bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparing the effects of pH on the sorption of metals by soil and by goethite, and on uptake by plants
Authors: BARROW N. J. , WHELAN B. R.
Published: March 2003

The effects of soil pH on sorption of cadmium, zinc, nickel and cobalt were studied by changing the pH of a soil and measuring sorption. Results were compared with published results for effects of pH on sorption of cadmium, zinc and nickel by goethite. In a further experiment, the effects of pH on the uptake of zinc and cobalt by subterranean clover were measured.

Effects of pH on sorption were described in terms of the concentration of metal ions required to produce equal sorption. Where the metal ions were incubated with the soil, unit increase in pH decreased the concentration of metal ions required about 10‐fold for zinc, about 7‐fold for nickel, about 6‐fold for cobalt, and about 4‐fold for cadmium. When the soil was mixed with a large volume of solution, the effects were similar for zinc and cadmium but slightly smaller for cobalt and slightly larger for nickel. In all cases, the magnitude of the effect varied somewhat with pH. Sorption was greater with a dilute background electroiyte than with a concentrated one and the effects of pH were greater. The effects for soil were smaller than effects of pH on sorption by iron oxides for which unit increase in pH can decrease the required concentration of Zinc 35‐fold and cadmium 11‐fold.

These results are consistent with adsorption of divalent ions on a variable charge surface that is negatively charged. They are not consistent with the adsorption of monovalent metal ions on a variable charge surface. This mechanism requires at least a 10‐fold effect of pH. They show that the change in electric potential with change in pH is smaller for reacting surfaces in soil than for goethite. The effects of changing pH on the amounts of zinc and cobalt fertilizer required for equal uptake by plants was even smaller with unit increase in pH, causing a 1.4‐fold increase in the amount of fertilizer required, that is, a 1.4‐fold decrease in fertilizer effectiveness.
A modified Kjeldahl procedure for determining strongly fixed NH4+‐N
Authors: Corti G. , Agnelli A. , Ugolini F. C.
Published: March 2003

This paper reports a procedure for determining the content of strongly fixed NH4+ in soil. The procedure consists of a Kjeldahl digestion followed by an acid attack of the residue with a 5 m HF:1 m HCl solution. Distillations after each of the two treatments recover different forms of NH4+. The procedure was tested on fine earth (< 2 mm) and skeleton (> 2 mm) fractions of two forest soils developed on sandstone parent material. In both soil fractions we evaluated three different forms of NH4+‐N: (i) Kjeldahl, (ii) non‐exchangeable and (iii) micaceous. The last is located in the interlayer of mica flakes larger than 50 μm that resist the Kjeldahl digestion and is considered strongly fixed. The total NH4+‐N content of a soil is obtained by the summation of the Kjeldahl and the micaceous NH4+‐N. In the soils under consideration, the micaceous form prevails in the skeleton because this fraction is richer in micas of sand size (> 50 μm). Following the proposed procedure, we found that micas (muscovite and biotite) contain about 3000 mg kg–1 of NH4+‐N in the interlayer. The presence of micaceous NH4+‐N in soil is generally ignored because the skeleton is usually excluded from analyses, and the micas larger than 50 μm cannot be dissolved by the Kjeldahl treatments. The micaceous NH4+ is the least extractable form of NH4+‐N, and we infer that it is the least available to plants.
Content and bioavailability of organic forms of nitrogen in the O horizon of a podzol
Authors: Johnsson L. , Berggren D. , Kårén O.
Published: March 2003

It is often thought that the most important source of nitrogen for plants and microorganisms comes from amino acids and amino sugars when they are hydrolysed in acid conditions. We did a microcosm experiment to test the hypothesis. In the experiment spruce seedlings (Picea abies L. Karst) were grown for 145 days in soil taken from a podzol Oa horizon under a long‐term nitrogen fertilization experiment (control and N‐treated soil). Net changes in different pools of organic N were determined using standard fractionation (acid hydrolysis and pyrophosphate extraction). During the experiment the amino acid and amino sugar pools decreased significantly (14% and 15% for the control and 10% and 17% for the N treatment), whereas no significant change was observed in the non‐amino acid plus non‐amino sugar fraction. On a per organic C basis there was even a significant increase in the non‐amino acid plus non‐amino sugar fraction of 11% for the control and 8% for the N treatment. Pyrophosphate extractions suggest that amino acids or amino sugars associated with the humin fraction were more accessible to microbes and plants than those associated with the humic acid, fulvic acid and hydrophilic substances. The long‐term N fertilization (about 73 kg N ha−1 was added annually as NH4NO3 during a 24‐year period) resulted in an enrichment of all major fractions of organic N, i.e. amino acids, amino sugars and non‐amino acids plus non‐amino sugars. This enrichment was largely the result of small increases in all of the amino acids rather than large increases in just a few.
The utility of Burns’s equation to describe solute movement through soil under various boundary and initial conditions
Authors: Magesan G. N. , Scotter D. R. , White R. E.
Published: March 2003

Burns’s equation for describing solute movement through soil is attractive because it is simple and predicts adequately in many instances. However, the assumptions implicit in it are not inconsistent with preferential solute flow. We have explored the consequences of this by leaching initially resident chloride and surface‐applied tritium and nitrate through 250‐mm‐long intact cores of a silt loam soil. The applied flow rates of 3 and 5 mm h−1 (realistic rainfall intensities) produced unsaturated soil conditions, except near the base where free water dripped out. Burns’s equation described the movement of the three solutes fairly successfully with the water content parameter having values between 0.29 and 0.48, similar to the actual volumetric water content of 0.47.

