Comparing species and ecosystem-based estimates of fisheries yields

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Fisheries Research 111 (2011): 139-144, doi:10.1016/j.fishres.2011.07.009.Three methods are described to estimate potential yields of commercial fish species: (i) single-species calculation of maximum sustainable yields, and two ecosystem-based methods derived from published results for (ii) energy flow and for (iii) community structure. The requirements imposed by food-web fluxes, and by patterns of relative abundance, provide constraints on individual species. These constraints are used to set limits to ecosystem-based yields (EBY); these limits, in turn, provide a comparison with the usual estimates of maximum sustainable yields (MSY). We use data on cod and haddock production from Georges Bank for the decade 1993-2002 to demonstrate these methods. We show that comparisons among the three approaches can be used to demonstrate that ecosystem based estimates of yields complement, rather than supersede, the single-species estimates. The former specify the significant changes required in the rest of the ecosystem to achieve a return to maximum sustainable levels for severely depleted commercial fish stocks. The overall conclusion is that MSY defines changes required in particular stocks, whereas EBY determines the changes required in the rest of the ecosystem to realize these yields. Species specific MSY only has meaning in the context of the prey, predators and competitors that surround it.We acknowledge NSF awards OCE081459 (to DJG) and OCE0814474 (to JHS)

Deterministic Partial Differential Equation Model for Dose Calculation in Electron Radiotherapy

Treatment with high energy ionizing radiation is one of the main methods in modern cancer therapy that is in clinical use. During the last decades, two main approaches to dose calculation were used, Monte Carlo simulations and semi-empirical models based on Fermi-Eyges theory. A third way to dose calculation has only recently attracted attention in the medical physics community. This approach is based on the deterministic kinetic equations of radiative transfer. Starting from these, we derive a macroscopic partial differential equation model for electron transport in tissue. This model involves an angular closure in the phase space. It is exact for the free-streaming and the isotropic regime. We solve it numerically by a newly developed HLLC scheme based on [BerCharDub], that exactly preserves key properties of the analytical solution on the discrete level. Several numerical results for test cases from the medical physics literature are presented.Comment: 20 pages, 7 figure

Complex network analysis of wind tunnel experiments on the passive scalar dispersion in a turbulent boundary layer

In this work, data of passive scalar plumes in a turbulent boundary layer are investigated. The experiments are performed in a&nbsp;wind tunnel where a passive scalar is injected through an L-shaped tube. Two source configurations&nbsp;are analysed for two different tube diameters. The passive scalar concentration is then measured at different distances from the source and wall-normal locations. By exploiting the recent advances of complex networks theory, the concentration time-series are mapped into networks, through the visibility algorithm. The resulting networks inherit the temporal features of the mapped time-series, revealing non-trivial information about the underlying transport process. This work represents an example of the great potentialities of the complex network approach for the analysis of turbulent transport and mixing.</p

The effects of participation level on recidivism: a study of drug treatment courts using propensity score matching

Abstract Background: Empirical evidence has suggested that drug treatment courts (DTCs) reduce re-arrest rates. However, DTC program completion rates are low and little is known about the effectiveness of lower levels of program participation. Objectives: We examined how DTC program referral, enrollment without completion, and completion, affected re-arrest rates during a two-year follow-up. Research design: We used statewide North Carolina data from criminal courts merged with DTC data. Propensity score matching was used to select comparison groups based on demographic characteristics, criminal histories, and drug of choice (when available). Average treatment effects on the treated were computed. Measures: DTC participation levels included referral without enrollment, (n = 2,174), enrollment without completion (n = 954), and completion (n = 747). Recidivism measured as re-arrest on a substance-related charge, on a violent offense charge not involving an allegation of substance abuse, and on any charge (excluding infractions) was examined by felony and misdemeanor status during a two-year follow-up period

Exploratory randomised controlled trial of a mindfulness-based weight loss intervention for women

To explore the efficacy of a mindfulness-based weight loss intervention for women. Sixty-two women (ages 19-64; BMI 22.5-52.1) who were attempting to lose weight were randomised to an intervention or control condition. The former were invited to attend four 2-h workshops, the latter were asked to continue with their normal diets. Data were collected at baseline, 4 and 6 months. BMI, physical activity, mental health. At 6 months intervention participants showed significantly greater increases in physical activity compared to controls (p<.05) but no significant differences in weight loss or mental health. However, when intervention participants who reported 'never' applying the workshop principles at 6 months (n=7) were excluded, results showed both significantly greater increases in physical activity (3.1 sessions per week relative to controls, p<.05) and significantly greater reductions in BMI (0.96 relative to controls, equivalent to 2.32 kg, p<0.5). Reductions in BMI were mediated primarily by reductions in binge eating. Despite its brevity, the intervention was successful at bringing about change. Further refinements should increase its efficacy

Reconciling end-to-end and population concepts for marine ecosystems

Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Journal of Marine Systems 83 (2010): 99-103, doi:10.1016/j.jmarsys.2010.06.006.The inherent complexities in the structure and dynamics of marine food webs have led to two major simplifying concepts, a species-centric approach focused on physical processes driving the population dynamics of single species and a trophic-centric approach emphasizing energy flows through broad functional groups from nutrient input to fish production. Here we review the two approaches and discuss their advantages and limitations. We suggest that these concepts are complementary: their applications involve different time scales and distinct aspects of population and community resilience, but their integration is necessary for ecosystem-based managementWe acknowledge NOAA-CICOR award NA17RJ1233 (J.H. Steele) and NSF award OCE0217399 (D.J. Gifford)

