock at T14A only.
Response of epiphytic diatom communities from the tailwaters of glen Canyon Dam, Arizona, to elevated water temperature
Authors: Blinn Dean W. , Truitt Robert , Pickart Anne
Published: February 2007

The composition of epiphytic diatom communities from the cold tailwaters (12°C) of Glen Canyon Dam, Arizona, was analysed after a 2 wk incubation period at 12°C, 18°C and 21°C. There was a significant change in diatom composition between 12°C and 18°C, while no significant changes occurred between 18°C and 21°C. This suggests that a temperature threshold exists between 12°C and 18°C for the diatom flora in the tailwaters of Glen Canyon Dam. At the two higher water temperatures, smaller and closely adnate taxa became more important numerically than larger, upright, cold water stenotherms. The potential importance of this compositional shift in epiphytic diatoms on macroinvertebrate grazers has management implications regarding different release programs from reservoirs.
The assessment and management of surface water quality in England and Wales
Authors: Miller D. G. , Tetlow J. A.
Published: February 2007

This paper briefly recounts the development of legislation to control water quality and discusses how the data from monitoring programmes should be used to assess water quality and direct progress towards regional and national objectives.
Fish population dynamics in the River Frome, Dorset
Authors: Mann R. H. K.
Published: February 2007

This paper examines the influence of biotic and abiotic factors on the population dynamics of salmonid and non‐salmonid (coarse) fish in a chalk river. The naturally regulated flow regime, allied to a supply of water rich in inorganic salts, gives rise to high levels of primary and secondary production. Fish growth rates are also high, but they vary with relatively small changes in the summer water temperature regime. Hence the survival of newly‐hatched fish varies and this is shown up in later years by variations in year‐class strengths.

Anadromous salmonids show a distinct seasonality in their upstream spawning migration, and many fish to not migrate until after the end of the salmon angling season. However, river discharge influences migration and in years of very low discharge the seasonal pattern can be disrupted.

Little is known concerning species interactions, or of the effect of man‐made adjustments to the river environment, on fish behaviour and distribution patterns. Information on pike predation shows that apparently common‐sense regimes of fishery management, designed to protect salmon populations, may be counterproductive.

Traditional times for cutting aquatic macrophytes as a flood alleviation measure may be detrimental to the spawning success of roach. A switch to removing the weed in the autumn would have less impact on fish populations and is more cost‐effective.

Information derived from short‐term investigations can be extremely informative, but results need to be set against a background of long‐term investigations.
The waterways bird survey of the British trust For Ornithology: An overview
Authors: Carter Steven P.
Published: February 2007

This paper describes the background and methodology of the British Trust for Ornithology's Waterways Bird Survey. The scheme aims to produce breeding population indices for a range of riparian species based on survey work carried out annually at over 100 sites throughout Britain and Ireland. Habitat data are collected at each site which allow assessments to be made of factors affecting both the numbers and distribution of particular species. The effects of habitat changes can also be investigated.

The scheme is illustrated with reference to population trends for coot (scientific names of species in the text are given in Table I) and yellow wagtail. The results of habitat studies are discussed for moorhen. This shows that densities reach a maximum on canal sites, and that on sections of the River Ouzel, Bedfordshire and Grand Union Canal, Buckinghamshire, populations were adversely affected by dredging and regrading operations.
The conservation value of water supply reservoirs
Authors: Moore David , Driver Alastair
Published: February 2007

There are over 500 water supply reservoirs in England and Wales, a total water surface of 20000 hectares, much of which has been flooded this century. Waterfowl, amphibious and aquatic wildlife have all benefited from this change, especially important after so much wetland has been drained and ploughed to increase agricultural production. Modern reservoirs include landscape and conservation in their planning, construction and operation, often leading to their notification as Sites of Special Scientific Interest soon after their construction. Examples in the Anglian Water and Thames Water regions are discussed to demonstrate their value to wildlife as well as fulfilling their prime function for water supply. Pitsford Water (Northamptonshire), Rutland Water (Leicestershire), Staines Reservoirs (Surrey), and Walthamstow Reservoirs (Greater London) show varying levels of conservation planning. Protection from recreational activity is shown to be an essential part of management at these sites.
Stream channel and habitat changes due to flow augmentation
Authors: Wolff Steven W. , Wesche Thomas A. , Hubert Wayne A.
Published: February 2007

