Identifying target reference points for harvesting assessment-limited wildlife populations: a case study.

Prioritization of sediment management alternatives using stochastic multicriteria acceptability analysis

Applied ecology has traditionally approached management problems through a simplified, single-species lens. Repeated failures of single-species management have led us to a new paradigm - managing at the ecosystem level. Ecosystem management involves a complex array of interacting organisms, processes and scientific disciplines. Accounting for interactions, feedback loops and dependencies between ecosystem components is therefore fundamental to understanding and managing ecosystems. We provide an overview of the main types of ecosystem models and their uses, and discuss challenges related to modelling complex ecological systems. Existing modelling approaches typically attempt to do one or more of the following: describe and disentangle ecosystem components and interactions; make predictions about future ecosystem states; and inform decision making by comparing alternative strategies and identifying important uncertainties. Modelling ecosystems is challenging, particularly when balancing the desire to represent many components of an ecosystem with the limitations of available data and the modelling objective. Explicitly considering different forms of uncertainty is therefore a primary concern. We provide some recommended strategies (such as ensemble ecosystem models and multi-model approaches) to aid the explicit consideration of uncertainty while also meeting the challenges of modelling ecosystems.

Uncertainty in pest control thresholds: Application to chemical control of corn earworm on soybean

Random fatigue of plane frames via lumped damage mechanics

We present a statistical framework for model calibration and uncertainty estimation for complex deterministic models. A Bayesian approach is used to combine data from observations, the deterministic model, and prior parameter distributions to obtain forecast distributions. A case study is presented in which the statistical framework is applied using the hydrogeochemical model (MAGIC) for an assessment of recovery from acidification of soils and surface waters at a long-term study site in Norway under different future acid deposition conditions. The water quality parameters are coupled with a simple dose-response model for trout population health. Uncertainties in model output parameters are estimated and forecast results are presented as probability distributions for future water chemistry and as probability distributions of future healthy trout populations. The forecast results are examined for three different scenarios of future acid deposition corresponding to three different emissions control strategies for Europe. Despite the explicit consideration of uncertainties propagated into the future forecasts, there are clear differences among the scenarios. The case study illustrates how inclusion of uncertainties in model predictions can strengthen the inferences drawn from model results in support of decision making and assessments.

This paper reviews the principles of scenario-based planning and illustrates an application of this approach in a study of a regional water supply and demand in northeastern Illinois. The scenario-based planning has been adopted over the traditional approaches because the scenario approach facilitates an explicit consideration of uncertainty in both supply and demand. An important component of the study was the development of scenario-based forecasts of water demand for major user sectors and geographical subareas within the 11-county region which, includes the city of Chicago and 250 municipalities. The study revealed that the increase in total withdrawals in 2050, under baseline scenario, would be 530 mgd (millions of gallons per day) (36 %) and could reach as high as 949 mgd (64 %) under high demand growth scenario. Thus, meeting these additional demands would require large capital outlays for water infrastructure and would likely have significant impacts on some of the regional sources of water supply...

Knowledge of the effects of hunting and environmental influences on survival of eastern wild turkeys ( Meleagris gallopavo silvestris ) is critical to managers setting fall and spring hunting seasons. Research has shown improper season frameworks can result in unsustainably high harvest rates of adult males, affect male age structure, and result in lower hunter satisfaction. Our objectives were to estimate survival rates of males, identify causes of mortality, and relate hunting and environmental influences to male turkey survival. We captured and radio‐tagged male wild turkeys in Virginia ( n = 204) and West Virginia ( n = 197), USA, during 2004–2007. We used staggered entry Kaplan‐Meier models to estimate survival and Cox Proportional Hazards Models to estimate effects of predictor variables on survival. Survival was estimated for 3 distinct periods of interest: annual, fall hunting (October–January), and spring hunting (April–May). The leading causes of mortalities (209 turkeys) were legal spring harvest (42%), predation (25%), and poaching (17%). Only 8 turkeys (4%) were taken during fall hunting seasons. Confidence intervals for annual survival of 2 year‐old and 3+ year‐old turkeys overlapped; therefore, we combined adult ages into a single category (2+). Adult (2+) annual survival was 0.63 (95% CI = 0.58–0.69) and the harvest rate was 25% (95% CI = 20–29%) for the combined states. Annual survival rates for adults (2+) were greater than in most other published studies, whereas adult (2+) spring harvest rates were lower. For juvenile males, annual survival was 0.74 (95% CI = 0.68–0.79) and spring harvest rate was 7% (95% CI = 3–11%). High juvenile and adult (2+) survival may have been related to low harvest rates. Adult turkeys (2+) had 46% greater risk of dying than one‐year‐old birds and were 3.7 times more likely to be harvested than juveniles. Age, a relative phenology index (RPI; spring green‐up), and white oak ( Quercus alba ) acorn production were included in the top models for annual survival, spring season survival, and spring harvest risk. Increasing RPI (more foliage) decreased mortality risk and greater white oak ( Quercus alba ) acorn abundance increased mortality risk. Across 4 regions in the 2 states, fall survival was high (0.90, 95% CI = 0.87–0.93). The impact of fall hunting on males in Virginia was low (5% harvest rate, 95% CI = 0–9%). Overall, spring harvest had the greatest effect on male survival, although those effects were moderated by the previous fall white oak crop and the onset of green‐up in the spring.