End-to-end foodweb control of fish production on Georges Bank

Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Oxford University Press for personal use, not for redistribution. The definitive version was published in ICES Journal of Marine Science: Journal du Conseil 66 (2009): 2223-2232, doi:10.1093/icesjms/fsp180.The ecosystem approach to management requires the productivity of individual fish stocks to be considered in the context of the entire ecosystem. In this paper, we derive an annual end-to-end budget for the Georges Bank ecosystem, based on data from the GLOBEC program and fisheries surveys for the years 1993-2002. We use this budget as the basis to construct scenarios that describe the consequences of various alterations in the Georges Bank trophic web: reduced nutrient input, increased benthic production, removal of carnivorous plankton such as jellyfish, and changes in species dominance within fish guilds. We calculate potential yields of cod and haddock for the different scenarios, and compare the results with historic catches and estimates of maximum sustainable yield (MSY) from recent stock assessments. The MSYs of cod and haddock can be met if the fish community is restructured to make them the dominant species in their respective diet-defined guilds. A return to the balance of fish species present in the first half of the 20th century would depend on an increase in the fraction of primary production going to the benthos rather than to plankton. Estimates of energy flux through the Georges Bank trophic web indicate that rebuilding the principal groundfish species to their MSY levels requires restructuring of the fish community and repartitioning of energy within the food web.We acknowledge NOAA-CICOR award NA17RJ1233 (J.H. Steele) and NSF award OCE0217399 (D.J. Gifford and J.S. Collie)

Developing a holistic approach to the analysis of farmer decision-making: implications for adaptation policy and practice in developing countries

Smallholder farmers operate within a risky and uncertain context. In addition to climate variability and climate change, social, environmental, institutional, and market-related dynamics affect their agricultural decisions and ability to cope and adapt. In this paper, we develop and apply a set of framing questions to investigate the factors shaping farmer decision-making and how these are situated in pathways of response. Drawing on a literature review of decision-making for risk management, four questions are posed to frame enquiry: who makes livelihood decisions, why they are made, and how and when they are made. This approach conceptualises and explores household decision-making in a holistic manner, moving beyond previous studies that examine smallholder decisions through disciplinary boundaries (e.g. psychology, economics, risk management) or particular theoretical approaches (e.g. bounded rationality, theory of planned behaviour). The framing questions are used to design and interpret empirical evidence from Pratapgarh, a tribal-dominated rainfed district in southeast Rajasthan, India. The findings suggest that while resource ownership and access are the main drivers of decision-making, socio-cognitive factors such as perceived adaptive capacity and perceived efficacy to carry out adaptive actions are equally important factors mediating farmer responses. We also find that the holistic approach helps explain how personal motivations and individual perceptions of adaptive capacity interact with socioeconomic, climatic, and agro-ecological dynamics at local and regional scales to mediate risk perception and inform response behaviour. Making a case for mixed methods to investigate farmer decision-making holistically, this paper provides an approach that reflects the complex and iterative nature of real farmer decision-making and can be used by researchers, policymakers, and practitioners to better understand and describe decision making and to develop informed policies and interventions

Land use change from C3 grassland to C4 <em>Miscanthus</em>: effects on soil carbon content and estimated mitigation benefit after six years

To date, most Miscanthus trials and commercial fields have been planted on arable land. Energy crops will need to be grown more on lower grade lands unsuitable for arable crops. Grasslands represent a major land resource for energy crops. In grasslands, where soil organic carbon (SOC) levels can be high, there have been concerns that the carbon mitigation benefits of bioenergy from Miscanthus could be offset by losses in SOC associated with land use change. At a site in Wales (UK), we quantified the relatively short-term impacts (6 years) of four novel Miscanthus hybrids and Miscanthus × giganteus on SOC in improved grassland. After 6 years, using stable carbon isotope ratios (13C/12C), the amount of Miscanthus derived C (C4) in total SOC was considerable (ca. 12%) and positively correlated to belowground biomass of different hybrids. Nevertheless, significant changes in SOC stocks (0–30 cm) were not detected as C4 Miscanthus carbon replaced the initial C3 grassland carbon; however, initial SOC decreased more in the presence of higher belowground biomass. We ascribed this apparently contradictory result to the rhizosphere priming effect triggered by easily available C sources. Observed changes in SOC partitioning were modelled using the RothC soil carbon turnover model and projected for 20 years showing that there is no significant change in SOC throughout the anticipated life of a Miscanthus crop. We interpret our observations to mean that the new labile C from Miscanthus has replaced the labile C from the grassland and, therefore, planting Miscanthus causes an insignificant change in soil organic carbon. The overall C mitigation benefit is therefore not decreased by depletion of soil C and is due to substitution of fossil fuel by the aboveground biomass, in this instance 73–108 Mg C ha−1 for the lowest and highest yielding hybrids, respectively, after 6 years