A previously ephemeral stream is being used to convey water and create fish habitat as part of mitigation for impacts of a transbasin water diversion project. This stream, the South Fork of Middle Crow Creek, is located in the Medicine Bow National Forest, Wyoming. After two years of increased flow to the 8.8 km study reach, the amount of stream channel had increased 32 per cent and the total area of beaver ponds had more than doubled. Brook trout (Salvelinus fontinalis) stocked into the beaver ponds are surviving and growing. Factors limiting fishery development in the augmented stream include interrupted flow, discontinuous channels, and summer water temperatures exceeding 25°C. Analysis using the Physical Habitat Simulation System indicated that a flow of 0.07m3s−1 would maximize the amount of weighted usable area for brook trout under the channel conditions present in 1987.
Trichoptera and ephemeroptera as indicators of environmental changes of the Rhone river at lyons over the last twenty‐five years
Authors: Usseglio‐Polatera Philippe , Bournaud Michel
Published: February 2007

Systematic light trapping was carried out in Lyon on the banks of the Rhǒne river from 1958 to 1982, mainly in the months of June and July. The changes in the type and abundance of the adult Trichoptera and Ephemeroptera species captured over the last 25 years were studied in relation to the perturbations sustained by the river‐and thus by the larval instars.

A Correspondence Analysis carried out on the monthly samples defined a first factorial axis which could represent a ‘biological time’ scale characterized by phases of rapid (1959‐1974) or slower (1974‐1982) change of the faunal communities.

Five ‘successive’ faunal groups were defined according to the length of historical presence of each of the 88 species along this axis. The most stenoecic species (faunal groups 1, 2 and then 3) seem to disappear and gradually only a small number of species whose ecological requirements are less demanding (faunal groups 4 and 5) subsist.

This faunal impoverishment is a consequence of the increasing uniformity of the biotope caused by continuous environmental changes mainly in flow regulation. This has led to reduction in diversity of the substratum and possible food sources. Regular flush‐outs of upstream reservoirs release sediments which clog interstitial spaces over long periods and this effect has been aggravated since 1966 by the bringing into service of a dam situated just downstream from the station.

It seems that a new but delicate equilibrium has been reached since 1974; this situation probably corresponds to a less stenoecic biotic community.
Factors affecting the distribution and abundance of aquatic plants in a navigable Lowland river; the River Nene, England
Authors: Brierley S. J. , Harper D. M. , Barham P. J.
Published: February 2007

Investigations were conducted into the causes of a decline in the abundance of rooted aquatic plants in the River Nene. These were formerly troublesome to navigation and obstructed summer storm flows and were regularly cut by Anglian Water until 1976. After 1977 plant growth caused only localized problems so cutting ceased. An investigation into the causes of the plant decline was initiated in order to provide predictions for management decisions about the future use of machinery and personnel. It was concluded that there was a natural loss of plants by scouring in the abnormally high flows of 1976/7 winter. The regular pattern of maintenance dredging, which had been implemented following water industry reorganization in 1974, was shown to suppress abundance for at least five years after dredging. These two sequential events had lowered abundance over the navigable Nene to levels which no longer warrant weedcutting.
The effect of an irrigation and hydroelectric reservoir on its downstream communities
Authors: Casado C. , de Jalon D. Garcia , Delolmo C. M. , Barcelo E. , Menes F.
Published: February 2007

The Cernadilla reservoir, located on the River Tera (northwest Spain, Duero Basin) is an oligotrophic reservoir with a capacity of more than 250 × 106m3 and a depth of 70 m. The regulated flow pattern is characterized by higher summer flows, higher day flows than night ones, and lower weekend flows. The effects of this artificial flow regime on the stream ecosystem were evaluated by comparing the aquatic communities of an upstream station with those of three downstream stations, located at 1, 8, and 24 km from the dam. Physiocochemical characteristics of the water, fish and macrobenthic communities, and macrophytes were studied at each station.

Summer water temperatures were significantly lower downstream of the reservoir. Macrophyte biomass, macrobenthic diversity, and richness were reduced below the dam. The trophic structure was changed by an increase of shredders and grazers.

