Management Reference Points Research Articles

An alternative reference point in the context of ecosystem-based fisheries management: maximum sustainable dead biomass

Abstract Under the 2013 Reform of the European Union's Common Fisheries Policy (CFP), fisheries management aims to ensure that, within a reasonable time frame, the exploitation of marine biological resources restores and maintains populations of harvested stocks above levels that can produce the maximum sustainable yield (MSY). The CFP also calls for the implementation of an ecosystem-based approach to fisheries management (EBFM). In this paper, we present the concept of maximum sustainable dead biomass (MSDB) and its associated management reference points for fishing mortality and spawning-stock biomass as alternatives to those associated with MSY. The concept of MSDB is illustrated by a dynamic pool production model of a virtual fish stock which takes into account variations in natural mortality (M), fishing mortality (F), and exploitation pattern. Our approach implies a compensatory mechanism whereby survivors may benefit from compensatory density dependence and is implemented through progressive substitution of M with F for varying rates of total mortality (Z). We demonstrate that the reference points for fishing mortality and spawning-stock biomass associated with MSDB are less sensitive to increasing compensation of M with F than those associated with MSY and more sensitive to changes in selection pattern. MSDB-based reference points, which are consistent with maximum stock productivity, are also associated with lower fishing mortality rates and higher stock biomasses than their MSY-based counterparts. Given that selection pattern can be influenced through fishery input measures (e.g. technical gear measures, decisions on areas, and/or times of fishing), whereas variations of M in response to F are not controllable (indeed poorly understood), that the results of many fish stock assessments are imprecise, that maximum stock productivity corresponds to MSDB and that MSY-based reference points may best be considered as limits, we propose that MSDB-based reference points provide a more appropriate basis for management under an EBFM.

Maternal age effects on Atlantic cod recruitment and implications for future population trajectories

Abstract Exploited fish populations frequently exhibit truncated age-structure. To address a basic question in fisheries science and conservation biology—how does age truncation affect population dynamics and productivity?—we explored the effect of age-structure on recruitment dynamics of ten stocks of Atlantic cod (Gadus morhua). Based on six alternative stock–recruitment relationships, we compared models that included and excluded maternal age-structure effects on recruitment. In all ten stocks, a recruitment model that included a maternal age-dependent effect was preferred over the standard Ricker model and in seven of the ten stocks, the preferred statistical model included a positive effect of either maternal age or mass on recruitment. Simulations comparing standard and maternal age dependent recruitment two decades into the future suggest that the inclusion of maternal age in recruitment models has little effect on projected biomasses. However, this similarity in biomass trajectory masked an increased sensitivity of populations with maternal age-dependent recruitment to stock age-structure. In particular, simulations with maternal age-dependent recruitment responded strongly to changes in fishing mortality on the oldest age classes, while simulations using standard recruitment models did not. Populations with maternal age-dependent recruitment can exhibit increased biomass catch even if fishing mortality on older individuals was reduced. Overall, simulations suggested that the influence of maternal age on population dynamics are more nuanced than suggested by previous research and indicate that careful consideration of the effects of age-structure on populations may lead to substantially different fisheries management reference points—particularly with respect to age-specific fishing mortality—than classical models. While these results suggest a link between maternal age and population productivity, future research requires the incorporation of biologically reasonable and empirically defensible mechanisms to clarify the effect of age on population dynamics.

The potential for spatial distribution indices to signal thresholds in marine fish biomass.

The frequently observed positive relationship between fish population abundance and spatial distribution suggests that changes in distribution can be indicative of trends in abundance. If contractions in spatial distribution precede declines in spawning stock biomass (SSB), spatial distribution reference points could complement the SSB reference points that are commonly used in marine conservation biology and fisheries management. When relevant spatial distribution information is integrated into fisheries management and recovery plans, risks and uncertainties associated with a plan based solely on the SSB criterion would be reduced. To assess the added value of spatial distribution data, we examine the relationship between SSB and four metrics of spatial distribution intended to reflect changes in population range, concentration, and density for 10 demersal populations (9 species) inhabiting the Scotian Shelf, Northwest Atlantic. Our primary purpose is to assess their potential to serve as indices of SSB, using fisheries independent survey data. We find that metrics of density offer the best correlate of spawner biomass. A decline in the frequency of encountering high density areas is associated with, and in a few cases preceded by, rapid declines in SSB in 6 of 10 populations. Density-based indices have considerable potential to serve both as an indicator of SSB and as spatially based reference points in fisheries management.

