Evaluation Of Alternative Management Strategies Research Articles

Incorporating stakeholders' values into environmental decision support: A Bayesian Belief Network approach

Participatory modelling increases the transparency of environmental planning and management processes and enhances the mutual understanding among different parties. We present a sequential probabilistic approach to involve stakeholders' views in the formal decision support process. A continuous Bayesian Belief Network (BBN) model is used to estimate population parameters for stakeholder groups, based on samples of individual value judgements. The approach allows quantification and visualization of the variability in views among and within stakeholder groups. Discrete BBN is populated with these parameters, to summarize and visualize the information and to link it to a larger decision analytic influence diagram (ID). As part of ID, the resulting discrete BBN element serves as a distribution-form decision criteria in probabilistic evaluation of alternative management strategies, to help find a solution that represents the optimal compromise in the presence of potentially conflicting objectives. We demonstrate our idea using example data from the field of marine spatial planning. However, this approach is applicable to many types of management cases. We suggest that by advancing the mutual understanding and concrete participation this approach can further facilitate the stakeholder involvement also during the various stages of the environmental management process.

Integrating Governance and Quantitative Evaluation of Resource Management Strategies to Improve Social and Ecological Outcomes

Abstract In this article, we examine how governance can be more effectively integrated with quantitative evaluation methods in applied resource management. Governance refers to how societies organize to make decisions in ways that influence management choices (e.g., harvest allocation), such as levels of participation, the inclusion of different types of knowledge, and legitimacy of processes that lead to decisions. Using a fisheries example, we show that a failure to consider the governance context for quantitative evaluation of alternative management strategies may lead to unexpected consequences or break points in decision-making, bias estimates of risk and returns from management choices, and mask the potential for undesirable social and ecological outcomes.

Could recent overfishing of New England groundfish have been prevented? A retrospective evaluation of alternative management strategies

We conducted a retrospective evaluation of alternative management strategies for stocks in the New England groundfish complex that have had recent history of target catches being set above the level that defines overfishing. In many cases the original target catches were unsustainable and would have resulted in stock collapses if the target catch had been removed. We evaluated (i) alternative harvest control rules, (ii) whether or not to do projections, (iii) whether the inputs to the projections (starting abundance and future recruitments) should be modified, and (iv) whether the target catches should be smoothed to prevent large changes from year to year. The greatest reductions in target catches resulted when no projections were done and the target catch was fixed over the period between assessments. Large reductions in target catches also occurred when a downward adjustment was made to the starting abundance in the projections based on the retrospective pattern. Neither approach alone was sufficient to prevent overfishing for most stocks, but when used in conjunction with one another or with an alternative control rule that reduced the target harvest rate as biomass fell below the target, the magnitude and frequency of overfishing was greatly reduced for most stocks. Attempts to adjust recruitment based on perceived changes over time were also effective for a few stocks, while attempts to smooth the target catches over often resulted in increases in the target catches.

Estimating the sustainability of towed fishing‐gear impacts on seabed habitats: a simple quantitative risk assessment method applicable to data‐limited fisheries

Summary Impacts of bottom fishing, particularly trawling and dredging, on seabed (benthic) habitats are commonly perceived to pose serious environmental risks. Quantitative ecological risk assessment can be used to evaluate actual risks and to help guide the choice of management measures needed to meet sustainability objectives. We develop and apply a quantitative method for assessing the risks to benthic habitats by towed bottom‐fishing gears. The method is based on a simple equation for relative benthic status (RBS), derived by solving the logistic population growth equation for the equilibrium state. Estimating RBS requires only maps of fishing intensity and habitat type – and parameters for impact and recovery rates, which may be taken from meta‐analyses of multiple experimental studies of towed‐gear impacts. The aggregate status of habitats in an assessed region is indicated by the distribution of RBS values for the region. The application of RBS is illustrated for a tropical shrimp‐trawl fishery. The status of trawled habitats and their RBS value depend on impact rate (depletion per trawl), recovery rate and exposure to trawling. In the shrimp‐trawl fishery region, gravel habitat was most sensitive, and though less exposed than sand or muddy‐sand, was most affected overall (regional RBS = 91% relative to un‐trawled RBS = 100%). Muddy‐sand was less sensitive, and though relatively most exposed, was less affected overall (RBS = 95%). Sand was most heavily trawled but least sensitive and least affected overall (RBS = 98%). Region‐wide, >94% of habitat area had >80% RBS because most trawling and impacts were confined to small areas. RBS was also applied to the region's benthic invertebrate communities with similar results. Conclusions. Unlike qualitative or categorical trait‐based risk assessments, the RBS method provides a quantitative estimate of status relative to an unimpacted baseline, with minimal requirements for input data. It could be applied to bottom‐contact fisheries world‐wide, including situations where detailed data on characteristics of seabed habitats, or the abundance of seabed fauna are not available. The approach supports assessment against sustainability criteria and evaluation of alternative management strategies (e.g. closed areas, effort management, gear modifications).