Fishery total biomass greatly fluctuated seasonally, but was higher above the reservoir than below it. However, in spring the trout populations were higher upstream because large numbers of spawning cyprinids from the reservoir invaded upstream reaches of the River Tera and displayed resident trout populations.
A review of the effects of water transfers in the La Grande Hydroelectric Complex (Québec, Canada)
Authors: Roy Dominique , Messier Danielle
Published: February 2007

Construction of the La Grande Complex in Eastern Canada called for complete or partial diversion of six rivers, the mean annual discharge of which varied from 60 to 1600 m3 s−1, and the transfer of water from two adjoining watersheds (1586m3 s−1) into La Grande Rivière. Three of these rivers with reduced flow, Eastmain (from 700 to 95m3 s−1), Opinaca (from 260 to 35m3 s−1), and Caniapiscau (from 1708 to 960m3 s−1) and the waterways with increased flows, Boyd‐Sakami (from 1 to 811m3 s−1) and La Grande Rivière (from 1760 to 3400m3 s−1) were intensively monitored from 1978 to 1988, while the others were surveyed sporadically. Very few modifications were observed, compared to previous conditions, in banks stability, water quality, and aquatic fauna of the affected rivers: those which appeared can be explained by the water level fluctuations, the water quality of the tributaries of the residual drainage basin, and/or by the direct influence of the reservoirs. In James Bay, the areal extent of the Eastmain River and La Grand Rivière plumes varied with discharge in an exponential relation, mostly under ice cover; resources from the coastal environment had not yet undergone any major changes. Because of the very small population dwelling in the area, less than 3000 inhabitants, modifications in the hydrological regime of these rivers did cause relatively few impacts, the main being greater banks instability in specific locations, reduction of the thickness and ice cover on La Grande Rivière, enhancement of navigation constraints on Eastmain River, and higher mercury levels in fish related to operation of the reservoirs.
The increasing damming of the Paraná basin and its effects on the lower reaches
Authors: Bonetto A. A. , Wais J. R. , Castello H. P.
Published: February 2007

The development of large impoundments along the Paraná river, particularly on the Superior section, with fifteen large dams having a capacity over 25000 MW, has had important hydrological and ecological impacts on the lower reaches. The important retention of the suspended solids by the dams has caused a significant reduction of P concentrations. With river impoundment and water eutrophication, cyanophiceae currently dominate during spring and summer, with brief but dense blooms of Anabaena spiriodes and Microcystis aeruginosa. Many fishes of the Superior Paraná have been dispersed downstream as the Itaipú reservoir covered the Guayra falls, the natural barrier for these fishes.

The most important effects of Superior Paraná dams are related to the changed hydrological regime in the alluvial Middle and Lower reaches. This floodplain plays an important role in the bioproductivity of the river. Fisheries production depends to a high degree on the relationship of the river and its alluvial valley, where the alevines and small fishes of migratory species develop after spawning. During falling river levels the waters carry large quantities of organic matter, floating vegetation, important amounts of plankton and fishes from the alluvial plain to the river. Before the dams, the river defined two subsystems which were joined for about six months during the flood season and effectively isolated during low water periods.

Since the commencement of river impoundment and flow regulation, the river ecology has begun a sequence of changes especially within the alluvial reaches.
Chinook salmon spawning surveys in deep waters of a large, regulated river
Authors: Swan George A.
Published: February 2007

In 1986 research divers surveyed and mapped deep‐water spawning redds of fall chinook salmon (Oncorhynchus tshawytscha) in selected sites within an impounded segment of the main‐stem Columbia River, Washington State, U.S.A. In velocities over 3m s−1 and depths up to 11 m, two divers riding a manoeuvrable sled made cross‐current transects communicating observations of substrate materials and deep‐water spawning sites. Surface personnel tracked the position of the sled with a laser locating system that logged the information into data storage. Subsequently, the computerized data were translated into overlaying maps depicting location of redds, substrate materials, and depth contours.

