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1.
The lecture traces the historical path to overfishing of the world's fish and shellfish stocks, and provides an assessment of marine fish resources in the later half of the 1990s. The basis of overfishing as noted by various fishery scientists is reviewed. Four factors, including institutional paralysis, the rapidity of technological developments, uncertainty of science, and the inability to monitor and enforce regulations are identified as the major problems leading to overfishing. The failure of the world community to deal with extensive overfishing, appears to have motivated managers and scientists to promote a new fishery management paradigm that focuses on a broader set of problems resulting from fishing, and establishes a more conservative decision‐making process founded on precautionary principle and uncertainty. The author feels that the evolving paradigm will result in the rebuilding of a number of stocks in the United States, but is less certain of its adoption on a global scale, and whether or not science will play a more useful role in fisheries management. It is noted that the support for fisheries science and the status of fisheries have followed opposite courses. Over the past half century marine science has boomed, diversified and become intellectually and materially enriched, while the number of overfished stocks and ecological disasters has increased. Looking ahead it is expected that fisheries management will move into a more conservative era. The focus of fisheries has moved from full use of ocean resources to establishing yields that take into account the impacts of fisheries on target and non‐target species and the ecosystem in general. Although there has been wide‐spread abuse in the use of the world's fishery resources and condemnation of the fishing industries, the author feels that the government institutions must bear the primary responsibility for the historical course of fishery management and its failure.  相似文献   

2.
以有限数据评估方法为基础的海州湾渔业管理策略评估   总被引:1,自引:0,他引:1  
孙铭  张崇良  李韵洲  徐宾铎  薛莹  任一平 《水产学报》2018,42(10):1661-1669
实验以计算机模拟的管理策略评价方法为基础,以海州湾海域的银鲳、小黄鱼、大泷六线鱼和长蛇鲻为例,对基于数据有限方法的管理策略进行了分析评价。模拟结果显示,基于体长的管理策略能够在产量和避免过度捕捞间取得较好的权衡,其管理效果优于基于捕捞努力量的管理策略。模拟结果显示,银鲳和大泷六线鱼处于过渡捕捞状态;小黄鱼种群规模具有较大波动和不确定性;长蛇鲻种群未遭受过度捕捞。研究表明,基于有限数据评估方法的管理策略可以有效避免潜在的过度捕捞,提升遭受过度捕捞群体的产卵群体生物量规模,具有较好的可持续性,并能维持可观的产量,在我国具有广泛的运用前景。  相似文献   

3.
Recruitment overfishing occurs when stocks are fished to a level where recruitment declines proportionally with adult abundance. Although typically considered a commercial fishery problem, recruitment overfishing can also occur in freshwater recreational fisheries. This study developed an age‐structured model to determine if minimum‐length limits can prevent recruitment overfishing in black crappie, Pomoxis nigromaculatus (LeSueur), and walleye, Sander vitreus (Mitchill) fisheries considering angling effort response to changes in fish abundance. Simulations showed that minimum‐length limits prevented recruitment overfishing of black crappie and walleye, but larger minimum‐length limits were required if angler effort showed only weak responses to changes in fish abundance. Low angler‐effort responsiveness caused fishing mortality rates to remain high when stock abundance declined. By contrast, at high effort responsiveness, anglers left the fishery in response to stock declines and allowed stocks to recover. Angler effort for black crappie and walleye fisheries suggested that angler effort could be highly responsive for some fisheries and relatively stable for others, thereby increasing the risk of recruitment overfishing in real fisheries. Recruitment overfishing should be considered seriously in freshwater recreational fisheries, and more studies are needed to evaluate the responsiveness of angler effort to changes in fish abundance.  相似文献   