Population Dynamics and Evaluation of Alternative Management Strategies for Nonnative Lake Trout in Priest Lake, Idaho

AbstractLake Trout Salvelinus namaycush have been introduced widely throughout the western USA to enhance recreational fisheries, but high predatory demand can create challenges for management of yield and trophy fisheries alike. Lake Trout were introduced to Priest Lake, Idaho, during the 1920s, but few fishery‐independent data are available to guide current or future management actions. We collected fishery‐independent data to describe population dynamics and evaluate potential management scenarios using an age‐structured population model. Lake Trout in Priest Lake were characterized by fast growth at young ages, which resulted in young age at maturity. However, adult growth rates and body condition were lower than for other Lake Trout populations. High rates of skipped spawning (>50%) were also observed. Model projections indicated that the population was growing (λ = 1.03). Eradication could be achieved by increasing annual mortality to 0.32, approximately twice the current rate. A protected slot length limit could increase population length‐structure, but few fish grew fast enough to exit the slot. In contrast, a juvenile removal scenario targeting age‐2 to age‐5 Lake Trout maintained short‐term harvest of trophy‐length individuals while reducing overall population abundance.

Evaluation of alternative management strategies for maintenance of genetic variation in wildlife populations

Wildlife management strategies are often designed around a population's demographic goals, but such strategies also can inadvertently impact genetic variation. For species like bison Bison bison, where management includes the regular removal of individuals to maintain restricted population sizes on constrained landscapes, management actions can be tailored to address genetic diversity retention in addition to simply maintaining a target population size. In this study, we provide an assessment of alternative culling strategies for maintenance of genetic variation in managed wildlife populations. Our primary goal was to compare the long-term retention of genetic variation and accumulation of inbreeding among three types of culling strategies, including one that considered genetic variation directly by measuring variation at a suite of variable loci [mean allele frequency (MAF) strategy], one that used genome-wide measures of variation [mean kinship (MK) strategy] and one that relied solely on demographic information (sex and age; RANDOM). To achieve this goal, we built an individual-based model, parameterized in accordance with bison biology, to project levels of genetic variation and inbreeding over time under each of the three management strategies. Our results suggest wildlife management strategies that incorporate goals for retaining genetic variation (MAF and MK strategies) are better suited to preserving the evolutionary potential of wildlife populations than those that focus solely on a target size and demographic stability (RANDOM). In particular, the MK culling strategy performed the best at maximizing the retention of genome-wide variation. These results extend previous work demonstrating the utility of pedigree-based mate selection strategies in captive population management, and show that such strategies maximize the retention of genome-wide variation under culling practices as well. These models will aid in the long-term management of bison, and can be adapted to other managed wildlife species.

Interior Least Tern (Sternula antillarum) breeding distribution and ecology: implications for population‐level studies and the evaluation of alternative management strategies on large, regulated rivers

Interior Least Terns (Sternula antillarum) (ILT) are colonial, fish-eating birds that breed within active channels of large sand bed rivers of the Great Plains and in the Lower Mississippi Valley. Multipurpose dams, irrigation structures, and engineered navigation systems have been present on these rivers for many decades. Despite severe alteration of channels and flow regimes, regulation era floods have remained effective at maintaining bare sandbar nesting habitat on many river segments and ILT populations have been stable or expanding since they were listed as endangered in 1985. We used ILT breeding colony locations from 2002 to 2012 and dispersal information to identify 16 populations and 48 subpopulations. More than 90% of ILT and >83% of river km with suitable nesting habitat occur within the two largest populations. However, replicate populations remain throughout the entire historical, geophysical, and ecological range of ILT. Rapid colonization of anthropogenic habitats in areas that were not historically occupied suggests metapopulation dynamics. The highest likelihood of demographic connectivity among ILT populations occurs across the Southern Plains and the Lower Mississippi River, which may be demographically connected with Least Tern populations on the Gulf Coast. Paired ecological and bird population models are needed to test whether previously articulated threats limit ILT population growth and to determine if management intervention is necessary and where. Given current knowledge, the largest sources of model uncertainty will be: (1) uncertainty in relationships between high flow events and subsequent sandbar characteristics and (2) uncertainty regarding the frequency of dispersal among population subunits. We recommend research strategies to reduce these uncertainties.