The leaching of resident chloride to 450‐mm‐deep mole drains in the field was also successfully simulated using Burns’s equation. However, simulation of the leaching of bromide applied to the soil surface as a solid salt was problematic. This resulted from uncertainty as to whether to treat the application as a pulse input to the flux or resident concentration. The observed behaviour fell about midway between the simulations for these contrasting initial conditions.
A 13C‐NMR study of the interactions of soil organic matter with aluminium and allophane in podzols
Authors: Parfitt R. L. , Yuan G. , Theng B. K. G.
Published: March 2003

The stabilization of organic matter in soil by interaction with aluminium (Al) or allophane is important in maintaining soil quality, and in retarding the decomposition of soil organic matter. Complexation of Al by soil organic matter may also ameliorate Al toxicity. Here we use 13C‐NMR spectroscopy to assess the interaction of soil organic matter with both Al and allophane in two poorly drained podzols containing only trace amounts of iron. The 13C‐NMR spectrum of the subsoil of the allophane‐rich One Tree Point podzol shows an intense peak at 179 p.p.m., assigned to carbon in carboxylic acids. This peak shifts to 177 p.p.m. after removal of allophane (11% of the soil mass) by treatment with HF. We infer that the carboxyl groups in the organic matter are bonded to structural Al on the surface of allophane spherules. In the non‐allophanic Te Kopuru podzol, on the other hand, the organic matter apparently interacts with Al ions in the soil solution. This soil also has more aromatic carbon and fewer carbons in carboxyl and carbohydrate structures than the allophanic sample. There is an indication that allophane stabilizes carbohydrate groups as well as carboxyl groups.
Methods for determining labile cadmium and zinc in soil
Authors: Young S. D. , Tye A. , Carstensen A. , Resende L. , Crout N.
Published: March 2003

Isotopically exchangeable cadmium and zinc (‘E values’) were measured on soils historically contaminated by sewage sludge and ones on zinc‐rich mine spoil. The E‐value assay involves determining the distribution of an added metal isotope, e.g. 109Cd, between the solid and solution phases of a soil suspension. The E values for both metals were found to be robust to changes in the position of the metal solid⇔solution equilibrium, even though the concentration of dissolved metal varied substantially with electrolyte composition and soil:solution ratio. Concentration of labile metal was also invariant over isotope equilibration times of 2–6 days. The use of a submicron filtration procedure, in addition to centrifuging at 2200 g, proved unnecessary if 0.1 m Ca electrolyte was used to suspend the soils.

The proportion of ‘fixed’ metal, in non‐labile forms, apparently increased with increasing pH, although there was considerable variation in both sets of contaminated soil. Zinc and cadmium in the sludged soils were similarly labile. Several possible methods for the measurement of chemically reactive metal were explored for comparison with E values, including single extraction with 1 m CaCl2 and a ‘pool depletion’ (PD) method. The latter involves comparing solid⇔solution metal equilibria in two electrolytes with differing degrees of (solution) complex formation, 0.1 m Ca(NO3)2 and CaCl2. Both the single extraction and the PD method gave good estimates of E value for Cd, although the single extraction was more consistent. Neither technique was a useful substitute for determining labile Zn, because of weak chloro‐complexation of Zn2+. We therefore suggest that 1 m CaCl2 extraction of Cd alone be used as an alternative to E values to avoid the inconvenience of isotopic dilution procedures.
Effect of nitrogen fertilization, cropping and irrigation on soil air composition and nitrous oxide emission in a loamy clay
Authors: Simojoki A. , Jaakkola A.
Published: March 2003

Most of the nitrous oxide (N2O) in the atmosphere, thought to be involved in global warming, is emitted from soil. Although the main factors controlling the production of N2O in soil are well known, we need more quantitative data on the interactions of soil and the environment in the soil that affect the emission. We therefore studied the effects of irrigation, cropping (fallow, barley with grass undersown) and N fertilization (unfertilized, 103 kg N ha−1) on the composition of soil air and direct N2O emission from soil (using the closed chamber method) in a factorial field experiment on a well‐structured loamy clay soil during 1 June−22 October 1993. The measurements were made weekly during the growing season and three times after harvesting. The composition of the soil air did not indicate severe anoxia in any treatment or combination of treatments, but the accumulation of N2O in the soil air indicated that hypoxia was common. At the start of the irrigation the emissions were small, even though there was much ammonium and nitrate in the soil and therefore a potential for emission of N2O produced by both nitrification and denitrification. Larger emissions occurred later. The largest emissions were found when 60–90% of the soil pore space was filled with water. Irrigation and fertilization with N both roughly doubled the cumulative N2O emission. Growing a crop decreased it by a factor of 3–7. Most N2O was lost from the irrigated fertilized soil under fallow (3.5 kg N ha−1), and least from the unirrigated unfertilized soil under barley (0.1 kg N ha−1).
Evaluation of a nitrogen transport and transformation model in a bare soil
Authors: Garnier P. , Néel C. , Mary B. , Lafolie F.
Published: March 2003