4.
The exploitation status of white croaker Micropogonias furnieri in southern Brazil is assessed using a production model constructed according to three hypotheses of stock discreetness: an isolated stock in southern Brazil; a straddling stock shared between Brazil and Uruguay; and a straddling stock shared among Brazil, Uruguay and Argentina. Estimates of virgin stock size and maximum sustainable yield were more sensitive to the hypothesis assumed correct, the posterior means varying respectively from 177,648 to 1,007,256 tonnes and from 7459 to 38,677 tonnes. Estimates of stock status in relation to management reference points were more robust to the uncertainties in stock discreetness and indicate that the species in currently overfished (biomass at 60% of Bmsy) and under heavy overfishing (F between approximately 2 and 6 times higher than Fmsy). Results suggest that the relative stability of catches in the region occurs at the expense of a steady decline in stock abundance and that concerted management actions by the three countries are needed to bring the stock to safer levels of exploitation.  相似文献   

5.
Fishery management frequently involves precautionary buffering for scientific uncertainty. For example, a precautionary buffer that scales with scientific uncertainty is used to calculate the acceptable biological catch downward from the overfishing limit in the US federal fishery management system. However, there is little empirical guidance to suggest how large buffers for scientific uncertainty should be. One important component of uncertainty is variation among different assessments of the same stock in estimates of management-relevant quantities. We analysed commercially exploited marine fish and invertebrate stocks around the world and developed Bayesian hierarchical models to quantify inter-assessment variation in terminal year biomass and fishing mortality estimates, reference points, relative biomass and fishing mortality estimates, and overfishing limits. There was little evidence of inter-assessment bias; stock assessment estimates in the terminal year of the assessment were not consistently higher or lower than estimates of the same quantities in future years. However, there was a tendency for extreme values from the terminal year to be pulled closer to the mean in future years. Inter-assessment variation in all estimates differed across regions, and a longer inter-assessment interval generally resulted in greater variation. Inter-assessment uncertainty was greatest for estimates of the overfishing limit, with coefficients of variation ranging from 17% in Europe (non-EU) to 107% for Pacific Ocean pelagic stocks. Because inter-assessment variation is only one component of scientific uncertainty, we suggest that these uncertainty estimates may provide a basis for determining the minimum size of precautionary buffers.  相似文献   

6.
Understanding the impacts of recreational fishing on commercially fished stocks is becoming increasingly relevant for fisheries managers. However, data from recreational fisheries are not commonly included in stock assessments of commercially fished stocks. Simulation models of two assessment methods employed in Australia's Commonwealth fisheries were used to explore how recreational fishery data can be included, and the likely consequences for management. In a data‐poor management strategy for blue eye trevalla, Hyperoglyphe antarctica (Carmichael), temporal trends in recreational catch most affected management outcomes. In a data‐rich age‐structured stock assessment for striped marlin, Kajikia audax (Philippi), estimates of stock status were biased when recreational catches were large or when the recreational fishery targeted different size classes than the commercial fishery and these data were not integrated into the assessment. Including data from recreational fishing can change perceptions of stock status and impact recommendations for harvest strategies and management action. An understanding of recreational fishery dynamics should be prioritised for some species.  相似文献   

7.
Coral reefs support numerous ornamental fisheries, but there are concerns about stock sustainability due to the volume of animals caught. Such impacts are difficult to quantify and manage because fishery data are often lacking. Here, we suggest a framework that integrates several data‐poor assessment and management methods in order to provide management guidance for fisheries that differ widely in the kinds and amounts of data available. First, a resource manager could assess the status of the ecosystem (using quantitative metrics where data are available and semi‐quantitative risk assessment where they are not) and determine whether overall fishing mortality should be reduced. Next, productivity susceptibility analysis can be used to estimate vulnerability to fishing using basic information on life history and the nature of the fishery. Information on the relative degree of exploitation (e.g. export data or ratios of fish density inside and outside no‐take marine reserves) is then combined with the vulnerability ranks to prioritize species for precautionary management and further analysis. For example, species that are both highly exploited and vulnerable are good candidates for precautionary reductions in allowable capture. Species that appear to be less vulnerable could be managed on a stock‐specific basis to prevent over‐exploitation of some species resulting from the use of aggregate catch limits. The framework could be applied to coral reef ornamental fisheries which typically lack landings, catch‐per‐unit‐effort and age‐size data to generate management guidance to reduce overfishing risk. We illustrate the application of this framework to an ornamental fishery in Indonesia.  相似文献   

