The growth of brown trout

An article discussing the factors affecting the rate of growth of brown trout, detailing the research udnertaken at Wray Castle, designed to clarify the influencing factors in different waters and investigate what would be required to increase their size. The article considers factors such as alkalinity, total hardness, the presence of coarse fish in the waterbodies and competition for food. Previous work undertaken on brown trout in Ireland by other authors is reviewed. A figure showing average growth rate of brown trout in five lakes, as determined from their scales (Lough Derg, Windermere, Loch Leven, Ullswater, Haweswater)

A Check-list of the Land Mammals of the Tanganyika territory and the Zanzibar protectorate

Volume: X

Why some fields might be rectangular: an exploration of agricultural landscapes between pre-capitalist and capitalist modes of production

This article is a preliminary investigation of possible spatial form which starts by rejecting the idea that spatial theory can be built from assumptions of isomorphism. It examines spatial form in high potential ridge valley areas which are densely populated, and identifies the transition in land configuration for pre-capitalist to capitalist modes of production. In building the argument simple geometric patterns that differentiate from the model are postulated. The basic drivers of the differing spatial systems are essentially the superstructural legal conditions which are postulated as a moving from communal, customary law to individual statutory property rights

Study of volatile contaminants in reclaimed water

Different methods were evaluated for reducing the volatile contaminants found in water recovered from urine by distillation. The use of activated carbon, addition of potassium permanganate, and the use of oxidation catalyst are described along with laboratory tests. It is concluded that catalytic decomposition appears to be feasible, and further investigation is recommended

'Paying for the Emergency by displacing the Settlers' : global coffee and rural restructuring in late colonial Kenya.

Global coffee markets entered into a deep cyclical downturn from the mid 1950s. As producers, notably Brazil and Colombia, continued to increase their output, intense struggles arose among global competitors for larger slices of a contracting market. The prospect of an economic catastrophe, following the release of Brazil's surplus stocks, preoccupied Kenya's colonial government, which was dependent on tax revenues derived from coffee sales, and was less able to support the settler-dominated industry in the face of the increased costs incurred by the Mau Mau Emergency after 1952. This left European settlers exposed, with many barely able to recover their costs of production. What began as a counter-insurgency strategy, by allowing an elite of African farmers to grow Arabica coffee (a privilege formerly reserved to settlers) was enlarged and accelerated in response to unrelenting global market pressures. These compelled the colonial government to beckon low-cost African farmers into coffee production, in a bid to save its tax base and ensure the survival of the coffee sector. Even though the Coffee Marketing Board confiscated much of their income, African farmers proved well able to rally family labour and achieve surpluses. Rationalization of production and the re-organization of the commodity chain to maintain high quality at lower cost were decisive in both reconfiguring the economic and social relationships that underpinned Kenya's independence in 1963 and securing the country's place on the world market. The aim here is to explain the crisis, and its grip on Kenya's economy during the transition to independence and beyond

Undercurrents to Independence: Plantation Struggles in Kenya’s Central Province 1959-60

The avalanche of plantation strikes which took place during early months of 1960 initiated the successive strike waves which plagued Kenya’s decolonisation process. The lifting of the Emergency and the announcement of a transition period to African majority government in January 1960 was marked by a new confidence. After years of draconian discipline, estate workers embraced trade unionism and moved into their first organised struggles over wages and conditions. They were joined by unrestricted former Mau Mau detainees and the victims of land consolidation who entered the plantation work force. The arousal of high expectation fuelled the strikes that engulfed the plantation districts of Kenya’s Central Province during the approach to independence. These events took place against a background of severe crisis within world coffee markets. Faced by this, European coffee growers attempted to compensate themselves by rationalising the plantation economy at the expense of their workers. This was met by fierce resistance from plantation labourers which was only eventually tamed as union leaders struggled to arrest the movement and surrender organisational autonomy to the state

Geostatistical models using remotely-sensed data predict savanna tsetse decline across the interface between protected and unprotected areas in Serengeti, Tanzania.

