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The replacement of a native freshwater amphipod by an invader: roles for environmental degradation and intraguild predation

We assessed the extent to which an invader, Gammarus pulex (Crustacea: Amphipoda), has replaced a native, Gammarus duebeni celticus, over a 13-year period in a European river system and some of the abiotic and biotic factors that could account for this. Between 1988 and 2001, 56% of mixed-species sites had become invader-only sites, whereas no mixed sites had become native only again. The native dominated areas of higher dissolved oxygen and water quality, with the reciprocal true for the invader. Field transplant experiments revealed that native survivorship was lower in areas where it had been replaced than in areas where the invader does not yet occur. In invader-only areas, native survivorship was lower than that of the invader when kept separately and lowest when both species were kept together. We also observed predation of the native by the invader. Laboratory oxygen manipulation experiments revealed that at 30% saturation, the native's survivorship was two thirds that of the invader. We conclude that decreasing water quality favours replacement of the native by the invader.

Assessing the sensitivity and specificity of fish community indicators to management action

We assessed ten trophodynamic indicators of ecosystem status for their sensitivity and specificity to fishing management using a size-resolved multispecies fish community model. The responses of indicators to fishing depended on effort and the size selectivity (sigmoid or Gaussian) of fishing mortality. The highest specificity against sigmoid (trawl-like) size selection was seen from inverse fishing pressure and the large fish indicator, but for Gaussian size selection, the large species indicator was most specific. Biomass, mean trophic level of the community and of the catch, and fishing in balance had the lowest specificity against both size selectivities. Length-based indicators weighted by biomass, rather than abundance, were more sensitive and specific to fishing pressure. Most indicators showed a greater response to sigmoid than Gaussian size selection. Indicators were generally more sensitive at low levels of effort because of nonlinear sensitivity in trophic cascades to fishing mortality. No single indicator emerged as superior in all respects, so given available data, multiple complementary indicators are recommended for community monitoring in the ecosystem approach to fisheries management.

Understanding Risk: Contributions from the Journal of Risk and Governance

During recent years, news headlines have been rife with criticisms of the risk management practices of public and private sector entities. These criticisms have often been accompanied by calls for greater transparency in the way government entities manage risks and communicate dangers to the public. Similarly, in the private sector, the internationalisation of economic activity has heightened concerns over the potential adverse implications of mismanagement and financial scandals, and has led to calls for greater regulation and supervision. While the responses of public sector agencies and private sector actors to these challenges have differed, they share a common acknowledgement that effective governance relies on the pro-active identification, assessment, and management of risks as well as appropriate regulatory frameworks.

This edited book covers a number of divergent topics illustrating the emergence of several novel themes in the area of economic and social risks. As a communality, these novel themes relate to the complexity in which human activity in this late stage of capitalist development is embedded. This risk-generating complexity, in turn, can be observed at several levels, including workplace hazards, governance problems within the private sector or the intersection between public and private, and in relation to the economic risks faced by larger entities such as national governments.

Understanding Risk: Recent Contributions from the Journal of Risk and Governance

Following on from the format of the previous Book Understanding Risk: Contributions from the Journal of Risk and Governance, this collection of recent contributions (including work by the editor) this book is divided in three sections .  The first section examines issues relating to corporate governance in the private sector, with emphasis being placed on issues of 'Board Decision Making,' Earnings Management and Audit Committee Effectiveness'  and ' Corporate Governance Failures.'  These contributions are complemented by the second sections which looks at governance and risk issues affecting the public sector, with a focus being places on 'Public Private Partnerships' and regulation of activities in the Life Sciences.'  Section three focuses on societal risk management in relation to health, safety and the environment.  In this context, contributions are presented in relation to major debates surrounding 'Rising Trends in Cancer Cases,' dilemmas surrounding 'Medical Self Help,' 'Mental Health Policy' and the use of 'Information Technology in Health Care.'

Predatory impact of the freshwater invader Dikerogammarus villosus (Crustacea : Amphipoda)

To assess the increasing threats to aquatic ecosystems from invasive species, we need to elucidate the mechanisms of impacts of current and predicted future invaders. Dikerogammarus villosus, a Ponto-Caspian amphipod crustacean, is invading throughout Europe and predicted to invade the North American Great Lakes. European field studies show that populations of macroinvertebrates decline after D. villosus invasion. The mechanism of such impacts has not been addressed empirically; however, D. villosus is known to prey upon and replace other amphipods. Therefore, in this study, we used microcosm and mesocosm laboratory experiments, with both single and mixed prey species scenarios, to assess any predatory impact of D. villosus on a range of macro invertebrate taxa, trophic groups, and body sizes. Dikerogammarus villosus predatory behaviour included shredding of prey and infliction of