8.
传统的渔业资源评估方法需以翔实的调查和渔业数据为基础,而现有的大多数种类面临着着渔获量、基础生物学、有效捕捞努力量等数据缺失问题,因此并不适合采用数据需求较高的模型进行评估和管理。面临着渔业资源衰退的严峻形势和渔获量限额管理的迫切要求,基于有限数据的评估方法和渔获量相关的管理方案正被越来越多的国家采用。本研究以东海小黄鱼(Larimichthys polyactis)种群为例,根据渔获量、自然死亡、消减率、生物学参数、开捕体长等数据,采用54种有限数据评估方法,模拟3种捕捞动态,对小黄鱼进行管理策略评价和资源评估。结果显示,以相对产量(relative yield, RY)不低于50%、过度捕捞概率(probability of overfishing, POF)小于50%,生物量低于最大可持续生物量的10%(B0.1B_(MSY))的概率小于20%为风险控制水平,捕捞强度随机波动和增长情景下,分别有6个管理方案(management procedures, MPs)满足既定管理目标;"一般型"和"增长型"捕捞强度情景下, 14个MPs满足管理目标。权衡分析3种捕捞动态下的MPs, 50%FMSY基准法(FMSYref50)可作为小黄鱼渔业最佳的管理方案,POF介于5.46%~6.70%, B0.5B_(MSY)概率介于15.66%~22.73%,长期获得的相对产量介于52%~100%;然而, FMSYref50确定的可接受生物学渔获量(acceptable biological catch, ABC)仅有1.08×10~4 t,与当前产量相差较大。因此,考虑到降低捕捞强度为渔业管控的发展趋势,建议采用动态F比值法(DynF)为小黄鱼渔业管理方案,"下降型"捕捞强度情景下,POF为37.84%, B0.5B_(MSY)概率为38.63%,长期获得的相对产量为84%, ABC为4.03×10~4 t。根据敏感性分析,发现DynF评估的ABC对捕捞产量、资源丰度指数不敏感,而对自然死亡系数、最大可持续捕捞死亡系数与自然死亡系数比值(FMSY_M)和当前资源量均较为敏感,参数值增加会导致ABC增加,表明在开展渔业资源评估时需要着重提高这3种参数的准确性。  相似文献   

9.
Wasted fishery resources: discarded by-catch in the USA   总被引:1,自引:0,他引:1  
Fishery by‐catch, especially discarded by‐catch, is a serious problem in the world's oceans. Not only are the stocks of discarded species affected, but entire trophic webs and habitats may be disrupted at the ecosystem level. This paper reviews discarding in the marine fisheries of the USA; however, the type, diversity and regulatory mechanisms of the fisheries are similar to developed fisheries and management programmes throughout the world. We have compiled current estimates of discarded by‐catch for each major marine fishery in the USA using estimates from existing literature, both published and unpublished. We did not re‐estimate discards or discard rates from raw data, nor did we include data on protected species (turtles, mammals and birds) and so this study covers discarded by‐catch of finfish and fishable invertebrates. For some fisheries, additional calculations were required to transform number data into weight data, and typically length and weight composition data were used. Specific data for each fishery are referenced in Harrington et al. (Wasted Resources: Bycatch and discards in US Fisheries, Oceana, Washington, DC, 2005). Overall, our compiled estimates are that 1.06 million tonnes of fish were discarded and 3.7 million tonnes of fish were landed in USA marine fisheries in 2002. This amounts to a nationwide discard to landings ratio of 0.28, amongst the highest in the world. Regionally, the southeast had the largest discard to landings ratio (0.59), followed closely by the highly migratory species fisheries (0.52) and the northeast fisheries (0.49). The Alaskan and west coast fisheries had the lowest ratios (0.12 and 0.15 respectively). Shrimp fisheries in the southeast were the major contributors to the high discard rate in that region, with discard ratios of 4.56 (Gulf of Mexico) and 2.95 (South Atlantic). By‐catch and discarding is a major component of the impact of fisheries on marine ecosystems. There have been substantial efforts to reduce by‐catch in some fisheries, but broadly based programmes covering all fisheries are needed within the USA and around the world. In response to international agreements to improve fishery management, by‐catch and discard reduction must become a regular part of fishery management planning.  相似文献   