Evaluation of FAD-associated purse seine fishery reduction strategies for bigeye tuna (Thunnus obesus) in the Indian Ocean

In the Indian Ocean, bigeye tuna supports one of the most important fisheries in the world. This fishery mainly consists of two components: longline and purse seine fisheries. Evidence of overfishing and stock depletion of bigeye tuna calls for an evaluation of alternative management strategies. Using an age-structured operating model, parameterized with the results derived in a recent stock assessment, we evaluated the effectiveness of applying constant fishing mortality (CF) and quasi-constant fishing mortality (QCF) strategies to reduce fishing effort of purse seining with fish aggregating devices (FADs) at different rates. Three different levels of productivity accounted for the uncertainty in our understanding of stock productivity. The study shows that the results of CF and QCF are similar. Average SSB and catch during simulation years would be higher if fishing mortality of FAD-associated purse seining was reduced rapidly. The banning or rapid reduction of purse seining with FAD resulted in a mean catch, and catch in the last simulation year, higher than that of the base case in which no change was made to the purse seine fishery. This could be caused by growth overfishing by purse seine fisheries with FADs according to the per-recruit analysis. These differences would be more obvious when stock productivity was low. Transferring efforts of FAD-associated purse seining to longline fisheries is also not feasible. Our study suggests that changes are necessary to improve the performance of the current management strategy.

Empirical analysis and transboundary management for Georges Bank multispecies fishery

This paper reports the results of a bioeconomic evaluation of alternative management strategies for the Georges Bank transboundary multispecies fishery. Because the distribution of the principal groundfish resources on Georges Bank involves substantial movement and migration across the US–Canada boundary, the harvest by one country affects the benefits to the other country. An empirically based model of the transboundary multispecies fishery was built to simulate alternative management strategies imposed by each country. The simulations were used to help determine whether the status quo management is superior to any other strategy and, if not, what other strategies are better in terms of economic performance. Our aim is to determine whether there are combinations of US and Canadian harvest policies that would make both countries better off and whether a “win–win” strategy exists in the fishery. The results suggest that there are win–win strategies in terms of economic benefits, but such strategies may not be legally feasible under current fisheries law.

CATCH: decision support for stakeholders in catchment areas

Policy proposals for the management of water resources need to take into account two emerging themes: public involvement in the development of resource use policy and water management on a catchment level. The CATCH-model, a decision support system for catchment-based water management, builds on the use of ‘discourse and deliberation’ within stakeholder groups to define relevant socio-economic parameters and the relationships between these parameters. The sets of matrices that describe these parameters and their interrelation serve as the basis for evaluation of alternative management strategies and evaluation of specific measures for improving water quality.

Simulating the Impact of Management Practices on Nitrous Oxide Emissions

AbstractEffective evaluation of alternative management strategies to control global warming requires tools for simulating emissions of N2O from soils across a range of soil properties, weather, and management inputs. We hypothesized that with modification to the nitrification and denitrification submodels of the Nitrate Leaching and Economic Analysis Package (NLEAP) model, we could simulate daily N2O emissions as a function of soil moisture, temperature, N content, and other factors. Field parameterization was conducted on an Ulm clay loam soil (a fine, montmorillonitic, mesic Ustollic Haplargid) and validation experiments for N2O gas emissions were performed on an on‐farm swine effluent study site on a Valent sandy soil (a mixed, mesic Ustic Torripsamment). The unitless model parameters reflecting the maximum fraction of selected N transformations emitted as N2O for nitrification (αN), wet‐period denitrification (αw), and dry‐period denitrifiation (αd) were calibrated as 0.065, 0.050, and 0.520 separately and then used in the validation study. The trends and magnitudes of simulated N2O emissions were statistically consistent with the results obtained from the field experiments (r = 0.78). Experimental results showed that the decline of N2O emission rates from 70 to 2 g N ha−1 d−1 during the growing season was related to soil N content decline from 33 to 4 mg kg−1. Simulated effects of field management on annual N2O emissions indicated that plowing decreased N2O relative to notillage corn (Zea mays L.), irrigation increased N2O 14% relative to dry‐land corn, and doubling fertilization N rates from 100 to 200 kg ha−1 increased N2O emissions 60%.

IMAGES: An integrated model of an arid grazing ecological system

A conceptual model of the pastoral production system within the arid, winter rainfall shrublands of Western Australia is described. The building blocks of this model are pasture-type models which are considered to represent the major productive resource within individual paddocks. A generalised model of such an arid-zone pasture type is described which incorporates the major components of the soil-plant-animal system, and which treats explicitly the effect of herbivores on the condition of the resource. The model has been parameterised for five pasture types based on data from long term exclosures, grazing trials and rangeland monitoring programmes in Western Australia. Validation of the pasture-type models against a range of hypothetical scenarios has produced results generally in agreement with expectations, suggesting that the models have utility for the evaluation of alternative management strategies and identification of key ecological proceses or research priorities. Future development of the pasture-type models is discussed, in particular the development of a whole property model which would facilitate research into holistic management strategies and the contribution that pasture-type models may make to the development of decision support systems for rangeland management.