Evaluation and management implications of uncertainty in a multispecies size-structured model of population and community responses to fishing.

Implementation of an ecosystem approach to fisheries requires advice on trade-offs among fished species and between fisheries yields and biodiversity or food web properties. However, the lack of explicit representation, analysis and consideration of uncertainty in most multispecies models has limited their application in analyses that could support management advice.We assessed the consequences of parameter uncertainty by developing 78 125 multispecies size-structured fish community models, with all combinations of parameters drawn from ranges that spanned parameter values estimated from data and literature. This unfiltered ensemble was reduced to 188 plausible models, the filtered ensemble (FE), by screening outputs against fish abundance data and ecological principles such as requiring species' persistence.Effects of parameter uncertainty on estimates of single-species management reference points for fishing mortality (FMSY, fishing mortality rate providing MSY, the maximum sustainable yield) and biomass (BMSY, biomass at MSY) were evaluated by calculating probability distributions of estimated reference points with the FE. There was a 50% probability that multispecies FMSY could be estimated to within ±25% of its actual value, and a 50% probability that BMSY could be estimated to within ±40% of its actual value.Signal-to-noise ratio was assessed for four community indicators when mortality rates were reduced from current rates to FMSY. The slope of the community size spectrum showed the greatest signal-to-noise ratio, indicating that it would be the most responsive indicator to the change in fishing mortality F. Further, the power of an ongoing international monitoring survey to detect predicted responses of size spectrum slope was higher than for other size-based metrics.Synthesis and applications: Application of the ensemble model approach allows explicit representation of parameter uncertainty and supports advice and management by (i) providing uncertainty intervals for management reference points, (ii) estimating working values of reference points that achieve a defined reduction in risk of not breaching the true reference point, (iii) estimating the responsiveness of population, community, food web and biodiversity indicators to changes in F, (iv) assessing the performance of indicators and monitoring programmes and (v) identifying priorities for data collection and changes to model structure to reduce uncertainty.

Revisiting safe biological limits in fisheries

AbstractThe appropriateness of three official fisheries management reference points used in the north‐east Atlantic was investigated: (i) the smallest stock size that is still within safe biological limits (SSBpa), (ii) the maximum sustainable rate of exploitation (Fmsy) and (iii) the age at first capture. As for (i), in 45% of the examined stocks, the official value for SSBpa was below the consensus estimates determined from three different methods. With respect to (ii), the official estimates of Fmsy exceeded natural mortality M in 76% of the stocks, although M is widely regarded as natural upper limit for Fmsy. And regarding (iii), the age at first capture was below the age at maturity in 74% of the stocks. No official estimates of the stock size (SSBmsy) that can produce the maximum sustainable yield (MSY) are available for the north‐east Atlantic. An analysis of stocks from other areas confirmed that twice SSBpa provides a reasonable preliminary estimate. Comparing stock sizes in 2013 against this proxy showed that 88% were below the level that can produce MSY. Also, 52% of the stocks were outside of safe biological limits, and 12% were severely depleted. Fishing mortality in 2013 exceeded natural mortality in 73% of the stocks, including those that were severely depleted. These results point to the urgent need to re‐assess fisheries reference points in the north‐east Atlantic and to implement the regulations of the new European Common Fisheries Policy regarding sustainable fishing pressure, healthy stock sizes and adult age/size at first capture.

Potential effects of large linear pipeline construction on soil and vegetation in ecologically fragile regions.