10.
Meta‐analyses of stock assessments can provide novel insight into marine population dynamics and the status of fished species, but the world’s main stock assessment database (the Myers Stock‐Recruitment Database) is now outdated. To facilitate new analyses, we developed a new database, the RAM Legacy Stock Assessment Database, for commercially exploited marine fishes and invertebrates. Time series of total biomass, spawner biomass, recruits, fishing mortality and catch/landings form the core of the database. Assessments were assembled from 21 national and international management agencies for a total of 331 stocks (295 fish stocks representing 46 families and 36 invertebrate stocks representing 12 families), including nine of the world’s 10 largest fisheries. Stock assessments were available from 27 large marine ecosystems, the Caspian Sea and four High Seas regions, and include the Atlantic, Pacific, Indian, Arctic and Antarctic Oceans. Most assessments came from the USA, Europe, Canada, New Zealand and Australia. Assessed marine stocks represent a small proportion of harvested fish taxa (16%), and an even smaller proportion of marine fish biodiversity (1%), but provide high‐quality data for intensively studied stocks. The database provides new insight into the status of exploited populations: 58% of stocks with reference points (n = 214) were estimated to be below the biomass resulting in maximum sustainable yield (BMSY) and 30% had exploitation levels above the exploitation rate resulting in maximum sustainable yield (UMSY). We anticipate that the database will facilitate new research in population dynamics and fishery management, and we encourage further data contributions from stock assessment scientists.  相似文献   

11.
Many of the world’s fish stocks are depleted as a result of overexploitation, pollution and habitat loss. The 2002 World Summit on Sustainable Development (WSSD) sets a target for fisheries to maintain or restore stocks to levels that can produce the maximum sustainable yield (MSY) by 2015. We assessed the global stock status and found that 68% were at or above the MSY level in 2008 and that the 2015 target is unlikely to be met. We compiled data for eight indicators to evaluate the sustainability of fisheries and the gap to meet the WSSD target. These indicators show that the overall condition of global fisheries is declining, long‐term benefits are being compromised, and pressures on fisheries are increasing despite fisheries policy and management actions being taken by coastal States. We develop a bio‐economic model to estimate the costs and benefits of restoring overfished stocks. Our results show that the global fishing capacity needs to be cut by 36–43% from the 2008 level, resulting in the loss of employment of 12–15 million fishers and costing US$96–358 billion for buybacks. On the other hand, meeting the WSSD goal will increase annual fishery production by 16.5 million tonnes, annual rent by US$32 billion and improve biodiversity and functioning of marine ecosystems. However, progress towards rebuilding has been hindered by an unwillingness or inability to accept the short‐term socio‐economic consequences associated with rebuilding fisheries. Thus, there is a pressing need for integration of rebuilding plans into national political and economic decision‐making.  相似文献   