Monitoring abundance is essential for vector management, but it is often only possible in a fraction of managed areas. For vector control programs, sampling to estimate abundance is usually carried out at a local-scale (10s km2), while interventions often extend across 100s km2. Geostatistical models have been used to interpolate between points where data are available, but this still requires costly sampling across the entire area of interest. Instead, we used geostatistical models to predict local-scale spatial variation in the abundance of tsetse – vectors of human and animal African trypanosomes - beyond the spatial extent of data to which models were fitted, in Serengeti, Tanzania. 2. We sampled Glossina swynnertoni and G. pallidipes >10 km inside the Serengeti National Park (SNP) and along four transects extending into areas where humans and livestock live. We fitted geostatistical models to data >10 km inside the SNP to produce maps of abundance for the entire region, including unprotected areas. 3. Inside the SNP, the mean number of G. pallidipes caught per trap per day in dense woodland was 166 (± 24 SE), compared to 3 (± 1) in grassland. G. swynnertoni was more homogenous with respective means of 15 (± 3) and 15 (± 8). In general, models predicted a decline in abundance from protected to unprotected areas, related to anthropogenic changes to vegetation, which was confirmed during field survey. 5. Synthesis and applications. Our approach allows vector control managers to identify sites predicted to have relatively high tsetse abundance, and therefore to design and implement improved surveillance strategies. In East and Southern Africa, trypanosomiasis is associated with wilderness areas. Our study identified pockets of vegetation which could sustain tsetse populations in farming areas outside the Serengeti National Park. Our method will assist countries in identifying, monitoring and, if necessary, controlling tsetse in trypanosomiasis foci. This has specific application to tsetse, but the approach could also be developed for vectors of other pathogens. Accepted Article This article is protected by copyright. All rights reserved

Optimal-Foraging Predator Favors Commensalistic Batesian Mimicry

BACKGROUND:Mimicry, in which one prey species (the Mimic) imitates the aposematic signals of another prey (the Model) to deceive their predators, has attracted the general interest of evolutionary biologists. Predator psychology, especially how the predator learns and forgets, has recently been recognized as an important factor in a predator-prey system. This idea is supported by both theoretical and experimental evidence, but is also the source of a good deal of controversy because of its novel prediction that in a Model/Mimic relationship even a moderately unpalatable Mimic increases the risk of the Model (quasi-Batesian mimicry). METHODOLOGY/PRINCIPAL FINDINGS:We developed a psychology-based Monte Carlo model simulation of mimicry that incorporates a "Pavlovian" predator that practices an optimal foraging strategy, and examined how various ecological and psychological factors affect the relationships between a Model prey species and its Mimic. The behavior of the predator in our model is consistent with that reported by experimental studies, but our simulation's predictions differed markedly from those of previous models of mimicry because a more abundant Mimic did not increase the predation risk of the Model when alternative prey were abundant. Moreover, a quasi-Batesian relationship emerges only when no or very few alternative prey items were available. Therefore, the availability of alternative prey rather than the precise method of predator learning critically determines the relationship between Model and Mimic. Moreover, the predation risk to the Model and Mimic is determined by the absolute density of the Model rather than by its density relative to that of the Mimic. CONCLUSIONS/SIGNIFICANCE:Although these predictions are counterintuitive, they can explain various kinds of data that have been offered in support of competitive theories. Our model results suggest that to understand mimicry in nature it is important to consider the likely presence of alternative prey and the possibility that predation pressure is not constant

Variability in Avian Eggshell Colour: A Comparative Study of Museum Eggshells

Background: The exceptional diversity of coloration found in avian eggshells has long fascinated biologists and inspired a broad range of adaptive hypotheses to explain its evolution. Three main impediments to understanding the variability of eggshell appearance are: (1) the reliable quantification of the variation in eggshell colours; (2) its perception by birds themselves, and (3) its relation to avian phylogeny. Here we use an extensive museum collection to address these problems directly, and to test how diversity in eggshell coloration is distributed among different phylogenetic levels of the class Aves. Methodology and Results: Spectrophotometric data on eggshell coloration were collected from a taxonomically representative sample of 251 bird species to determine the change in reflectance across different wavelengths and the taxonomic level where the variation resides. As many hypotheses for the evolution of eggshell coloration assume that egg colours provide a communication signal for an avian receiver, we also modelled reflectance spectra of shell coloration for the avian visual system. We found that a majority of species have eggs with similar background colour (long wavelengths) but that striking differences are just as likely to occur between congeners as between members of different families. The region of greatest variability in eggshell colour among closely related species coincided with the medium-wavelength sensitive region around 500 nm. Conclusions: The majority of bird species share similar background eggshell colours, while the greatest variability among species aligns with differences along a red-brown to blue axis that most likely corresponds with variation in the presence and concentration of two tetrapyrrole pigments responsible for eggshell coloration. Additionally, our results confirm previous findings of temporal changes in museum collections, and this will be of particular concern for studies testing intraspecific hypotheses relating temporal patterns to adaptation of eggshell colour. We suggest that future studies investigating the phylogenetic association between the composition and concentration of eggshell pigments, and between the evolutionary drivers and functional impacts of eggshell colour variability will be most rewarding.Phillip Cassey, Steven J. Portugal, Golo Maurer, John G. Ewen, Rebecca L. Boulton, Mark E. Hauber and Tim M. Blackbur