bluuebunny/crossref_metadata_2025_split huggingface dataset:
Serial discontinuities in a Rocky mountain river. I. Distribution and abundance of plecoptera
Authors: Stanford Jack A. , Ward James V. 
Published: February 2007

AbstractSamples were taken year‐round at eleven sites along the altitudinal profile (2900‐1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial‐release dams in the headwaters and middle reaches. Twenty‐two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m−2) was also greatest in this segment. Only four species (58 organisms, 48 mg m−2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m−2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m−2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m−2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river.
Changes in benthic animal production of a weir basin after eight years of succession
Authors: Fjellheim Arne , Raddum Gunnar G. , Schnell Øyvind A. 
Published: February 2007

AbstractBenthic animal production was studied in a weir basin area of western Norway in 1984, eleven years after construction of the basin and eight years after the first benthic study. Compared to estimates from 1976, a marked change in production and species composition had occurred. Benthic animal production at two stations inside the basin was 199 and 169 KJ m−2 yr−1, an increase of 440 and 270 per cent respectively compared to 1976. In a riffle upstream of the basin, the production estimate was 50 KJ m−2 yr−1, a decrease of 40 per cent since 1976. Chironomids formed the main contribution to the increased production in the weir basin, mainly through increased abundance of larger species like Stictochironomus pictulus and Micropsectra spp. Also other species more adapted to lentic water, like the ephemeropterans Siphlonurus aestivalis and Ameletus inopinatus, showed increased density. The fauna succession and increased production in the weir basin was mainly due to improved habitats and food conditions, as the amount of organic sediments had increased since the first production study.
A review of the effect of river regulation on mayflies (Ephemeroptera)
Authors: Brittain John E. , Saltveit Svein Jakob 
Published: February 2007

AbstractImpoundment 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

AbstractThe 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

AbstractData 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

AbstractDuring 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

AbstractPHABSIM, 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

AbstractTo 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

AbstractThe 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

AbstractThe 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

AbstractThis 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

AbstractUntil 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

AbstractSpring 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

AbstractAlthough 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

AbstractBenthic 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

AbstractThe 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.
Fish population dynamics in the River Frome, Dorset
Authors: Mann R. H. K. 
Published: February 2007

AbstractThis 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

AbstractThis 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.