12.
广阔的南海热带海域拥有得天独厚的岛礁资源与环境优势,具有巨大的开发利用潜力。近年来,在国家"海洋强国"战略的提出与稳步践行的背景之下,加快南海岛礁渔业资源的保护与可持续利用已迫在眉睫。现代海洋牧场是集生境修复、资源养护、休闲渔业和景观生态于一体的渔业生产新业态,真正实现了海洋经济发展和海洋生态环境保护并重,但目前南海热带岛礁海洋牧场建设仍严重滞后。充分利用南海热带岛礁海域的资源与环境优势,发展热带海洋牧场可以有力振兴岛礁经济、保护与合理开发岛礁资源,同时也是维护南海海洋权益、实践"海洋强国"战略的有力举措。本文论述了南海热带岛礁海域开展海洋牧场建设的优势,包括政策优势、自然地理优势、资源优势和产业经济优势等;提出南海热带岛礁海洋牧场的适宜建设模式,主要包括资源养护与增殖型海洋牧场和休闲旅游型海洋牧场;综述了广东、广西和海南省在热带近岸和岛礁海洋牧场建设方面的进展;阐述了热带岛礁牧场建设面临的困难和风险,包括气候与自然灾害、生物敌害、基础设施落后、海域使用权审批严格等问题;基于对问题的分析,提出了相关的对策与建议,包括科学选址、优化设施设计与投放方案、研发敌害应对技术、提升自动化信息化运营管理能力、创新牧场投资与运行模式、加大政府政策支持与扶持力度等,相关建议以期为未来南海热带岛礁海洋牧场建设提供策略支持。  相似文献   

13.
为研究野生与养殖大黄鱼(Larimichthys crocea)群体的遗传多样性,对大黄鱼8个野生群体及6个养殖群体共336个样本的线粒体COⅠ基因部分序列进行了扩增和测序分析。实验最终获得序列片段长621 bp,总变异位点38个,简约信息位点23个,单变异位点15个,其中野生群体包含38个变异位点,占总变异的100%,养殖群体包含8个变异位点,占总变异的21.05%。在所有样本中共检测出单倍型34个,单倍型多样性为0.587,核苷酸多样性为0.00194,野生及养殖群体单倍型多样性指数分别为0.714~0.952、0.000~0.581。大黄鱼养殖与野生两个组群间的遗传分化指数为0.04982,占总变异的4.98%,差异极显著(P0.01),组群间群体间的变异占1.46%(P0.05),群体内的变异占93.56%(P0.01)。以上结果表明,大黄鱼的遗传变异主要来自于群体内,养殖群体的遗传多样性显著低于野生群体,两者的遗传多样性程度均处于较低水平,养殖群体间或野生群体间不存在显著的遗传分化,而养殖与野生两大组群间存在着显著的遗传分化。此外,通过对群体遗传结构及进化树的分析表明,东、黄海大黄鱼应属于同一地理种群,但两者间存在较低程度的遗传分化现象,黄海的大黄鱼群体遗传多样性高于东海群体。本研究可为大黄鱼种质资源的保护和恢复提供理论依据。  相似文献   

14.
Individual quota (IQ) management systems in commercial marine fisheries are highly diverse, differing in the security, durability and exclusivity of the harvesting privilege and the transferability of quota units. This diversity in the degree of harvest rights may influence the effectiveness of IQ fisheries to meet management objectives. We conducted a global meta‐analysis of 167 stocks managed under IQs to test whether the strength of harvest rights impacts the conservation status of stocks in terms of catch, exploitation rate and biomass relative to management targets. We used non‐parametric methods to assess non‐linear relationships and linear regression models to explicitly consider interactions among predictors. Most IQ fisheries consistently met fleet‐wide quota limits (94% of stocks had recent catches below or within 10% of quotas), but only 2/3 of IQ fisheries adhered to sustainable management targets for biomass and exploitation rate (68% of stocks had exploitation rates below or within 10% of targets and 63% of stocks had biomass above or within 10% of biomass targets). Strikingly, when exclusivity of the harvesting privilege was low, exploitation rates depended on whether IQ implementation was industry‐driven (exploitation below targets) or government‐mandated (exploitation above targets). At high levels of exclusivity, exploitation rates converged to just below management targets. Transferability of quota units was associated with stock biomass closer to and slightly above target levels than stocks with non‐transferable quota. However, regional differences had the strongest effect on biomass, suggesting that other management or biological attributes of regional fishery systems have greater influence on marine populations.  相似文献   

