On the stock–recruitment relationships in fish population models

The framework of this article is modeling applied to fisheries. It aims at relating some classical stock–recruitment curves to a dynamic structured model, consisting of the adults stages of the stock and a pre-recruits stage (i.e., eggs, larvae, juveniles). The main result is that no functional stock–recruitment relationship can be found, unless further restrictive assumptions are added to the model (slow–fast dynamics and uniformity). Among the curves thus obtained is the Beverton–Holt curve, but not Ricker's.     

Recent Recovery of Lake Water Quality in Southern Québec Following Reductions in Sulfur Emissions

Since 1985, monitoring activities have been conducted in a networkof 43 lakes comprising the Québec portion of the Long-Range Transport of Airborne Pollutants (LRTAP) program. The results to date indicate that Québec lakes generally are responding positively to the generalized decline in precipitation sulfate (SO₄ ^2-), with 40 of the 43 lakes now showing steep declines in SO₄ ^2- concentrations. The drop in SO₄ ^2- was associated with a significant decrease in Ca²⁺ concentrations in 77% of the lakes (67% for Mg²⁺ concentrations). Overall, the acid-neutralizing capacity was increasing in 19 lakes and decreasing only in three, while 21 lakes showed no temporal trends. Compared with previous trend studies of the LRTAP-Québec network for the period of 1985–1993, the longer period (1985–1999) shows a clear improvement, with the proportion of lakes that were acidifying changing from 24 to 7% and with the proportion of lakes that were recovering changing from 16 to 35%. These observations suggest that the recent drop in SO₄ ^2- deposition in the northeastern U.S. and eastern Canada was significant enough to allow chemical recovery for a significant proportion of Québec lakes.     

Assessment of contamination and biomarker responses in two species of herons on the St. Lawrence river

This study was undertaken to validate potential biomarkers of exposure and effects due to chemical contaminants in breedingcolonies of the Great Blue Heron and the Black-crowned Night-Heron on the St. Lawrence River. Eggs and fledglings from both species were collected from many colonies along theRiver. The fledglings from colonies in freshwater and brackishwater were more contaminated by mercury and PCBs than those from estuarine and gulf colonies. With respect to fledglings ofthe two heron species, some morphometric and blood biochemicalmeasurements, including plasma thyroid hormones and retinol, were significantly different among colonies. Significant differences were also observed in liver retinoids, EROD and porphyrins among colonies. The results of this study suggestthat plasma retinoids and thyroid hormones are good biomarkersof exposure and effects, and are sufficiently sensitive to reflect local and regional variations in contamination. Along with the measure of contaminants in egg and plasma, they constitute non-invasive biomarkers which represent an importantcriteria for long term monitoring of wildlife species. It is concluded that the Great Blue Heron is an appropriate sentinelspecies in the surveillance network for the St. Lawrence River.     

South Africa's arid and semiarid rangelands: Why are they changing and can they be restored?

Since the mid-19th century settled livestock ranching has been the major form of land use in South Africa, occupying 68% of the land surface. Decreases in livestock densities and ranch numbers during the past century imply that carrying capacities for domestic herbivores are falling. Differences in carbon isotope signals with soil depth and abrupt shifts in dominant plant species across ranch boundaries reveal that southern African rangelands are changing. Case studies suggest ways to control altered grassland composition, bush encroachment in arid savanna, and dominance by toxic and halophytic shrubs in arid shrublands. But climatic and biological factors constrain rates of passive recovery, and guidelines for active restoration are poor and techniques costly. Moreover, conservation of remaining good rangeland is seldom enforced, and economic considerations usually outweight the land user's desire to sustain diversity and productivity.     

Interactive effects of personality and organizational politics on contextual performance

The authors explored the process of evaluating contextual performance in the context of a politically charged atmosphere. They hypothesized that the negative relationship between perceptions of organizational politics and contextual performance is weaker among workers high in three of the Big Five model of personality dimensions—agreeableness, extraversion, and conscientiousness. Data were collected from a matched sample of 540 supervisors and subordinates employed in the private sector. Results indicated that the interaction of politics and the personality dimension of agreeableness explained a significant incremental amount of variance in the interpersonal facilitation facet of contextual performance. These findings demonstrate the need to consider both the situation and the person as antecedents of contextual performance. Copyright © 2002 John Wiley & Sons, Ltd.     

The impact of a large‐scale traumatic event on individual and organizational outcomes: exploring employee and company reactions to September 11, 2001

Much of the literature on stress and organizational outcomes has focused on organizational factors and has ignored extraorganizational stressors that lead to perceived stress. However, research in other fields and recent studies in management suggests that acute‐extraorganizational stressors, such as traumatic events, may have potentially negative and costly implications for organizations. This study tests a theoretical model of traumatic stress and considers the relationship between strain from an acute‐extraorganizational stressor, the terrorist attack on September 11, 2001, and absenteeism. Using a sample of 108 MBA and MPA students, this study suggests that strain caused by an acute‐extraorganizational stressor can have important consequences for organizations. Namely, employees who report more strain from a traumatic life event are more likely to be absent from work in the weeks following the event. Copyright © 2002 John Wiley & Sons, Ltd.     

Exploring the role of hope in job performance: results from four studies

According to Snyder's hope theory, high hope individuals possess more goal‐related strategies and are more motivated to achieve their goals than their low hope counterparts. Therefore, we examined the relationship between hope and job performance using three different samples of employees of different job levels and industries. We found that more hopeful sales employees, mortgage brokers, and management executives had higher job performance, as measured a year later, even after controlling for their self‐efficacy and cognitive ability. In a fourth study, we examined if more hopeful employees attempt to solve problems differently than do those with less hope. Higher hope management executives produced more and better quality solutions to a work‐related problem, suggesting that hopefulness may help employees when they are confronted with problems and encounter obstacles at work. Copyright © 2007 John Wiley & Sons, Ltd.     

Feedback acceptance in developmental assessment centers: the role of feedback message,participant personality,and affective response to the feedback session

We investigated feedback acceptance by participants (N = 141) in an operational developmental assessment center (AC). Consistent with predictions based on self‐enhancement theory and the Affective Infusion Model, results indicated that higher assessor ratings were associated with higher feedback acceptance, and this relationship was partially mediated by the participant's affective reaction to the feedback session. Participants' self‐ratings of their AC performance did not affect this relationship suggesting no support for our prediction based on self‐verification theory. We also investigated the role of participants' self‐ratings of agreeableness, extraversion, and emotional stability in feedback acceptance by testing specific moderated mediation hypotheses. Extraversion was related to feedback acceptance through the affective reaction to the feedback session. Agreeableness moderated the affective reaction to the feedback session and feedback acceptance relationship such that there was a strong relationship between affective reaction and feedback acceptance for highly agreeable participants, but no relationship for low agreeable individuals. For low agreeable individuals, there was a positive direct relationship between the assessor ratings and feedback acceptance which was not observed for highly agreeable individuals. The hypothesized role of emotional stability in predicting feedback acceptance was not supported. Implications for the delivery of feedback in developmental ACs are discussed in light of these findings. Copyright © 2008 John Wiley & Sons, Ltd.