Long-distance pipeline construction results in marked human disturbance of the regional ecosystem and brings into question the safety of pipeline construction with respect to the environment. Thus, the direct environmental impact and proper handling of such large projects have received much attention. The potential environmental effects, however, have not been fully addressed, particularly for large linear pipeline projects, and the threshold of such effects is unclear. In this study, two typical eco-fragile areas in western China, where large linear construction projects have been conducted, were chosen as the case study areas. Soil quality indices (SQI) and vegetation indices (VI), representing the most important potential effects, were used to analyze the scope of the effect of large pipeline construction on the surrounding environment. These two indices in different buffer zones along the pipeline were compared against the background values. The analysis resulted in three main findings. First, pipeline construction continues to influence the nearby eco-environment even after a 4-year recovery period. During this period, the effect on vegetation due to pipeline construction reaches 300m beyond the working area, and is much larger in distance than the effect on soil, which is mainly confined to within 30m either side of the pipeline, indicating that vegetation is more sensitive than soil to this type of human disturbance. However, the effect may not reach beyond 500m from the pipeline. Second, the scope of the effect in terms of distance on vegetation may also be determined by the frequency of disturbance and the intensity of the pipeline construction. The greater the number of pipelines in an area, the higher the construction intensity and the more frequent the disturbance. Frequent disturbance may expand the effect on vegetation on both sides of the pipeline, but not on soil quality. Third, the construction may eliminate the stable, resident plant community. During the recovery period, the plant community in the work area of the pipeline is replaced by some species that are rare or uncommon in the resident plant community because of human disturbance, thereby increasing the plant diversity in the work area. In terms of plant succession, the duration of the recovery period has a direct effect on the composition and structure of the plant community. The findings provide a theoretical basis and scientific foundation for improving the environmental impact assessment (EIA) of oil and gas pipeline construction as it pertains to the desert steppe ecosystem, and provide a reference point for recovery and management of the eco-environment during the pipeline construction period.

The effect of low-cost country sourcing on supply chain administration cost

While the key advantage of low-cost country (LCC) sourcing is in low prices, other aspects of conducting sourcing from these countries remain problematic. This research quantifies the effect of LCC sourcing on the cost of supply chain administration, and examines the possible role of firm size and industry in this relationship. The research draws on survey data, with respondents from manufacturing firms operating in Finland. The results indicate that the supply chain administration cost among manufacturing firms seems to rise with the increase in LCC sourcing. The results also suggest that companies in technologically intensive industries experience higher costs, whereas firm size does not have an effect on costs. The research contributes to the debate on the cost-related effects of LCC sourcing, by offering quantified results that can be used as the reference point for managers contemplating the pros and cons in increasing the share of LCC sourcing.

Quirky patterns in time-series of estimates of recruitment could be artefacts

Abstract The accessibility of databases of global or regional stock assessment outputs is leading to an increase in meta-analysis of the dynamics of fish stocks. In most of these analyses, each of the time-series is generally assumed to be directly comparable. However, the approach to stock assessment employed, and the associated modelling assumptions, can have an important influence on the characteristics of each time-series. We explore this idea by investigating recruitment time-series with three different recruitment parameterizations: a stock–recruitment model, a random-walk time-series model, and non-parametric “free” estimation of recruitment. We show that the recruitment time-series is sensitive to model assumptions and this can impact reference points in management, the perception of variability in recruitment and thus undermine meta-analyses. The assumption of the direct comparability of recruitment time-series in databases is therefore not consistent across or within species and stocks. Caution is therefore required as perhaps the characteristics of the time-series of stock dynamics may be determined by the model used to generate them, rather than underlying ecological phenomena. This is especially true when information about cohort abundance is noisy or lacking.

