MODELLING STOCK DYNAMICS IN THE SOUTHERN BENGUELA ECOSYSTEM FOR THE PERIOD 1978–2002

An ecosystem model of the southern Benguela was fitted to available time-series data for the period 1978–2002, to explore how changes in target fish populations in this ecosystem can be attributed to feeding interaction terms and population control patterns, the impact of fishing, and environmental forcing. Fishing patterns were estimated to explain only 2–3&#37 of the variability in the time-series, whereas an estimated productivity forcing pattern applied to phytoplankton explained 4–12&#37 of the variance represented by the sum of squares. Model settings describing prey vulnerability to their predators could explain around 40&#37 of the variability in the time-series. Modelled stock dynamics in the southern Benguela ecosystem more closely represent observed timeseries when wasp-waist control by small pelagic fish is simulated. Overall, model simulations suggest that almost half the variance in the time-series can be explained based on a combination of fishing, vulnerability settings and productivity patterns. Variation in mortalities and prey preferences over time, as well as model fits in relation to available effort series, are discussed. The study advances a model with improved parameterization and credibility to assist with an ecosystem approach to South African fisheries management. Afr. J. mar. Sci. 26: 179–19

Sharing the transformation: Public relations and the uae come of age

© 2009 Taylor and Francis. Much like the country itself, the practice of public relations in the United Arab Emirates (UAE) has undergone a profound evolution during its short history of 30 years. As the country has grown, so too has the practice of public relations. Once no agencies existed, but today global multinational public relations firms have established a presence in the UAE, some with an equity relationship with their local partners, some as fully owned branches of global firms based in the United States or Europe, and others through affiliates. Companies like Team: Young and Rubicam, Gulf Hill and Knowlton, and Burston-Marsteller operate alongside local, smaller companies, competing for the same dollars and dirhams

Spontaneous Hemarthrosis of the Knee - Late Complication of Flexible Femur Nailing: A Case Report.

We present a case report of acute spontaneous knee hemarthosis due to erosion of the nail through the knee joint capsule in a boy, seven months following retrograde flexible nailing for fractured femur. Careful positioning of the location of the insertion site of flexible nails and proper nail tip management are important to avoid this rare late complication

Hypnotic imagery as an adjunct to the treatment of PTSD and extreme distress

This client study of a 23-year old woman begins by exploring post-abortion distress in context with hypnosis, and identifies particular themes across symptoms that indicate that hypnosis may be an appropriate adjunct to therapy for this problem. For treatment a three-phase framework was used as proposed by Brown (1995) for PTSD. Symptom changes were monitored throughout the course of therapy in a multiple-baseline design. The client also completed pre- and post-therapy questionnaires. The therapeutic outcome is described with reference to data collected from weekly monitoring and from written feedback regarding the client’s own feelings about the therapy. The results indicate that the therapeutic interventions improved specific symptoms as well as general mental health and it is concluded that hypnosis may be a particularly appropriate adjunct to therapy for post-abortion distress

Rigorous confidence intervals for critical probabilities

We use the method of Balister, Bollobas and Walters to give rigorous 99.9999% confidence intervals for the critical probabilities for site and bond percolation on the 11 Archimedean lattices. In our computer calculations, the emphasis is on simplicity and ease of verification, rather than obtaining the best possible results. Nevertheless, we obtain intervals of width at most 0.0005 in all cases

Dominated Splitting and Pesin's Entropy Formula

Let $M$ be a compact manifold and $f:\,M\to M$ be a $C^1$ diffeomorphism on $M$. If $\mu$ is an $f$-invariant probability measure which is absolutely continuous relative to Lebesgue measure and for $\mu$ $a.\,\,e.\,\,x\in M,$ there is a dominated splitting $T_{orb(x)}M=E\oplus F$ on its orbit $orb(x)$, then we give an estimation through Lyapunov characteristic exponents from below in Pesin's entropy formula, i.e., the metric entropy $h_\mu(f)$ satisfies $$h_{\mu}(f)\geq\int \chi(x)d\mu,$$ where $\chi(x)=\sum_{i=1}^{dim\,F(x)}\lambda_i(x)$ and $\lambda_1(x)\geq\lambda_2(x)\geq...\geq\lambda_{dim\,M}(x)$ are the Lyapunov exponents at $x$ with respect to $\mu.$ Consequently, by using a dichotomy for generic volume-preserving diffeomorphism we show that Pesin's entropy formula holds for generic volume-preserving diffeomorphisms, which generalizes a result of Tahzibi in dimension 2

Implications of existing local (mal)adaptations for ecological forecasting under environmental change

Standing genetic variation represents a genetic load on population fitness but can also support a rapid response to short‐term environmental change, and the greatest potential source of such standing genetic variation typically exists among locally adapted populations living along an environmental gradient. Here we develop a spatially‐explicitly simulation model to quantify the contribution of existing genetic variation arising from migration‐mutation‐selection‐drift balance to time to extinction under environmental change. Simulations reveal that local adaptation across a species range associated with an underlying environmental gradient could extend time to extinction by nearly three–fold irrespective of the rate of environmental change. The potential for pre‐adapted alleles to increase the rate of adaptation changes the relative importance of established extinction risk factors, in particular it reduced the importance of the breadth of environmental tolerance and it increased the relative importance of fecundity. Although migration of preadapted alleles generally increased persistence time, it decreased it at rates of environmental change close to the critical rate of change by creating a population bottleneck, which ultimately limited the rate at which de novo mutations could arise. An analysis of the extinction dynamics further revealed that one consequence of gene flow is the potential to maximise population growth rate in at least part of the species range, which is likely to have consequences for forecasting the consequences of ecological interactions. Our study shows that predictions of persistence time change fundamentally when existing local adaptations are explicitly taken into account, underscoring the need to preserve and manage genetic diversity