Getting cosy in freshwater: Assumed to be brackish pike are not so brackish after all

Pike (Esox lucius) occupy coastal streams and rivers of the Baltic Sea, where they attain large sizes (>5 kg). These large sizes are perhaps due to the fact that they can tolerate relatively high salinities and can thus forage in the nearby more productive brackish environments. In an attempt to quantify the extent to which pike utilise brackish environments, and to provide some insight into the underlying causes for brackish water migrations, we tagged 30 pike from a western Baltic river with acoustic transmitters and were able to track 21 individuals for 1 year. Based on experienced from local anglers, this population was assumed to be brackish in nature, where individuals underwent freshwater migrations to spawn. Our findings however suggest that the smallest and most active individuals make short exits into brackish waters and do so on rare occasions. Our results further indicate that neither sex nor size is related to activity level. We suggest that these patterns reflect two distinct behaviours—active and passive—and that large pike can be supported by the food availability in the river, without the need to venture into coastal zones, thus defying the conventional view that Baltic pike are all brackish in nature.     

Spatio-temporal modelling of broad scale heterogeneity in soil moisture content: a basis for an ecologically meaningful classification of soil landscapes

We describe the classification of landscapes characterised bymineral soil using a model that calculates soil moisture availability on amonthly basis. Scotland is used as a case study area. The model uses potentialsoil moisture deficit, estimated using broad scale (40 × 40 km)climate patterns, in conjunction with meteorological station measurements toobtain finer scale values of climatic soil moisture deficit. Point estimates ofsoil available water are obtained for soil characteristics using appropriatepedotransfer functions, and geostatistical techniques are used to upscale theresults and interpolate to a 1-km grid. Known heterogeneityin soil physical characteristics is used to provide local corrections to thepotential soil moisture deficit, estimated using the climatic variables above.Temporal profiles of monthly water content are modelled for each1-km location and classified into six classes usingunsupervised cluster analysis. The spatial distribution of these classesreflects regional variations in the availability of moisture and energy, onwhich finer-grained topographic patterns are superimposed. In the case study,the broad scale spatial heterogeneity of heathlands and grasslands on mineralsoils in Scotland is shown to be strongly related to the soil moistureclassification. The results can be used in studies investigating the patternsofdistribution of communities at the landscape and regional scale.This revised version was published online in May 2005 with corrections to the Cover Date.     

A comparative and evolutionary approach to oxidative stress in fish: A review

Oxidative stress results from an imbalance between the production of reactive oxygen species and the antioxidants defences, in favour of the former. In recent years, the association between oxidative processes, environmental change and life histories has received much attention. However, most studies have focused on avian and mammalian taxonomic groups, with less attention given to fish, despite their ecological and socio‐economic relevance. Here we present a review of the extrinsic and intrinsic factors that influence oxidative processes in fish, using a comparative and evolutionary approach. We demonstrate that oxidative stress plays a key role in shaping fish's responses to environmental change as well as life history strategies. We focus on representative examples to compare and contrast how levels of oxidative stress respond to changes in temperature, salinity and oxygen availability. Furthermore, we describe how emerging threats (i.e. pollution) affect oxidative stress parameters in fish. Oxidative stress indicators are increasingly being used as biomarkers to understand the mechanisms of various human‐induced stressors, but also to understand the physiological consequences of how animals are distributed in space and time and influenced by different life stages. Despite the expansion of the field of ecological oxidative stress, we are only beginning to understand the complex ways in which oxidative stress may interact with both extrinsic and intrinsic factors in fish. We conclude with a research agenda for oxidative research on fish and note that there is need for further research particularly in the area of life history strategies and ecological implications of oxidative status, as this type of research has the potential to help us understand patterns and dynamics relevant to fish conservation.     

Risk factors associated with mastitis in dairy goats

Prevalence of intramammary infection in healthy goats was determined from 4,662 composite udder samples taken over a 9-month period. For each doe, a colostral sample and 2 milk samples were collected. Breed, age, number of days not lactating before kidding, number of lactation days, and kidding date were recorded. Coagulase-negative Staphylococcus spp were isolated from 17.5% of does, Staphylococcus aureus from 3.1%, Mycoplasma spp from 1.2%, Streptococcus spp from 0.3%, and gram-negative bacteria from 2.0%. Gram-negative organisms were associated with intermittent infections, whereas coagulase-negative staphylococci were associated with persistent infections. Intramammary infection was related to breed, number of days not lactating, and number of lactation days, as determined by log-linear analysis. Does of the Nubian breed, does with nonlactating periods of greater than 60 days, and does in the first and last third of a standard 305-day lactation appeared to be at higher risk for intramammary infection.     