Developing risk equivalent data-rich and data-limited harvest strategies

BackgroundWildlife populations are difficult to monitor directly because of costs and logistical challenges associated with collecting informative abundance data from live animals. By contrast, data on harvested individuals (e.g., age and sex) are often readily available. Increasingly, integrated population models are used for natural resource management because they synthesize various relevant data into a single analysis.Methodology/Principal FindingsWe investigated the performance of integrated population models applied to black bears (Ursus americanus) in Minnesota, USA. Models were constructed using sex-specific age-at-harvest matrices (1980–2008), data on hunting effort and natural food supplies (which affects hunting success), and statewide mark–recapture estimates of abundance (1991, 1997, 2002). We compared this approach to Downing reconstruction, a commonly used population monitoring method that utilizes only age-at-harvest data. We first conducted a large-scale simulation study, in which our integrated models provided more accurate estimates of population trends than did Downing reconstruction. Estimates of trends were robust to various forms of model misspecification, including incorrectly specified cub and yearling survival parameters, age-related reporting biases in harvest data, and unmodeled temporal variability in survival and harvest rates. When applied to actual data on Minnesota black bears, the model predicted that harvest rates were negatively correlated with food availability and positively correlated with hunting effort, consistent with independent telemetry data. With no direct data on fertility, the model also correctly predicted 2-point cycles in cub production. Model-derived estimates of abundance for the most recent years provided a reasonable match to an empirical population estimate obtained after modeling efforts were completed.Conclusions/SignificanceIntegrated population modeling provided a reasonable framework for synthesizing age-at-harvest data, periodic large-scale abundance estimates, and measured covariates thought to affect harvest rates of black bears in Minnesota. Collection and analysis of these data appear to form the basis of a robust and viable population monitoring program.

Developing socioeconomic indicators for an ecosystem-based fisheries management approach: An application to the Korean large purse seine fishery

Maintenance of overall ecosystem complexity is perceived as critical to the sustainability of ecosystem use. The development of an operational basis for an ecosystem approach to fisheries, however, faces many difficulties. On the research side, the challenge is in defining proper long-term, ecosystem-related objectives; determining meaningful reference values and indicators for desirable or undesirable states of the ecosystem; and developing appropriate data collection, analytical tools and models. The “viability” concept developed in economics by Jean-Pierre Aubin can be used to assist in the definition, selection of, and interaction among long-term objectives at an ecosystem level. It recognizes that ecosystems are complex assemblages of interacting and self-organizing natural and human components that cannot be predicted. Viability models define an ensemble of “viable states”, in contrast to undesirable states defined as such by ecological, economic, and/or social constraints. These constraints can be derived from fisheries objectives, conservation principles, scientific results of modelling, or precautionary principles, and correspond to limit reference points to be avoided. Viability theory does not attempt to choose any “optimal solution” according to given criteria, but selects “viable evolutions”. These evolutions are compatible with the constraints in the sense that they satisfy them at each time and can be delineated by the viability kernel. The southern Benguela marine ecosystem is presented as a first attempt for the application of this theory. In defining ecosystem-based objectives (and related issues such as target reference points), it seems more difficult to reach consensus among stakeholders on what is desirable than on what is undesirable (e.g. biological or economic collapse, species extinction, displacement of local rural communities). Expressed in the negative form or as limit reference points, ecosystem-based constraints can be considered simultaneously with current target reference points, such as maximum sustainable yield, using viability models. The viability approach can help to progressively integrate ecosystem considerations, such as conservation, into fisheries management.

This paper examines capacity-building measures used by the health sector relevant to natural resource management (NRM) using the delivery of two programs in Australia through its recently formalized 56 community-based regional NRM Boards as a reference point. The delivery of NRM outcomes through devolved governance arrangements has been hampered by inadequate capacity in other countries (e.g., New Zealand, Canada). The inherent complexities of NRM, coupled with professional “comfort zones,” often limit actors from looking to other sectors confronting similar issues. This paper summarizes findings from ∼70 sources in health reviewing nine major capacity-building measures. The outcomes of research evaluating the relative benefits and disbenefits of applying these measures are discussed. The paper identifies several opportunities to trial some of these measures in NRM.

In hydraulic position servo systems, the parametric uncertainties, the inherent nonlinear characters of hydraulic system and the large variations of payload affect the tracking precision and robust performance. A disturbance observer based control scheme and an integral extended state observer based nonlinear control scheme called active disturbance rejection control are proposed in this paper. A comparison study of these two disturbance rejection control strategies for hydraulic position servo systems has been undertaken. Simulation and experimental results show that the active disturbance rejection control is much superior in dealing with system dynamic uncertainties and disturbances.

Population dynamics and stock assessment of Red snapper (Lutjanus johnii) in the Bay of Bengal Bangladesh waters

In the policy context, managing grouper and snapper fisheries resources for sustainability is a big challenge due to the complexity of small-scale fisheries in Saleh Bay. This study implemented two analytical methods: length-based analysis and ecosystem approach to fisheries assessment to evaluate the performance of the implementation of the grouper and snapper fisheries management in Saleh Bay. The results showed after policy implementation, the mean length of species has been slightly larger and three species already reached the spawning potential ratio (SPR) target reference point. However, two of the 11 species regulated had SPR values below the limit reference point, which indicated that these species are currently fished at unsustainable levels. Overall, the assessment of fishery risk index indicated the risk status of this fisheries in the category of moderate risk, 1.185, in which two dimensions need to be improved: socio-economy and habitat. Therefore, this study highlighted leverage points to achieve ‘good’ performance level, such as socialization program intensively, enforcing regulation to provincial regulation, strengthening the surveillance and law enforcement of destructive fishing practices, empowerment of local institutions by co-management, and rehabilitation of coral reef ecosystems.