Age-specific natural mortality rates in stock assessments: size-based vs. density-dependent

Abstract Natural mortality (M) rates are difficult to measure empirically and are often specified in stock assessments based on life history characteristics. More recently, these specifications have included M as a function of the size or age of a fish. However, natural mortality is a dynamic parameter that will change with the suite of predators and, thus, indirectly with cohort size and age. As an alternative, a density-dependent M rate function is derived and compared with the commonly used Lorenzen model, where M at age forms an allometric relationship with weight-at-age. The density-dependent model expresses M as a function of two parameters: one density dependent and one density independent. Properties of the two models (size-based vs. density-dependent) were explored to indicate conditions where the results are and are not similar. Associated catch equations, equilibrium analyses, and non-linear replacement lines in stock–recruitment theory are examined. Just as with density-independent values of M, most assessment data are not sufficient to provide precise estimates of density-dependent M parameters. However, the density-dependent model provides a basis for incorporating ecological variability into single-species assessments, noting the differing dynamics between short- and long-lived species. The incorporation of dynamic natural mortality has implications when estimating abundance trends and stock status, and ultimately setting management reference points.

The Impact of Career Development on Employee Commitment of Part-Time Faculty (PTF) in Hong Kong’s Continuing Professional Development (CPD) Sector

Aims: The development of knowledge-based economy in Hong Kong requires employees with higher education level and more up-to-date knowledge. Information and communication technology (ICT) industry has been growing rapidly which is important for building a knowledge-based economy by providing higher mobility of information, more efficient communication network and sharing of knowledge between business partners. In 2002 the HKSAR Government has set up a Continuing Education Fund to encourage employees in Hong Kong to improve their education and update their knowledge by enrolling into continuing professional development courses. This policy provides opportunities to courses providers to offer continuing professional development (CPD) courses. Since these CPD courses are provided after work so the courses are conducted by part-time faculty (PTF) and there is a need to recruit part-time staff in delivering these courses. Recruitment of PTF gives course providers the benefit of meeting their teaching needs economically and flexibly but educators have often expressed concern over whether Research Article British Journal of Education, Society & Behavioural Science, 4(1): 52-73, 2014 53 the performance of PTF is in anyway affected by the absence of career development opportunities. Study Design: This study was a quantitative study which used [1] five-component commitment model to examine the effects of the perception of value of career development (VCD) on the commitment components of PTF. Place and Duration of Study: The study was taken in Hong Kong between June 2011 and June 2012. Methodology: Sample data from a population of PTF working at the 450 registered CPD course providers in Hong Kong was collected from an online questionnaire. Finally 270 set of data collated together was analyzed by factor analysis, correlation tests and multiple regression respectively. Results: The results of this study suggest that perceived VCD was affirmed to have a significantly positive influence on employee commitment, while perception of the availability of career development opportunities was found to have a moderating effect on the association between perceived VCD and employee commitment. Conclusion: This study has both theoretical and managerial implications. The examination of the complicated relationship between career development and employee commitment of PTF in Hong Kong’s CPD industry can therefore serve as a useful reference point for both academic researchers and education managers. The findings can also help CPD institutes to formulate suitable human resource strategies for attracting and retaining well-qualified practitioners to become PTF.

334

Introduction: Hypertension is a complex spectrum of diseases with differing morbidities. Defining risk profiles in individuals and selecting and monitoring treatment response relies heavily on epidemiologic studies with uncertain application to the individual. Hypertension continues to be defined without reference to a hemodynamic basis for changes in pressure. If pressure is always the product of cardiac performance and vascular resistance, then it cannot be understood apart from a hemodynamic cause. Methods: Over 52 months, hemodynamic data was collected and graphically analysed in 501(253M,248F) elderly male and female subjects presenting for elective and urgent major surgery. Guyton’s equation relating systemic pressure to cardiac performance was simplified by removal of HR, and the alternative equation used to define cardiac and vascular components of systemic pressure. Using this “Pressure Field method”, hemodynamic data at 20–60 second intervals was collected and graphed for periods from 2 hours to 28 days. All systemic pressure measurements were referenced to a database of subjects of similar age, gender and body surface area. Results: The systemic pressure gradient (MAP-CVP) in older male and female subjects presenting for elective and urgent major surgery was at least 80 mm Hg, and increased after 55 yrs to 110 mm Hg in females and 100 mm Hg in male subjects. Hypertension was present when the age and gender specific gradient exceeded values for age-matched normal subjects. The pathophysiology of hypertension using the Pressure Field method could be subdivided into 5 hemodynamic subgroups, consisting of an increased age and gender specific Systemic Pressure gradient and one of the following: (1) decreased R, increased SV (2) increased SV, constant R (3) increased SV, increased R (4) increased R, constant SV and (5) decreased SV, increased R. The resistance value (R) was defined by the equation “(MAP-CVP)=SV x R”. Conclusions: Diagnosis and therapy of hypertension depends on defining the physiology in each individual and using normal controls as the reference point for pharmacological management of the circulation. The pressure field model differentiates cardiogenic and vasogenic hypertension and mixed patterns and permits individualization of therapy. This contrasts with the current approach which is based on noninvasive measurement of pressure without any hemodynamic measurements.