Deep‐water spawning (>3m) occurred at most survey sites in velocities between 0.6 and 0.8m s−1. The average depth of spawning was 6.5 m, and the maximum was 9.1 m‐deeper than the depth redds can normally be detected by aerial observation (3–4 m). Deep‐water spawning ranged from none to substantial in areas of near identical physical characteristics. A method for estimating abundance and density of deep‐water redds, based upon the data collected with this mapping technique, is presented. This study combined with current limited information concerning deep‐water spawning suggests that up to 80 per cent of the escapement of fall chinook salmon in this reach may spawn in deep water.
Time scales for the recovery potential of river communities after restoration: Lessons to be learned from smaller streams
Authors: Fuchs Ulrike , Statzner Bernhard
Published: February 2007

German politicians have promised that the River Rhine will be sufficiently restored within twelve years to permit salmon to live there again. Obviously the large rivers in Central Europe are more isolated from each other than smaller streams, and communities donating potential colonizers (if they exist at all) are further apart for possibly restored large rivers than for smaller streams. Thus, recovery can be expected to be faster in small streams than in big rivers after restoration (or reduction of detrimental human influence). Therefore, two restoration projects in German lowland streams, which differ in their degree of isolation, can serve as an indicator to the time periods which could at least be expected for the recovery of Central European rivers.

Under optimal conditions (almost completely intact communities upstream and downstream of a 400 m restored reach) in North Germany, sufficient recovery of benthic macroinvertebrate fauna could be achieved in relatively short periods. However, in a rather isolated stream reach in the Upper Rhine valley (closest intact lotic ecosystems of a comparable type were found 20‐25 km away) a sufficient recovery of benthic macroinvertebrate fauna was not achieved within five years after restoration, although there was high diversity of physical habitats and the water quality was acceptable (except for two oil accidents in the fourth and the fifth year).

Hence, we conclude that recovery of a large Central European river ecosystem like the Rhine, which has lost a large number of its former species and is more isolated than small streams, will require more than twelve years to reach a state significantly different from the present one.
The riparian woody plant community of regulated rivers in eastern England
Authors: Mason C. F. , Macdonald S. M.
Published: February 2007

The riparian woody vegetation (trees and shrubs) is described from a survey of fifty 1 km stretches of rivers in East Anglia, England, between 1985 and 1987. Tree loss along three rivers was estimated from 1879 maps and aerial photographs taken in 1960 and 1970. A total of 48 species of trees and shrubs were recorded, with Alnus glutinosa, Salix alba, and S. fragilis dominating the overall community. Overall tree density ranged from 0 to 185 km−1, average 73 km−1. The majority of stretches had less than 25 mature trees, with less than 10 individuals of any one species. Sites were classified, based on the frequency of occurrence of species, into four groups using TWINSPAN. Marked decreases in densities of riparian trees were apparent over the period 1879–1970, averaging 8 per cent per annum on the river with the greatest initial starting densities. Tree densities, counted from the aerial photographs of 1970, ranged from 25–35 km−1. The results from East Anglia are compared with a similar study from a less intensively managed region in western Britain.
Element transport in regulated and non‐regulated rivers in northern Sweden
Authors: Brydsten Lars , Jansson Mats , Andersson Tord , Nilsson Åke
Published: February 2007

The transport of HCO3−, SO42−, Cl−, Ca2+, Mg2+, Na+, K+, Tot‐P, MRP, Tot‐N, NO3‐N, NO2‐N, NH4‐N, Fe, Mn, silica, particulate material, and organic material (total and dissolved) were compared in three rivers regulated for the expoitation of hydroelectric power and in three unregulated rivers in northern Sweden. This evaluation was done by statistical analysis of data derived from monthly sampling near the outlets of the rivers during the period 1972–1986. Significant differences due to regulation were found for particulate matter, total‐P, Fe, and silica. Regulation decreased the transport by 10–50 per cent depending on the parameter and the river. The explanations for this effect are sedimentation of particles in impoundments and decreased erosion of the river bed due to the elimination of runoff during the snow melt period. The reduced transport of phosphorus may affect the productivity of the coastal zone of Bothnian Bay into which the rivers discharge.
A sampler for interstitial fauna in alluvial rivers
Authors: Tabacchi E.
Published: February 2007

An improved Hynes' sampler (1974) is described to study the meso‐ and microfauna inhabiting higher levels of fluvial alluvium affected by frequent water‐level fluctuations. Monthly results from a one‐year sampling survey are presented.
Fisheries ecololgy and management of the Jaraqui (Semaprochilodus Taeniurus, S. Insignis) in central Amazonia
Authors: de Brito Ribeiro Mauro Cesar Lambert , Junior Miguel Petrere
Published: February 2007

