Optimal fishery policy for size-specific,density-dependent population models

Optimal harvest policy is derived for a size-specific population model based on the continuity equation. In this model both growth and recruitment rates can depend on either the number of individuals of specific sizes in the population or the level of food available. Necessary conditions for values of fishing pressure and size limit that maximize the present value of the resource are obtained and are interpreted in economic terms. The general solution obtained here reduces to solutions obtained previously for some special cases: the single age-class model, and the linear age-dependent model. Solutions involving constant fishery policy are sought for several different, specific versions of the general model. In each of these versions a constant policy solution is not optimal. This implies that for a general, realistic model the policy that maximizes present value is a time-varying or pulse fishing policy. The theoretical and practical implications of the results are discussed in the light of existing results.     

Approach to equilibrium in age structured populations with an increasing recruitment process

This paper considers a model for the dynamics of an age structured population subject to a density dependent factor which regulates the recruitment. Certain properties of biological interest are obtained and the stability of the equilibrium age distributions is investigated. Finally some applications to known fishery models are considered.Work done under the contract 80.02333.01 of C.N.R.     

Challenges in genetic resources policy making: some lessons from participatory policy research with a special reference to Ethiopia

It is widely recognized that developing countries lack technical and institutional capacity to effectively implement genetic resources policy. This has led Bioversity International (the then IPGRI) to initiate a project called Genetic Resources Policy Initiative (GRPI) in six countries (Ethiopia, Egypt, Zambia, Peru, Vietnam and Nepal). Drawing from the literature and experiences of this project, this paper has attempted to document some of the lessons from the project and present the issues and challenges that need to be addressed for effective genetic resources policy. Recognizing its cross-cutting nature, the paper has argued that genetic resources policy has to be part of the broader development agenda to effectively deal with trade-offs and harmonize the conflicts. Essentially, the important policy question is to strike the balance and simultaneously promote the diversity of genetic resources and welfare outcomes. The major thrust of GRPI has been the multi-disciplinary, -sectoral, and -stakeholder (3M) approach. Despite all its theoretical merits, its implementation has been a serious challenge in practice. This has, among others, been due to ‘‘A project for all is a project for none’’ dilemma. Engaging decision makers in 3M deliberations has revealed that many of them tend to think that maintaining genetic diversity promotes traditional farming and retards agricultural development. Clearly, addressing each of these challenges and policy loopholes requires innovation in a diversity of institutions.     

Membrane transport models with fast and slow reactions: General analytical solution for a single relaxation

Summary Membrane transport models are usually expressed on the basis of chemical kinetics. The states of a transporter are related by rate constants, and the time-dependent changes of these states are given by linear differential equations of first order. To calculate the time-dependent transport equation, it is necessary to solve a system of differential equations which does not have a general analytical solution if there are more than five states. Since transport measurements in a complex system rarely provide all the time constants because some of them are too rapid, it is more appropriate to obtain approximate analytical solutions, assuming that there are fast and slow reaction steps. The states of the fast steps are related by equilibrium constants, thus permitting the elimination of their differential equations and leaving only those for the slow steps. With a system having only two slow steps, a single differential equation is obtained and the state equations have a single relaxation. Initial conditions for the slow reactions are determined after the perturbation which redistribute the states related by fast reactions. Current and zero-trans uptake equations are calculated. Curve fitting programs can be used to implement the general procedure and obtain the model parameters.     

Dynamical stabilization of grazing systems: An interplay among plant-water interaction, overgrazing and a threshold management policy

In a plant-herbivore system, a management strategy called threshold policy is proposed to control grazing intensity where the vegetation dynamics is described by a plant-water interaction model. It is shown that this policy can lead the vegetation density to a previously chosen level under an overgrazing regime. This result is obtained despite both the potential occurrence of vegetation collapse due to overgrazing and the possibility of complex dynamics sensitive to vegetation initial densities and parameter uncertainties.     

An Australian Brain Bank: a critical investment with a high return!

Research into neuropsychiatric disorders, including alcohol-related problems, is limited in part by the lack of appropriate animal models. However, the development of new technologies in pathology and molecular biology means that many more questions can be addressed using appropriately stored human brain tissues. The New South Wales Tissue Resource Centre (TRC) in the University of Sydney (Australia) is a human brain bank that can provide tissues to the neuroscience research community studying alcohol-related brain disorders, schizophrenia, depression and bipolar disorders. Carefully standardised operational protocols and integrated information systems means that the TRC can provide high quality, accurately characterised, tissues for research. A recent initiative, the pre-mortem donor program called "Using our Brains", encourages individuals without neuropsychiatric illness to register as control donors, a critical group for all research. Community support for this program is strong with over 2,000 people registering their interest. Discussed herein are the protocols pertaining to this multifaceted facility and the benefits of investment, both scientific and financial, to neuroscience researchers and the community at large.     

