Models of open populations with space-limited recruitment: extension of theory and application to the barnacle Chthamalus montagui.

1. Barnacles are a good model organism for the study of open populations with space-limited recruitment. These models are applicable to other species with open supply of new individuals and resource limitation. The inclusion of space in models leads to reductions in recruitment with increasing density, and thus predictions of population size and stability are possible. 2. Despite the potential generality of a demographic theory for open space-limited populations, the models currently have a narrow empirical base. In this study, a model for an open population with space-limited recruitment was extended to include size-specific survival and promotions to any size class. The assumptions of this model were tested using data from a pan-European study of the barnacle Chthamalus montagui Southward. Two models were constructed: a 6-month model and a periodic annual model. Predicted equilibria and their stabilities were compared between shores. 3. Tests of model assumptions supported the extension of the theory to include promotions to any size class. Mortality was found to be size-specific and density independent. Studied populations were open, with recruitment proportional to free space. 4. The 6-month model showed a significant interaction between time and location for equilibrium free space. This may have been due to contrasts in the timing of structuring processes (i.e. creating and filling space) between Mediterranean and Atlantic systems. Integration of the 6-month models into a periodic annual model removed the differences in equilibrium-free space between locations. 5. Model predictions show a remarkable similarity between shores at a European scale. Populations were persistent and all solutions were stable. This reflects the apparent absence of density-dependent mortality and a high adult survivorship in C. montagui. As populations are intrinsically stable, observations of fluctuations in density are directly attributable to variations in the environmental forcing of recruitment or mortality

Mental Health Social Work and the Troubles in Northern Ireland: A Study of Practitioner Experiences

• Summary: During the last decade increasing attention has been paid to the impact of the Troubles1 on social work in Northern Ireland. In this paper, the authors describe the first survey used to test some of the assumptions which exist in the literature. An 87-item questionnaire was applied to a range of social work staff currently working in, or associated with, mental health settings. One hundred and one questionnaires were returned: it is estimated that this represented over 70 per cent of mental health social workers in Northern Ireland. • Findings: The design of the questionnaire elicited both qualitative and quantitative data. The findings reveal a workforce with complex religious and national identities and many of the respondents have experienced relatively high levels of Troubles-related incidents whilst carrying out their duties in a variety of organizational and geographical settings. High proportions of respondents received minimal agency support and training to equip them to deal with Troubles-related problems faced by them during this period. • Applications: The authors conclude that the profession and employing agencies should pay greater attention to past and present effects of the Troubles on social work practice and develop appropriate strategies for supporting, training and resourcing staff in this neglected area.