Simulation models are useful tools to understand the interaction between the transformation and the transport of nitrogen in the field. This study was done to calibrate, test and analyse a mechanistic, one‐dimensional model that describes the transport and transformations of nitrogen in the soil. The physical module describes transport of water, heat and solute, and the biological module simulates transformations of C and N with a restricted number of measurable organic pools. The calibration was based mainly on laboratory experiments independent of those used to evaluate the model. The evaluation procedure used field data collected on a bare loamy soil. The profiles of water content, water potential, temperature, chloride and nitrate (15N‐labelled and unlabelled) concentrations were measured from 0 to 150 cm continuously for 1 year. Simulated results were in good agreement with experimental data. However, some discrepancies were noticeable for chloride and nitrate concentrations in the deep layers. These differences were probably due to an underestimation of mass transport in the deep layers. A sensitivity analysis was carried out to determine the response to changes in some parameters in terms of mineralization, leaching and model efficiency. Mineralization is more sensitive to biological factors whereas nitrate leaching is more sensitive to initial and boundary conditions and hydraulic parameters. The experiment ran for only 1 year, which was too short a time to test biological factors.
Simulating the dynamics of glucose and NH4+ in alkaline saline soils of the former Lake Texcoco with the Detran model
Authors: Luna‐Guido M. L. , Dendooven L.
Published: March 2003

The turnover of organic matter determines the availability of plant nutrients in unfertilized soils, and this applies particularly to the alkaline saline soil of the former Lake Texcoco in Mexico. We investigated the effects of alkalinity and salinity on dynamics of organic material and inorganic N added to the soil. Glucose labelled with 14C was added to soil of the former Lake Texcoco drained for different lengths of time, and dynamics of 14C, C and N were investigated with the Detran model. Soil was sampled from an undrained plot and from three drained for 1, 5 and 8 years, amended with 1000 mg 14C‐labelled glucose kg−1 and 200 mg NH4+‐N kg−1, and incubated aerobically. Production of 14CO2 and CO2, dynamics of NH4+, NO2– and NO3–, and microbial biomass 14C, C and N were monitored and simulated with the Detran model. A third stable microbial biomass fraction had to be introduced in the model to simulate the dynamics of glucose, because > 90 mg 14C kg−1 soil persisted in the soil microbial biomass after 97 days. The observed priming effect was mostly due to an increased decay of soil organic matter, but an increased turnover of the microbial biomass C contributed somewhat to the phenomenon. The dynamics of NH4+ and NO3– in the NH4+‐amended soil could not be simulated unless an immobilization of NH4+ into the microbial biomass occurred in the first day of the incubation without an immediate incorporation of it into microbial organic material. The dynamics of C and a priming effect could be simulated satisfactorily, but the model had to be adjusted to simulate the dynamics of N when NH4+ was added to alkaline saline soils.
The design of porous material sensors to measure the matric potential of water in soil
Authors: Whalley W. R. , Watts C. W. , Hilhorst M. A. , Bird N. R. A. , Balendonck J. , Longstaff D. J.
Published: March 2003

In recent years the use of porous material sensors for matric potential, which were originally intended for soil drier than −100 kPa, has been extended to wet soils. In these wetter soils, unpredictable behaviour of the sensors has been reported. We have studied the design of porous material sensors of matric potential in soil and propose a hypothesis to explain this unpredictability, and suggest recommendations for a design of sensor which will behave more reliably. The development of an experimental porous material sensor of matric potential based on this design is described. It operates between 0 and −60 kPa, and both the drying and wetting moisture characteristics were measured. In this sensor the porous material was a ceramic and its water content was measured with a dielectric water content sensor. We tested a simple closed‐form hysteresis model to convert the measured water content of the porous material into matric potential under laboratory conditions. This was shown to give better results than using a calibration based on the drying moisture characteristic curve, where the predicted matric potentials were too small. The use of the experimental sensors in the field environment is described. Both types of sensor were installed using the same procedure. As far as we are aware the experimental sensor described in this paper is the first porous material sensor of matric potential that can be installed in the same way as a conventional tensiometer. Both conventional tensiometers and the experimental porous material sensors gave similar estimates of matric potential.
Fate of anthracene in contaminated soil: transport and biochemical transformation under unsaturated flow conditions
Authors: Weigand H. , Totsche K. U. , Kögel‐Knabner I. , Annweiler E. , Richnow H. H. , Michaelis W.
Published: March 2003

To obtain reliable estimates for the loss of polycyclic aromatic hydrocarbons (PAHs) from contaminated soils, one has to distinguish between (i) losses due to release and solute transport and (ii) losses resulting from degradation. We studied the interplay of these processes in a column experiment representing a typical soil contamination scenario: in the upper part of the column was a contaminated layer, spiked with 9‐13C‐labelled anthracene, and beneath it uncontaminated pristine soil. The experimental course comprised a steady‐state flow phase (constant irrigation for 4 months) followed by several periods during which flow was halted. The effects of varied residence time on anthracene biodegradation and on anthracene mass transfer were investigated. We monitored labelled anthracene and its transformation products, dissolved organic carbon, electric conductivity (EC), pH, and inorganic carbonate content in the column effluent, and the CO2 evolved.