The politics, science and policy of reference points for resource management

Reference points are specific values related to the state of a resource to which targets and limits for harvest management can be set. Although reference points evolved within fisheries science, they are likely to be widely applicable across a range of ecosystems and environments, as the principles behind their development and implementation apply to any harvested system. This special issue ofEnvironmental Conservationtakes a critical look at the ways in which reference points have been used previously, including the political, scientific and management contexts that have hindered and enabled their implementation. Through these experiences, a range of recommendations are made, highlighting the importance of social context in which biological reference points are developed and in favour of approaches that deal explicitly with uncertainty. When implemented without qualification, reference points have proven effective at preventing fisheries collapse and rebuilding depleted stocks; where they have not, management failures have occurred. Given the social-ecological complexity of fisheries management, the papers in this special issue provide a strong argument for the application of reference points across a range of resource management problems.

Can fisheries-induced evolution shift reference points for fisheries management?

Abstract Heino, M., Baulier, L., Boukal, D. S., Ernande, B., Johnston, F. D., Mollet, F. M., Pardoe, H., Therkildsen, N. O., Uusi-Heikkilä, S., Vainikka, A., Arlinghaus, R., Dankel, D. J., Dunlop, E. S., Eikeset, A. M., Enberg, K., Engelhard G. H., Jørgensen, C., Laugen, A. T., Matsumura, S., Nusslé, S., Urbach, D., Whitlock, R., Rijnsdorp, A. D., and Dieckmann, U. 2013. Can fisheries-induced evolution shift reference points for fisheries management? – ICES Journal of Marine Science, 70: 707–721. Biological reference points are important tools for fisheries management. Reference points are not static, but may change when a population's environment or the population itself changes. Fisheries-induced evolution is one mechanism that can alter population characteristics, leading to “shifting” reference points by modifying the underlying biological processes or by changing the perception of a fishery system. The former causes changes in “true” reference points, whereas the latter is caused by changes in the yardsticks used to quantify a system's status. Unaccounted shifts of either kind imply that reference points gradually lose their intended meaning. This can lead to increased precaution, which is safe, but potentially costly. Shifts can also occur in more perilous directions, such that actual risks are greater than anticipated. Our qualitative analysis suggests that all commonly used reference points are susceptible to shifting through fisheries-induced evolution, including the limit and “precautionary” reference points for spawning-stock biomass, Blim and Bpa, and the target reference point for fishing mortality, F0.1. Our findings call for increased awareness of fisheries-induced changes and highlight the value of always basing reference points on adequately updated information, to capture all changes in the biological processes that drive fish population dynamics.

Distinguishing benchmarks of biological status from management reference points: A case study on Pacific salmon in Canada

SUMMARYFor fisheries with multiple, competing objectives, identifying and applying reference points for management can present difficult trade-offs between long-term biological and shorter-term socioeconomic considerations. The term biological benchmarks is proposed to demarcate zones of population status based on conservation and production considerations. These scientifically derived benchmarks contrast with management reference points that generally require additional shorter-term socioeconomic information best obtained through public consultations. This paper illustrates the distinction between biological benchmarks and management reference points with a case study on Pacific salmon (Oncorhynchusspp.). In Canada, the management and assessment of wild Pacific salmon are guided by a major 2005 conservation policy, which calls for the identification of biological benchmarks to categorize status of demographically isolated populations, and decision-support tools, such as management reference points, to integrate biological information with appropriate social and economic information. In the Fraser River (British Columbia, Canada), the selection of management reference points for sockeye salmon (O. nerka) fisheries explicitly considered trade-offs between the probability of meeting long-term biological objectives on component populations and harvest objectives on population aggregates. Decisions about reference points were made in a consultative process that included extensive stakeholder engagement. Other agencies are urged to distinguish biological benchmarks from management reference points to ensure transparency in the relative influence of biological versus socioeconomic information in decision making.