Rust-resistance in some induced mutations of the new Pusa wheats 797, 798 and 799

Fully awned as well as several other radiation-mutants isolated in the wheat varieties N.P. 797, N.P. 798 and N.P. 799 were tested for resistance in the seedling stage to separate races of black and brown rust.The mutants had the resistance of the parent variety and one mutant was highly resistant to the races 10, 20 and 63 of brown rust, to which the parent strain is susceptible. There is little possibility that resistance to the additional races of brown rust in the fully awned mutant owes its origin to cross-pollination.The results of the present study suggest that by subjecting the progenies of radiated plants to a vigorous screening procedure, it may be possible to pick up also mutants possessing resistance to rusts and other diseases.

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Miss G. Birnie, a research scholar from the Netherlands working at the Botany Division, I.A.R.I., passed away on 30th June, 1960 following a brief illness. On the basis of the data left by the late Miss Birnie, this paper has been written by Dr. M. S. Swaminathan who guided this student.     

Scaling up of a mechanistic dynamic model in a GIS environment to model temperate grassland production at the regional scale

Regional‐scale ecological processes are mediated by processes occurring at local scales. Spatially explicit models are needed to understand the broad‐scale consequences of a large number of local processes, driven by factors which are heterogeneous at a broad scale. A Geographic Information System (GIS)‐based mechanistic model, which can be used as a flexible tool to investigate the regional‐scale effects of changes in environmental factors on herbage production from a Lolium perenne sward, was developed and used to investigate the consequences of aggregating driving variables at different resolutions. The model allows rigorous scaling up of previously existing field‐based modelling approaches within a GIS context. The model's mechanistic approach allows flexibility in the simulation of the separate effects of environmental driving variables and of cutting regimes. The driving variables (temperature, solar radiation, available soil moisture and soil nitrogen status) are scaled up using geostatistical techniques. The model is used to evaluate weekly changes in herbage production under environmental conditions, variable both in space and time, under different cutting regimes. It is shown that, in this model, aggregation at 1 km² is a good compromise between accuracy and practical feasibility, and that, while ignoring heterogeneity over many square kilometres can induce large errors, their magnitude and direction also depend on the model response curve to an input variable. The results obtained were consistent with the known trends in influential environmental factors. The programming within a GIS makes the model flexible in its application and, therefore, makes it easy to apply at a variety of scales.     

An assessment of the bracken problem in relation to hill farming in Scotland

Abstract. The reasons for bracken encroachment in Scottish hill land are examined. The cost effectiveness of bracken control methods are discussed and it is shown how the real cost of aerial spraying, the most practical method, has increased in the last decade. The waiving of the follow-up requirements under the DAFS grant schemes may alter this cost situation in the future. The need for more accurate estimates of the extent of the bracken problem is highlighted by the possible link between bracken and cancer in humans. Recent surveys utilizing remote sensing techniques are described and the cost of a full bracken eradication programme is estimated to be c. £80 million which is contrasted with the current level of grant assistance of c. £135 000 a⁻¹. The use of bracken as biofuel is considered as an alternative to eradication.     

A mouse lethal dose assay for detection and titration of Cowdria ruminantium (Kwanyanga strain) in goats and ticks

A mouse lethal dose assay was used to detect a mouse pathogenic strain (Kwanyanga) of Cowdria ruminantium, the etiological agent of heartwater in goats and ticks. The titer of the rickettsial organisms in goat blood was directly related to the febrile response of the goat and the rickettsia were undetectable after the fever subsided. The maximum rickettsial titer in goat blood was 10(3) mouse LD50 ml-1. Cowdria-infected goat blood was shown to retain infectivity when held on ice for up to 2 h, but when held at room temperature infectivity declined by greater than 50% in 2 h. The mouse assay detected Cowdria in feeding female Amblyomma variegatum only on the eighth day of feeding and in feeding males on the second and eleventh days of feeding. Cowdria was shown to persist in the hemolymph of the soft tick Ornithodoros coriaceus for a period of at least 2 years.