Under steady‐state flow, pH, dissolved organic C, and EC approached steady states after 350 pore volumes. Concentrations of anthracene in the effluent, however, increased continuously and levelled off after 800 pore volumes. This marked retardation reflects the great affinity of anthracene to soil organic matter. The response to interruptions in the flow revealed that mass is transferred without equilibrium between solid and liquid phase for both anthracene and dissolved organic C. Thus, residence time is one factor controlling the concentration of anthracene in the effluent and therefore the export of contaminant to the aquifer. In the course of the experiment several labelled anthracene degradation products appeared in the effluent. At least three of them were identified as transformation products showing a dramatic increase in mobility relative to the parent compound. A third of the overall anthracene loss from the column was due to solute transport, and biodegradation was responsible for the remaining two thirds. The incomplete degradation of anthracene leads to the formation of highly mobile transformation products and thus promotes the export of carbon, derived from the contaminant.
Physicochemical factors controlling the release of dissolved organic carbon from columns of forest subsoils
Authors: Münch J.‐M. , Totsche K. U. , Kaiser K.
Published: March 2003

Retention of dissolved organic carbon in soil depends on the chemical and physical environment. We studied the release of organic carbon from three carbonate‐free forest subsoil materials (Bs1, Bs2, Bg) in unsaturated column experiments as influenced by (i) variations of the flow regime and (ii) varied chemical properties of the irrigation solution. We investigated the effect of flow initiation, constant irrigation, interruptions to flow, and variation in the effective pore water velocity on the release of organic C. The influence of ionic strength and cation valence in the irrigation solution was studied by stepped pulses of NaCl and CaCl2. The release of C from all materials was characterized by an initial large output and a decline to constant concentrations under long‐term irrigation. Interrupting the flow increased its release when flow was resumed. The release from the Bs1 material was not related to the duration of the interruption. The Bs2 material, in contrast, released organic carbon in a way that was successfully described by a kinetic first‐order model. Increased pore water velocity decreased the concentrations of C in the effluent from it. The pH of the irrigation solution had negligible effects on the mobilization of C. Increased ionic strength reduced the release, whereas rinsing with distilled water increased the concentrations of C in the effluent. The response of dissolved C to pulses of weak solutions, however, was sensitive to the type of cation in the previous step with strong solutions. The results suggest that the release of organic matter in the soils depends on its colloidal properties.
Distribution and fractionation of heavy metals in pairs of arable and afforested soils in Denmark
Authors: Andersen M. K. , Raulund Rasmussen K. , Hansen H. C.B. , Strobel B. W.
Published: March 2003

Afforestation of sandy arable soils in northern Europe is likely to lead to an increase in the soil's acidity and changes in the behaviour of the organic matter, and this might affect the ability of the soil to retain heavy metals. It is important to assess the impact of such a change in the land use on the solubility of the heavy metals and to assess the risk of leaching to surface‐ and groundwater and the possible entrapment of heavy metals in the tree canopy. The impact of afforestation was assessed by excavating soil profiles in adjacent 34‐year‐old Norway spruce stands and arable plots at four different sites. We found that after 34 years the pH had decreased and cations were depleted in the topsoil under forest. The aqua regia‐extractable heavy metals were determined, and the heavy metal binding within the soil was assessed using a modified version of the BCR (Community Bureau of Reference) sequential extraction procedure. Higher contents of heavy metal were found in the arable plots in the loamy sand soils. Cadmium was found only in the most mobile fractions. The content of Pb in the subsoil was strongly correlated with the clay content, but not in the topsoil, which suggested that Pb had been added to the topsoil. We found strong correlations between the clay content and the Cu, Ni and Zn in the residual fraction, leading us to conclude that much of the Cu, Ni and Zn is of geological origin. No significant differences in the heavy metal fractionation between forest and arable soil were found, presumably because 34 years of different land use is not long enough to produce such differences.
Microaggregates in agricultural soils and their size distribution determined by X‐ray attenuation
Authors: Leifeld J. , Kögel‐Knabner I.
Published: March 2003

Understanding mechanisms of microaggregate formation in soils requires knowledge of their exact size distribution. With this in mind, we have used X‐ray attenuation to determine the size distributions of microaggregates and primary particles in the range 0.2–63 μm, with a resolution of 100 size increments. Ten arable and grassland soils with organic C contents ranging from 14.7 to 37.7 g kg−1 were analysed. They were subjected to ultrasound at 52 J ml−1 which destroyed most aggregates > 63 μm to give microaggregates in the size range 1–63 μm. The size distribution of microaggregates differed significantly from that of primary particles and was largely independent of their organic C content. Microaggregates were most abundant in 19 of the 100 size increments, contributing to 92% of the major peaks of the size distribution. These preferred increments differed from those of primary particles, but the order for the two was similar. Further analysis of the size distribution revealed a larger mean weight diameter of microaggregates, depending on the size distribution of primary particles. The results suggest a major effect of the size distribution of primary particles on microaggregation, whereas land use seems to have a negligible effect. The proportion of mechanically dispersible clay decreased with increasing C content and indicates structural stability at the microscale.
Introduction and dispersion of the bullhead, Cottus gobio L., in a sub‐Arctic salmon river in northern Finland
Authors: PIHLAJA  , NIEMELÄ  , ERKINARO
Published: March 2003