A perspective on steepness, reference points, and stock assessment

We provide a perspective on steepness, reference points for fishery management, and stock assessment. We first review published data and give new results showing that key reference points are fixed when steepness and other life history parameters are fixed in stock assessments using a Beverton–Holt stock–recruitment relationship. We use both production and age-structured models to explore these patterns. For the production model, we derive explicit relationships for steepness and life history parameters and then for steepness and major reference points. For the age-structured model, we are required to generally use numerical computation, and so we provide an example that complements the analytical results of the production model. We discuss what it means to set steepness equal to 1 and how to construct a prior for steepness. Ways out of the difficult situation raised by fixing steepness and life history parameters include not fixing them, using a more complicated stock–recruitment relationship, and being more explicit about the information content of the data and what that means for policy makers. We discuss the strengths and limitations of each approach.

Evaluating sustainability of fisheries bycatch mortality for marine megafauna: a review of conservation reference points for data-limited populations

SUMMARYFisheries bycatch threatens populations of marine megafauna such as marine mammals, turtles, seabirds, sharks and rays, but fisheries impacts on non-target populations are often difficult to assess due to factors such as data limitation, poorly defined management objectives and lack of quantitative bycatch reduction targets. Limit reference points can be used to address these issues and thereby facilitate adoption and implementation of mitigation efforts. Reference points based on catch data and life history analysis can identify sustainability limits for bycatch with respect to defined population goals even when data are quite limited. This can expedite assessments for large numbers of species and enable prioritization of management actions based on mitigation urgency and efficacy. This paper reviews limit reference point estimators for marine megafauna bycatch, with the aim of highlighting their utility in fisheries management and promoting best practices for use. Different estimators share a common basic structure that can be flexibly applied to different contexts depending on species life history and available data types. Information on demographic vital rates and abundance is required; of these, abundance is the most data-dependent and thus most limiting factor for application. There are different approaches for handling management risk stemming from uncertainty in reference point and bycatch estimates. Risk tolerance can be incorporated explicitly into the reference point estimator itself, or probability distributions may be used to describe uncertainties in bycatch and reference point estimates, and risk tolerance may guide how those are factored into the management process. Either approach requires simulation-based performance testing such as management strategy evaluation to ensure that management objectives can be achieved. Factoring potential sources of bias into such evaluations is critical. This paper reviews the technical, operational, and political challenges to widespread application of reference points for management of marine megafauna bycatch, while emphasizing the importance of developing assessment frameworks that can facilitate sustainable fishing practices.

Life-history reference points for management of an exploited tropical seahorse

The present research provides the first demographic reference points for tropical seahorses, relevant to conservation of this largely tropical genus Hippocampus, which is listed on the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix II. Findings defined the life-history and in situ vital rates of the tiger tail seahorse, H. comes, expanding previous understanding of demographic diversity in reef fishes. We quantified growth, reproduction and survival rates, drawing on mark–recapture intervals from focal observations, underwater visual census and fisheries landings data. The smallest settled individual was 2.7 cm and first benthic cohorts measured 3.0–4.0 cm. Assuming individually variable growth, the mean parameters for the von Bertalanffy growth equation were Linf = 16.7 cm, K = 2.9 year–1 and t0 = 0.03. Physical maturity occurred at 9.3 cm, reproductive activity at 11.6 cm and annual recruitment during the dry, inter-monsoon window from February to May. Size-dependent survivorship ranged from 3.5% to 45.0% year–1 and longevity was ≥2.5 years. In H. comes, characteristics governing population turnover align with opportunistic strategists, whereas reproductive traits align more closely with equilibrium strategists. Non-extractive marine reserves are one management approach that could serve such intermediate strategists, providing refugia for colonisation, while protecting important large, fecund adults.