The decline of heavily exploited stocks of large, high quality, food fishes in central Amazonia has led to increasing fishing pressure on smaller taxa, especially the jaraqui (Semiprochilodus spp.). The Prochilodontids, now the most important species to the fisheries, are seined by commercial fishermen during three distinct peridos. At the beginning of the annual floods, schools of mature jaraquis in poor‐water tributaries migrate downstream to spawn in the nutrient rich white‐water rivers. During these rapid spawning runs, fishing effort is concentrated in the lowermost reaches of the tributaries. After spawning, they return in small groups to feed intensively in the flooded forest of the same tributaries from which they had migrated. This period, of approximately three months, may be considered as a natural closed season to the fisheries. The dispersal migration is most complex and requires distinct fishing strategies. In the middle of the floods large schools of fat jaraqui descend from the tributaries to the white‐water rivers again. From there, they move upstream to different poor‐water tributaries. As downstream movements are more diffcult to observe, fishermen remain at fixed fishing grounds. This contrasts with the dynamic strategies of the subsequent upstream fishing period which contributes 60 per cent of the annual catches.

Fluctuations in catch are shown to reflect year to year variations in abundance, which are linked to the hydrological cycle. Considering that fishing over the stocks of jaraqui has already more than compensated for the deficit in catch of larger species, a combination of increased effort and environmental problems could lead, in a short period to a depletion of one of the most profitable fisheries of central Amazonia. Regulation of the fisheries could benefit from a more reasonable distribution of effort among other migratory illiophagous species which remain unexploited, if the goal of sustainable yield and conservation of these stocks is to be achieved. Reserved waters in large strategic units of at least 300 km along white‐water rivers (which is equivalent to the maximum upstream displacement of jaraqui during their dispersal migrations) could also be useful to compensate for the loss of floodplain areas due to deforestaion, river regulation, use of pesticides, and mining. River impoundments in tributaries in central Amazonia may have little effect on jaraqui stocks, as spwning movements are unlikely to be directly interrupted by dams. However, alterations of the hydrological regime may also benefit from simulation of the flood cycle to mitigate potential negative impacts.
Classification of the macroinvertebrate fauna of two river systems in Southwestern Australia in relation to physical and chemical parameters
Authors: Storey A. W. , Bunn S. E. , Davies P. M. , Edward D. H.
Published: February 2007

Benthic macroinvertebrates were quantitatively sampled from thirty sites along two river systems in southwestern Australia, and patterns in community structure related to physical and chemical parameters. Classification and ordination showed a major separation between upland and lowland sites, irrespective of river system. The change in benthic community structure reflected the rapid transition in geomorphology, stream hydraulics, and water chemistry as upland forested streams exit the Darling Escarpment to give rise to open rivers, disturbed by agriculture and urban development.

One upland site was clearly influenced by a storage reservoir immediately upstream and consistently grouped with lowland sites; evidence of recovery was apparent at sites downstream. The remaining upland sites were separated on the basis of catchment; this was most likely related to stream flow permanence than any inherent catchment difference. A seasonal pattern was also detected for upland sites. Samples taken in summer or autumn were distinct from those taken in winter or spring.

In constrast, lowland sites could not be separated into distinct groups on the basis of season or drainage basin. The presence of cosmopolitan and tolerant species with a high likelihood of dispersal, together with the homogeneous nature of the sites, may account for the high degree of similarity among benthic communities of sites along the lowland rivers.

Much of the spatial and temporal variation in benthic community structure was explained by physical characteristics of the sites. Prediction of community type using chemical data alone was poor, however, this success could be improved by combining physical and chemical data, particularly for upland sites. The poor predictive success using chemical data was likely the result of the abrupt changes in the physical nature of the streams, and the absence of large spatial differences in water quality.