The bullhead, Cottus gobio L., was observed in the River Utsjoki in the far north of Finland for the first time in 1979. This river is a tributary of the sub‐Arctic River Teno, which flows into the Arctic Ocean and is one of the most important salmon rivers in northern Europe. The bullhead does not belong to the natural fish fauna of the Finnish river systems flowing into the Arctic. It was probably introduced by anglers as bait or accidentally during the water exchange activities as salmon fry were transferred from Finnish hatcheries to northern Norway. A viable bullhead population has dispersed through the River Utsjoki catchment. In 1995 its range extended from the lowest part of the river to a point 43 km upstream. It is highly probable that it has also entered the mainstem of the River Teno.
Downstream fish migration from two regulated lakes monitored by hydroacoustics
Authors: VEHANEN  , HYVÄRINEN  , MÄKI‐PETÄYS
Published: March 2003

The migration of fish from two large northern Finnish lakes to their outflowing rivers was studied by echosounding and exploratory fishing. Both lakes are regulated for hydroelectric purposes. In both rivers, two sonar stations with stationary up‐ and down‐looking transducers were used to collect data for one year. The fish migration rate in the River Oulujoki was greater than in the River Paatsjoki. In the River Oulujoki, the fish migrated mainly downstream and in the River Paatsjoki both down‐ and upstream. In the River Paatsjoki, larger fish showed active migration in the spring and autumn, whereas in the River Oulujoki the increase in the migration occurred simultaneously in all size groups. The different species composition and the different nature of the lakes, together with the different regulation practices, were considered to be responsible for the varying migration patterns. It was concluded that no barriers to fish migration should be built on these rivers.
Comparing river basins world‐wide and contrasting inland fisheries in Africa and Central Amazonia
Authors: PETRERE  , WELCOMME  , PAYNE
Published: March 2003

An analysis of covariance relating basin area (A, km2) to river length (L, km) and discharge rate (D, m3 s–1) was performed for two continents and showed that the two covariates (L and D) were highly significant and that the strength of the relationship changed between continents. For comparison, D was excluded but the result remained the same. Although geomorphological models are useful for establishing global levels of production, these regressions should be applied with caution. Historically, simple statistical models were developed to predict fish catches in rivers. These, based upon regression of catches on channel length or basin area for Africa and Central Amazonia, are contrasted in this paper because of their generally similar approach.
Present state and perspectives for the southern Brazil shelf demersal fisheries
Authors: HAIMOVICI M.
Published: March 2003

The demersal fish stocks in southern Brazil were assessed from landings and catchper‐unit effort data trends between 1975 and 1994, available information on the life history patterns, and population dynamics of the most important species. The fishing gears, mostly otter and pair bottom trawls in the 1970s, diversified towards double‐rig trawls for fish and shrimp and bottom gill nets in the mid 1980s, and bottom longlines in the upper slope in the early 1990s. There were also some less successful attempts with traps for fish and crabs. The demersal fisheries are more intensive in winter when migratory species move northward, associated with the seasonal displacement of the western boundary of the Subtropical Convergence. Landings between 1975 and 1994 were mostly of sciaenid fishes (>70%) and elasmobranchs (10%) and oscillated around 59 000 t. There was not a decrease in total landings but a shift from more to less exploited stocks. Since 1989, 4% of the landings came from depleted stocks of Pagrus pagrus (L.), Netuma barba (Lacépède), Pogonias cromis (L.) and Rhinobatos horkelli (Muller & Henle); 37% from overexploited stocks: Micropogonias furnieri (Desmarest), Paralichthys patagonicus Jordan, Squatina guggenheim Marini, and Galeorhinus galeus (L.); 24% from heavily exploited stocks of Umbrina canosai Berg, and Macrodon ancylodon (Bloch & Schneider); and 35% of Cynoscion guatucupa (Cuvier) and small stocks with unclear status. The demersal fisheries are virtually unmanaged and future landings are expected to decrease if fishing pressure remains high. Effective management will require the participation of all three countries in the region because most of the stocks fished in southern Brazil are shared with Uruguay and Argentina.
Effect of habitat type on growth and diet of brown trout, Salmo trutta L., in stream enclosures
Authors: GREENBERG L. A. , DAHL J.
Published: March 2003