Integrating Anthropogenic and Climatic Factors in the Assessment of the Caribbean Spiny Lobster (<i>Panulirus argus</i>) in Cuba: Implications for Fishery Management

The Caribbean spiny lobster Panulirus argus , the most valuable Cuban fishery resource, is managed with a set of input and biological controls. The aim of this article was to integrate two indices related water and nutrients supply and tropical cyclones activity in the stock assessment, through internal estimation of the parameters of a spawning stock recruitment function in a statistical catch-at-age analysis. The population dynamics model allowed estimating key Reference Points for management at fixed levels of fishing mortality rate and environmental conditions. The results indicate that the reduction of recruitment and catches in the Cuban spiny lobster fishery could be a result of synergistic cumulative effects because of the anthropogenic reduction of nutrients supplies and the increase of the potential destructiveness of tropical cyclones since 1994, mainly from 2001 on. Although the degradation of the coastal habitat quality in Cuba is apparent and perhaps unavoidable, the assessment of the impact allows implementing management actions for the spiny lobster fishery sustainability. The implementation of annual TAC depending on the stock status, have maintained the fishery around the more conservative Reference Points F 40% and F 0.1 during the current unfavorable environment period.

Construction of biological reference points for management of the Dungeness crab, Cancer magister, fishery in the Fraser River Delta, British Columbia, Canada

The objective of this study was to define two biological reference points, the Upper Stock Reference Point (USR) and the Limit Reference Point (LRP), to facilitate management of the Fraser River delta commercial Dungeness crab (Cancer magister) fishery in a precautionary manner. The USR is the stock level below which the removal rate is progressively reduced to avoid reaching the LRP. The LRP is the stock level below which productivity is sufficiently impaired to cause serious harm. Currently, the commercial Dungeness crab fishery in the Fraser River delta is managed with a minimum size limit (165mm carapace width point-to-point), non-retention of females and soft-shell crabs, and a restricted fishing season (June to November) to protect large males during the winter/spring moult period. We evaluated variations in legal male, sublegal male, and female Dungeness crab abundances using fishery-independent trap surveys from 1988 to 2010. We also examined proportions of soft-shell legal male and female crabs using survey data and information collected from commercial fishing. A relationship existed between female abundance and corresponding legal male abundance five years later, which is well described by the Beverton–Holt stock–recruitment model. We conducted simulations to assess possible adverse impacts of fishing on the crab population. We assumed the population would stabilize at the existing abundance upon suspension of commercial harvesting if abundance has been steadily declining. Using the stock–recruitment relationship along with information on commercial catch compositions and soft-shell proportions, we assessed the potential reduction in legal male and female crab abundances, given persistent fishing, before the population reaches a lower equilibrium. The amount of reduction to legal male and female crabs increases with decreasing population size. If legal male crab abundance is 50% and 20% of maximum possible recruitment, then fishing would reduce female abundance by 20% and 48%, respectively, before the population is stabilized. We propose these two female abundance levels as the USR and LRP for managing the Fraser River commercial Dungeness crab fishery.

Public Authorities for Entrepreneurship: A management approach to execute competitiveness policies

Decentralization, globalization and European Union cohesion and competitiveness agendas have shifted the focus of development policies from the central to the regional and local levels. Most studies on economic development are informed by macroeconomic and entrepreneurial theories, the normative implications of which are unclear for public authorities attempting to enhance competitiveness and entrepreneurship in their communities. This paper discusses the centrality of implementation efforts for the effectiveness of regional and local competitiveness programmes and policies. Striving to capture the challenges posed by the international literature, the paper presents a managerial approach, developed under an inductive–deductive method grounded in some Italian cases of entrepreneurial development. The intention is to provide a reference point for regional and local public managers whose task it is to select and execute actions and instruments to support businesses' start up and growth.