The successful predictive relatioship betweenm benthic community structure and physical data will enable water management authorities to detect subsequent changes in water quality in these two river systems. The predictive power of the model could be assessed in adjacent river systems for which the patterns in benthic community structure are as yet unknown.
Variability of results from the use of PHABSIM in estimating habitat area
Authors: Gan Kein , McMahon Thomas
Published: February 2007

The estimation of the area of a stream reach suitable as habitat for an aquatic species by the Instream Flow Incremental Methodology is described. An important component of the methodology is PHABSIM, which is a collection of computer programs whereby useable stream area is computed as a function of discharge. This comprises a variety of options for both hydraulic and habitat simulation. A single data set is used to calculate the useable area at one discharge for three life stages of brown trout, using various options in habitat simulation. The results are shown to vary greatly according to the particular combination of options selected, so unless calculations are founded on biologically realistic assumptions the potential within PHABSIM for the „fudging”︁ of results is considerable.
Effects of sediment and flow regime on the aquatic insects of a high mountain stream
Authors: Debrey Larry D. , Lockwood Jeffrey A.
Published: February 2007

In 1984, a broad size range of sediment (boulder to sand) was introduced into a high elevation Rocky Mountain stream in southeastern Wyoming, U.S.A. In the spring of 1986, this stream was exposed to a high discharge of 7.5 m3 s−1. From 1985 to 1987 a study was conducted to assess the impact of sediment deposition and flow regime on the aquatic insect community in context of the substrate occurrences of the insect fauna. Using a modified Surber sampler, samples were collected from June through September each year at nine stations which were rated as unimpacted, slightly‐impacted, and impacted. The addition of the sediment had minimal effect on the abundance and diversity of aquatic insects. However, high water discharge severely reduced the abundance of aquatic insects and diversity was also negatively impacted. Recovery from these impacts was very rapid. The greatest insect abundance was found in samples taken in gravel and most taxa occurred predominantly on gravel or rubble substrates.
Effect of regulation on 0+ fish recruitment in the great ouse, a lowland river
Authors: Copp Gordon H.
Published: February 2007

The recruitment of 0+ fishes in the River Great Ouse, East Anglia (U.K.), was investigated using electrofishing by Point Abundance Sampling, in order to compare the distribution and extent of fish reproduction in the river and its annexes (side channels, backwaters, etc.) with similar but unregulated lowland rivers of Europe. In all, 44 sites were sampled during three weeks in August 1989. Correspondence Analysis of the Sites‐by‐Species matrix (44 × 17) in density (fishes per m2) revealed a slight but notable longitudinal zonation of fish reproduction, unusual for lowland rivers, with the limnophils Blicca bjoerkna (L.), Scardinus erythrophthalmus (L.) and Abramis brama (L.) limited to lentic downstream sites and the rheophil Barbus barbus (L.) restricted to a few upstream sites. Thus, compared with unregulated rivers of Europe, the River Great Ouse differs by: (1) the absence of pelagic spawners, e.g. Lota lota (L.), which were historically reported as abundant; (2) the reduced range and abundance of both rheophilic and limnophilic cyprinids, e.g. B. barbus (L.), Alburnus alburnus (L.) and Blicca bjoerkna (L.), Scardinus erythrophthalmus (L.), Abramis brama (L.), Tinca tinca (L.); and (3) the predominance of generalists throughout the system, Rutilus rutilus (L.) downstream and Phoxinus phoxinus (L.) with Gasterosteus aculeatus (L.) upstream, probably to the additional detriment of the localized specialists, both limnophilic and rheophilic.
Enhancement of benthic macroinvertebrates by minimum flow from a hydroelectric dam
Authors: Weisberg Stephen B. , Janicki Anthony J. , Gerritsen Jeroen , Wilson Harold T.
Published: February 2007

The biological consequences of instituting a summer minimum flow from the Conowingo Hydroelectric Dam were investigated by comparing invertebrate abundance in the Susquehanna River during 1980, when flow shutdowns were frequent, to that in 1982, when the minimum flow (142 m3 s−1) was maintained. The minimum flow was only maintained from April 15 to September 15, and additional investigations compared invertebrate abundance before and after the minimum flow was terminated in the fall of 1982 and 1983. There was a large difference in summer invertebrate density in the between‐year comparison, with almost a 100‐fold increase in the year when the minimum flow was maintained. Most of this difference was exhibited by two taxa, chironomids and net‐spinning trichopterans. These results were consistent with findings from the fall of 1982 and 1983, when cessation of the minimum flow in September led to declines of more than three orders of magnitude in both of these taxa. The rate of decline was faster in the shoal habitat (areas dewatered at low flow, but submerged when the minimum flow is released), suggesting that dewatering was the predominant mechanism of effect. Declines were also evident in the channel habitat (always submerged), suggesting that maintenance of current velocity is also an important beneficial component of the minimum flow.