The effect of habitat on the growth and diet of brown trout, Salmo trutta L., stocked at the same densities in nine stream enclosures, comprising three habitat types of different quality, were tested. The habitats, which were created based on microhabitat preference data, were a shallow water habitat lacking cobbles (habitat 1), a deeper, mixed cobble‐bottomed (128‐384 mm diameter) habitat (habitat 2) and a large cobble‐bottomed (256‐384 mm) habitat of intermediate depth (habitat 3). Brown trout were found to have greater increases in total biomass in habitats 2 and 3 than in habitat 1. The pattern for length did not follow that of biomass as trout had greater increases in total length in habitat 2 than in the other two habitats. Biomass of food in trout diets reflected habitat‐specific fish biomass changes, with a greater total biomass of prey as well a greater biomass of the leech, Erpobdella, in habitats 2 and 3 than in habitat 1. There were no habitat‐specific differences in the biomass of benthic or drifting invertebrates in the enclosures, with the exception of a tendency for an effect of habitat on the biomass of Erpobdella. Although there may have been habitat‐specific differences in food resources that were not detected, it is believed that the higher biomass growth in habitats 2 and 3 may have reflected differences in cover afforded by the deeper water and coarser substrates and/or improved foraging opportunities facilitated by the larger volumes of water in the deeper habitats in which the trout could search for prey.
A review of a model for qualitative evaluation of exploitation levels in multi‐species fisheries
Authors: Welcomme R. L.
Published: March 2003

The fauna of inland waters, especially in the tropics, consist of complex assemblages of numerous species, which are not accessible to analysis by conventional stock assessment methods. The formulation of policies for management and conservation requires alternative models which are capable of predicting the ways in which such assemblages change in response to fishing or other stresses. Historically, models which group species according to simple parameters have proved adequate to provide the level of advice needed to indicate ecosystem health and sustainability of yield from the fishery. Such models have received relatively little attention, and can be profitably further developed and refined. The present review concludes that, out of the various explanatory variables, the mean length of fish caught is one of the most significant together with the numbers of species in the catch and the time taken for catches in fluctuating systems to respond to floods. More complex indicators are based on emergent characteristics of the system such as the production:biomass or predator:prey ratios. Three major strategies are identified for management based on responses of fish assemblages to increases in effort.
Competitive exclusion of brown trout Salmo trutta L., by rainbow trout Oncorhynchus mykiss Walbaum, in lake tributaries, New Zealand
Authors: Scott D. , Irvine J. R.
Published: March 2003

Spawning runs of brown trout Salmo trutta L., and rainbow trout, Oncorhynchus mykiss Walbaum, were compared in three tributaries of two lakes for timing, numbers and redd characteristics. Redd characteristics for the two species in four other streams were examined. No significant differences in redd characteristics between the two species were observed, but in all lake tributaries the possibilities of superimposition of spring spawning rainbow trout on redds of brown trout were examined. A common feature was the high ratio of numbers of spawners to the area of preferred spawning gravel, and it was concluded that in the lake tributaries, superimposition resulted in increased mortality of brown trout eggs, and in one case elimination of the brown trout population. Management possibilities for control of the species proportions in comparable situations are discussed.
Efficiency of oxbow lake management systems in Bangladesh to introduce cage culture for resource‐poor fisheries
Authors: Chowdhury M. A. Kabir , Yakupitiyage A.
Published: March 2003

A total of 5488 ha of oxbow lakes in Bangladesh has recently gained importance as a potential fishery resource. The growing need to utilize this resource to a fuller potential requires consideration of cage culture by resource‐poor fishing communities as a compliment to existing stock enhancement programmes. In the present study, the existing management systems of eight lakes are reviewed. Water quality was analysed with reference to the largest lake, i.e. Lake Baluhar. During the present study, > 100 cm transparency indicated the suitability of a lake for cage culture. Other water quality parameters, especially dissolved oxygen, ammonia and nitrite concentrations, also indicated suitability for cage culture. Non‐fisheries activities, such as the use of agricultural pesticides in the lake catchment and jute retting in its basin, were identified as the most harmful to fish by the majority of the fishermen. An integrated pest management programme using rice–fish based rearing systems in the lake catchment is recommended. It is further recommended that a unified management system should replace the existing dispersed systems under different management bodies.
Development and use of surface waters, and the fate of the related fisheries in the Berlin area of Germany
Authors: Grosch U. , Rennert B. , Hilge V.
Published: March 2003

Berlin, Germany, has a population of some 3.5 million inhabitants and covers an area of 889 km2, of which 58 km2 (6.4%) consist of various sizes of rivers and lakes. The landscape is characterized by glacial deposits, slow‐flowing lowland rivers and shallow lakes with a maximum depth of 16 m. There are some 60 lakes which are < 1 ha and more than 500 natural pond‐like waters. The primary fishing waters are the Rivers Spree, Dahme and Havel, the latter being a lacustrine body of water. Today there are 13 full‐time and 17 part‐time fishery enterprises, and 40 000–50 000 recreational fishermen. The main fish species of commercial interest are European eel, Anguilla anguilla (L.), pike perch, Stizostedion lucioperca (L.), perch, Perca fluviatilis L., pike, Esox lucius L., and tench, Tinca tinca (L.). In recent years, the total catch from the commercial fishery has consisted of ≈ 100 t of high valued fish and another 300 t of less‐valued species, such as bream, Abramis brama (L.), roach, Rutilus rutilus (L.), and silver bream, Blicca bjoerkna (L.) Over the past 10 years, human activities, including the use of water for industrial purposes, navigation on waterways and recreation, have changed the water bodies and their fish stocks, and reduced the economic value of the fishery. Discharges by the chemical industry located in the city caused severe problems in the 1980s, when the contamination of fish by dichlorodiphenyltrichloroethane, HCH, lindane and polychlorinated biphenyls led to a ban on the marketing of the catch until 1993. Heavy eutrophication originating from upstream agriculture and effluents from sewage plants presents another problem. Measures taken for more than 40 years under two different political systems are described. These were implemented to control the stocks of coarse fish until better water quality was achieved. The measures also helped to sustain the fishery enterprises.
Water outflow as a cause of changes in trophic conditions for zooplanktivorous fish in reservoirs
Authors: Pehlivanov L.
Published: March 2003