Environmentally engaged research: An interview with Paul Adam

For over three decades, New South Wales ecologist Paul Adam has worked to promote the study and conservation of native ecosystems and has served on scores of agency and NGO committees. Here, Paul provides some insight into what motivates such a sustained contribution.     

Enrichment of fertilizers with zinc: An excellent investment for humanity and crop production in India

Micronutrient malnutrition is a growing concern in the developing world, resulting in diverse health and social problems, such as mental retardations, impairments of the immune system and overall poor health. In recent years, the zinc (Zn) deficiency problem has received increasing attention and appears to be the most serious micronutrient deficiency together with vitamin A deficiency. Zinc deficiency is particularly widespread among children and represents a major cause of child death in the world. In countries where Zn deficiency is well documented as an important public health problem, cereal-based foods are the predominant source of daily calorie and protein intake. Because the concentration of Zn in cereal crops is inherently very low, growing cereals on potentially Zn-deficient soils further decreases grain Zn concentrations. It is, therefore, not surprising that high Zn deficiency incidence in humans occurs predominantly on areas where soils are deficient in plant-available Zn, as shown in many Southeast Asian countries. India has some of the most Zn-deficient soils in the world. Nearly 50% of cultivated soils in India are low in plant-available Zn; these soils are under intensive cultivation of wheat and rice with no or little application of Zn fertilizers. Consequently, cereal crops grown on such Zn-deficient soils contribute only marginally to daily Zn intake. In the rural areas of India, rice and wheat contributes nearly 75% of the daily calorie intake. These facts clearly point to an urgent need for improved Zn concentration of cereal grains in India. Recent calculations indicate that biofortification (enrichment) of rice and wheat grain with Zn, for example by breeding, may save lives of up to 48,000 children in India annually. Breeding new cereal genotypes for high grain Zn concentration is the most realistic and cost-effective strategy to address the problem. However, this strategy is a long-term one, and the size of plant-available Zn pools in soils may greatly affect the capacity of Zn-efficient (biofortified) cultivars to take up Zn and accumulate it in grains. Therefore, application of Zn-containing fertilizers represents a quick and effective approach to biofortifying cereal grains with Zn, thus being an excellent complementary tool to the breeding strategy for successful biofortification of cereals with Zn. Increasing evidence is available from field trials showing that soil and/or foliar application of Zn fertilizers improves grain Zn concentration up to 2- or 3-fold. In the countries where Zn deficiency is both a public health issue and an important soil constraint to crop production, like in India, enrichment of widely applied fertilizers with Zn would be an excellent investment for improving grain Zn while contributing to increased crop production. Recent work by the scientists of the Indian Agricultural Research Institute indicates that the use of Zn-enriched urea in rice and wheat significantly improves both grain Zn concentration and grain yield. It is obvious that enrichment of widely applied fertilizers with Zn and/or foliar application of Zn fertilizers appear to be a high priority with the strongest potential to alleviate Zn deficiency-related problems in India. A Government action and policy plan for enrichment of selected major fertilizers with Zn is required urgently.     

Making parks make a difference: poor alignment of policy,planning and management with protected-area impact,and ways forward

Policy and practice around protected areas are poorly aligned with the basic purpose of protection, which is to make a difference. The difference made by protected areas is their impact, defined in program evaluation as the outcomes arising from protection relative to the counterfactual of no protection or a different form of protection. Although impact evaluation of programs is well established in fields such as medicine, education and development aid, it is rare in nature conservation. We show that the present weak alignment with impact of policy targets and operational objectives for protected areas involves a great risk: targets and objectives can be achieved while making little difference to the conservation of biodiversity. We also review potential ways of increasing the difference made by protected areas, finding a poor evidence base for the use of planning and management ‘levers’ to better achieve impact. We propose a dual strategy for making protected areas more effective in their basic role of saving nature, outlining ways of developing targets and objectives focused on impact while also improving the evidence for effective planning and management.     

Population Dynamics Modelling in an Hierarchical Arborescent River Network: An Attempt with Salmo trutta

The balance between births and deaths in an age-structured population is strongly influenced by the spatial distribution of sub-populations. Our aim was to describe the demographic process of a fish population in an hierarchical dendritic river network, by taking into account the possible movements of individuals. We tried also to quantify the effect of river network changes (damming or channelling) on the global fish population dynamics. The Salmo trutta life pattern was taken as an example for.We proposed a model which includes the demographic and the migration processes, considering migration fast compared to demography. The population was divided into three age-classes and subdivided into fifteen spatial patches, thus having 45 state variables. Both processes were described by means of constant transfer coefficients, so we were dealing with a linear system of difference equations. The discrete case of the variable aggregation method allowed the study of the system through the dominant elements of a much simpler linear system with only three global variables: the total number of individuals in each age-class.From biological hypothesis on demographic and migratory parameters, we showed that the global population dynamics of fishes is well characterized in the reference river network, and that dams could have stronger effects on the global dynamics than channelling.     