The seasonal changes and vertical distribution of zooplankton, the export of zooplankters by outflow through water management installations, and the feeding of zooplanktivorous fish were studied in two Bulgarian reservoirs. In a bottom‐draining reservoir, planktonic crustacea > 1.0 mm were found to be selectively exported as a result of their diurnal vertical migrations. Increases in water outflow for irrigation resulted in a decrease in total zooplankton abundance, as well as changes in zooplankton size and species composition at the beginning of the summer. At the same time, major changes occurred in the feeding patterns of bleak, Alburnus alburnus (L.), and juvenile pikeperch, Stizostedion lucioperca (L.), the principal zooplanktivores in this reservoir. It is easy for bleak to switch to feeding on an alternative food, but a lack of available large prey organisms is suggested as the main cause of the downstream movement of pikeperch juveniles. In a surface‐draining reservoir, the pattern of zooplankton export corresponded to those in natural lakes. Discharged water carried with it mainly small‐sized epilimnetic zooplankton from the most numerous groups (i.e. rotifers, juvenile copepods and cladocerans) in the reservoir. Furthermore, outflow exports represent a relatively small part of total zooplankton number, and thus, do not disturb the natural zooplankton succession, and changes in abundance and composition Coincidental changes in the trophic responses for zooplanktivores (mainly juvenile cyprinids and percids) were not found.
Prespawning migratory behaviour and spawning success of sea‐ranched Atlantic salmon, Salmo salar L., in the River Gudenaa, Denmark
Authors: Aarestrup K. , Jepsen N. , Rasmussen G. , Økland F. , Thorstad E. B. , Holdensgaard G.
Published: March 2003

The migratory behaviour of sea‐ranched Atlantic salmon, Salmo salar L., was analysed by radio‐telemetry in the River Gudenaa, Denmark. The main objectives were to: (1) estimate mortality of returning adults through the fjord; (2) observe rate of progression and migratory pattern in the fjord and river; and (3) record whether spawning occurs in the river. Forty‐two returning salmon (19 males and 23 females of total body length from 60–97 cm) reared and released as smolts, were caught and equipped with external radio transmitters in the outer estuary of the River Gudenaa in 1994 and 1995. Of the tagged salmon, 18 (43%) were caught in the estuary, four (10%) were not recorded after release and 20 (47%) entered the river. The mean rate of progression through the fjord was 7.6 km d−1 (range 1.4–18.2) in 1994 and 5.4 km  d−1 (range 1.6–17.1) in 1995. Eleven salmon were alive at the onset of the spawning period. Eight were retrieved dead from the river during or after the spawning period; four with empty gonads assumed to be successful spawners, and four with intact gonads. In 1994, unsuccessful spawners (found dead with intact gonads) entered the river earlier and had a longer total migration distance in the river compared to successful spawners. This suggests that spawning success of sea‐ranched salmon is associated with time of river entry and river migration length.
Comparing size‐limit strategies for exploitation of a self‐thinned stream fish population
Authors: Nordwall F. , Lundberg P. , Eriksson T.
Published: March 2003

There is increasing evidence that territorial stream fish populations exhibit some degree of self‐thinning. Four size‐limit strategies were examined, under which a size‐structured model population exhibiting self‐thinning was exploited. The effects of: (1) increased minimum‐size limits; (2) protection of spawners; (3) decreasing maximum‐size limits; and (4) slot limits (prescribe lower and upper size limits of fish that must be released) were analysed in terms of population size and mean body size in the population after harvest. Biomass and numbers harvested, mean size of fish taken and proportions of different sizes in the population after harvesting were also analysed. Combinations of high exploitation rates and high minimum‐size limits maximized both the number and biomass harvested while it favoured post‐harvest abundance and the proportion of larger sizes in the population. When harvest rates and minimum‐sizes were increased, the combinations of these that maintained or increased yield were successively narrowed. Protection of spawners and slot limits did not come close to reaching the levels of post‐harvest abundance, yield, positive size structure and endpoints of harvest rates that were obtained with a high minimum size applied to the fishery. Maximum‐size limits favoured the abundance of smaller size‐classes. The results emphasize the advantages of setting the largest sizes of fish in the population as a minimum size that can legally be retained.
Use of geographical information systems as a tool for predicting fish yield in tropical reservoirs: case study on Sri Lankan reservoirs
Authors: De Silva S. S. , Amarasinghe U. S. , Nissanka C. , Wijesooriya W. A. D. D. , Fernando M. J. J.
Published: March 2003