Conservation,protected areas and the global economic system: how debt,trade, exchange rates,inflation and macroeconomic policy affect biological diversity

The main characteristics of the dominant economic system, including the increasing use of markets and money are described. The global system has expanded trade, including international trade, and production tremendously. While this system has the potential to favour nature conservation, in practice the opposite has occurred. Difficulties raised for conservation of biodiversity by short-term economic crises such as deficits in a country's international payments, the adoption of policies for structural economic adjustment, international capital flows, international loans and foreign aid as well as debt-for-nature swaps are discussed. As explained, it is politically difficult in market economies to support nature conservation at the expense of economic growth and as more economies develop and become market economies this problem spreads. Given global interdependence of nations, an important issue is the distribution of net benefits from biodiversity conservation between developed and less developed countries. Possible distributions of benefits and related issues are discussed. In conclusion, the importance of political lobbying by nature conservation groups in developed market economies is emphasised as a means of ensuring correction of market failures. Unfortunately, no economic system is likely to prove satisfactory in itself in conserving biodiversity so political action by conservationists is always required.     

Donor Perspectives on Issues Associated with Donation of Genetic Samples and Information: An Australian Viewpoint

This paper provides a legal overview of key issues associated with donation of genetic samples and information from a donor perspective. In particular, it addresses the property status of samples as well as issues in respect of consent, privacy, commercialisation and benefit sharing. The paper highlights the need for appropriate protection and safeguards for individuals, but also, importantly, for understanding what donors actually think and want in terms of genetic research and the use of their samples and information. The paper seeks to emphasise the importance of transparency and accountability in the conduct of research in order to maximise donor participation and confidence and public trust in general.

An Exploratory Investigation of Genetic Linkage with Body Composition and Fatness Phenotypes: The Québec Family Study

In the present investigation, we have attempted to identify regions of the genome in which “obesity genes” potentially reside using robust sib-pair linkage analysis. Data were collected on 1,628 individuals in 301 nuclear families residing in the environs of Québec City during the period 1978–1981. In addition to traditional blood group antigens and enzyme polymorphisms, several phenotypes in the obesity domain that are associated with increased morbidity were assessed, including measures relating to heaviness (i.e., the body mass index), body composition and nutrient partitioning (i.e., % body fat), and regional fat distribution without and with standardization for total fat mass (i.e., the sum of six skinfold thicknesses, and the ratio of the sums of trunk to extremity skinfold thicknesses). Three consistent patterns of potential linkage relationships with obesity phenotypes were revealed in these data, involving the marker loci adenosine deaminase, the Kell blood group antigen, and esterase D, which identify chromosomal regions 20q13, 7q33, and 13q14, respectively. Other potential linkages also were identified in the short arm of chromosome 1, interesting because of the presence of the db and fa loci on homologous regions of chromosome 1 in mouse and rat models of obesity, respectively. Each of the tentative linkage relationships reported here warrant follow-up using alternative methods and require replication in independent studies.     

Multiscale analysis of collective motion and decision-making in swarms: An advection-diffusion equation with memory approach

We propose a (time) multiscale method for the coarse-grained analysis of collective motion and decision-making in self-propelled particle models of swarms comprising a mixture of ‘naïve’ and ‘informed’ individuals. The method is based on projecting the particle configuration onto a single ‘meta-particle’ that consists of the elongation of the flock together with the mean group velocity and position. We find that the collective states can be associated with the transient and asymptotic transport properties of the random walk followed by the meta-particle, which we assume follows a continuous time random walk (CTRW). These properties can be accurately predicted at the macroscopic level by an advection-diffusion equation with memory (ADEM) whose parameters are obtained from a mean group velocity time series obtained from a single simulation run of the individual-based model.     

Excess mortality in persons with severe mental disorders: a multilevel intervention framework and priorities for clinical practice,policy and research agendas

Excess mortality in persons with severe mental disorders (SMD) is a major public health challenge that warrants action. The number and scope of truly tested interventions in this area remain limited, and strategies for implementation and scaling up of programmes with a strong evidence base are scarce. Furthermore, the majority of available interventions focus on a single or an otherwise limited number of risk factors. Here we present a multilevel model highlighting risk factors for excess mortality in persons with SMD at the individual, health system and socio‐environmental levels. Informed by that model, we describe a comprehensive framework that may be useful for designing, implementing and evaluating interventions and programmes to reduce excess mortality in persons with SMD. This framework includes individual‐focused, health system‐focused, and community level and policy‐focused interventions. Incorporating lessons learned from the multilevel model of risk and the comprehensive intervention framework, we identify priorities for clinical practice, policy and research agendas.