Use of geographical information systems (GIS) in inland fisheries has hitherto been essentially restricted to site evaluation for aquaculture development and assessment of limnological changes in time and space in individual water bodies. The present GIS study was conducted on the land‐use pattern of the catchments of nine reservoirs in Sri Lanka, for which detailed fishery data, viz. yield, fishing intensity, landing size of major constituent species, together with selected limnological data such as conductivity and chlorophyll‐a, were available. Potential statistical relationships (linear, curvilinear, exponential and second‐order polynomial) of fish yield (FY, in kg ha−1 yr−1) to different land‐use patterns, such as forest cover (FC, in km2) and shrub‐land (SL, in km2), either singly, or in combination, and/or the ratio of each land type to reservoir area (RA in km2) and reservoir capacity (RC in km3), were explored. Highly significant relationships were evident between FY to the ratio of SL and/or FC+SL to RA and/or RC. Similarly, the above land‐use types to RA and RC ratios were significantly related to limnological features of the reservoirs. The relationships of FY to various parameters obtained in this study were much better correlated than those relationships of FY to limnological and biological parameters used in yield prediction in tropical and temperate lacustrine waters previously.
The effect of a closed area and beach seine exclusion on coral reef fish catches
Authors: McClanahan T. R. , Mangi S.
Published: March 2003

Fish landing data from the Mombasa Marine National Park (MNP) and a marine reserve exploited by various gears were studied over a 5‐yr period to determine the influence of the closed area and different gears in fisheries. The number fishing and boats per landing site was constant, but total and catch per unit effort progressively declined in all sites on an annual basis irrespective of the existence of a marine reserve, exclusion of the beach seines or use of gear. Differences between landing sites were most pronounced when analysed on a catch per area as opposed to the more standard catch per fisherman, suggesting compensation in human effort when catches decline. A marine reserve next to a closed area that excluded beach seines had the highest catch per area (5.5 kg ha−1 month−1) despite having the highest density of fishermen (0.07 ± 0.02 fishermen ha−1 month−1). The annual rate of decline in the catch was lower than the other sites at around 250 g day−1compared with 310–400 g day−1in the other sites. One landing site, which excluded beach seine landings for more than 20 yrs, had a high catch per area (∼5.3 kg ha−1 month−1), but after experiencing a doubling in the effort of other gears (line, speargun and trap), the catch per fisherman and area were reduced. Environmental or habitat degradation and excessive effort remain the most likely explanation for the overall declines in catch from 1995 to 1999. Closed areas and beach seine exclusion have the potential to increase catch rates, but the first often reduces the total fishing area and possibly leads to a loss of total catch, at least on a time scale of less than 10 yrs. The exclusion of beach seines can lead to an increase in other gear types that can also cause reductions in catch.
Thermal regime in the hyporheic zone of two contrasting salmonid spawning streams: ecological and hydrological implications
Authors: MALCOLM I. A. , SOULSBY C. , YOUNGSON A. F.
Published: March 2003

The temperatures of stream water and hyporheic water were monitored in spawning areas of an upland stream (Girnock Burn) and a degraded lowland stream (Newmills Burn). Both streams are located in North‐east Scotland and are spawning streams for Atlantic salmon, Salmo salar L., and brown trout, S. trutta L. Monitoring between the spawning and hatching of ova revealed significant differences in the thermal regimes of the two sites. Whilst temperatures in stream and hyporheic water were similar in the Girnock, notable attenuation in the Newmills Burn resulted in increasing moderation of thermal regime with hyporheic depth. This probably reflects contrasting groundwater–surface water interactions in the two systems. In the Girnock an open gravel stream bed and lack of groundwater influence resulted in stream water downwelling through the gravel. In contrast, fine bed sediments and local groundwater inputs resulted in more complex stratification of temperatures in Newmills Burn. However, even in the conditions of the Newmills Burn, temperature based salmonid embryo development models predicted that egg burial depth has an insubstantial effect on ova development.
Atlantic salmon, Salmo salar L., and sea trout, Salmo trutta L., passage in a regulated northern river – fishway efficiency, fish entrance and environmental factors
Authors: LAINE A. , JOKIVIRTA T. , KATOPODIS C.
Published: March 2003

The number and the size of Atlantic salmon, Salmo salar L., using the Isohaara fishway was elevated by increasing the fishway discharge and by changing the type of the pass entrance. The fishway is intended to help fish bypass a hydroelectric station located close to the mouth of the large, regulated River Kemijoki, in northern Finland. Multi‐sea‐winter (MSW) salmon returned to the river mouth during peak flows in early June but did not use the fishway until 1 month later. Their number in the fishway was positively correlated with the tailwater level. One‐sea winter (1‐SW) salmon, which arrived approximately one month later, started to enter the fishway without corresponding delays. In autumn, a high tailwater level and a small drop at the fish entrance seemed to be needed for the successful passage of these small‐sized salmon and sea trout, Salmo trutta L.