15.
Tropical hilsa shad, which is an anadromous fish migrating from the sea to spawn in freshwater river, constitutes an important fishery in some Asian and Middle East countries, particularly in Bangladesh. But, historical information on hilsa biology and ecology has confronted the scientists and policymakers with research and management challenges. We have reviewed both the old and recent findings on hilsa fishery to document the status of knowledge and potential gaps, necessary to comprehend for formulating a more effective fishery management plan. Thus, there has been a decline in hilsa catches in the riverine system associated with shift in fish migration routes, indiscriminate harvesting of brood and juvenile fish, and degradation of habitat. Specifically, the riverine hilsa catches peaked in the 1960s, declining thereafter, and became relatively abundant in marine waters since 1990s. Biological data indicated that hilsa goes through multiple reproductive cycles; therefore, a comprehensive understanding of reproductive biology, recruitment by various cohorts, stock abundance and habitats across the life cycle are necessary to accurately impose fishery regulatory measures, such as fishing ban in spawning season in Bangladesh. Moreover, domestication initiative is important for artificial seed production and mariculture development of hilsa that can not only offer economic return to small‐scale farmers but also reduce the growing pressure on capture fishery. Importantly, the arrangement of co‐management is found ideal as fishermen, scientists and managers can work jointly to improve the regulatory processes and to sustain the hilsa fishery over time.  相似文献   

16.
The recent reform of the Common Fisheries Policy (CFP) in Europe highlights the need for improvements in both species and size selectivity. Regarding size selectivity, shifting selectivity towards older/larger fish avoids both growth and recruitment overfishing and reduces unwanted catches. However, the benefits to fish stocks and fishery yields from increasing age/size‐at‐selection are still being challenged and the relative importance of selectivity compared to that of exploitation rate remains unclear. Consequently, exploitation rate regulations continue to dominate management. Here, an age‐structured population model parameterized for a wide range of stocks is used to investigate the effects of selectivity on spawning stock biomass (SSB) and yield. The generic effect of selectivity on SSB and yield over a wide range of stocks is compared to the respective relative effects of exploitation rate and several biological parameters. We show that yield is mainly driven by biological parameters, while SSB is mostly affected by the exploitation regime (i.e. exploitation rate and selectivity). Our analysis highlights the importance of selectivity for fisheries sustainability. Catching fish a year or more after they mature combined with an intermediate exploitation rate (F ≈ 0.3) promotes high sustainable yields at low levels of stock depletion. Examination of the empirical exploitation regimes of 31 NE Atlantic stocks illustrates the unfulfilled potential of most stocks for higher sustainable yields due to high juvenile selection, thus underscoring the importance of protecting juveniles. Explicitly incorporating selectivity scenarios in fisheries advice would allow the identification of optimal exploitation regimes and benefit results‐based management.  相似文献   

17.
The fishery for Argopecten purpuratus in northern Chile, whichcollapsed because of overfishing, has been replaced by aquaculture of thespecies. In 1998, cultures produced 16,474 t, while the highest landings recorded inthe entire history of the fishery was in 1984 (one year after the 1983 ElNiño) with 5275 t. The figures for stock size of the species in the pastand at present, show that the wild stock of scallops today represents notmore than 10–15% of the total stock of the species within Chile, with mostof the individuals being kept in sea farms. Thus it is concluded that thescallop already represents a domestic species and, considering theoccurrence and development of selection practices in sea farms,biodiversity within the species appears to be at risk. With the developmentof culture practices over its entire range, there is little use in trying torecover a wild fishery for this scallop. It is urgent, however, that selectednatural beds be protected in order to preserve genetic diversity.  相似文献   

18.
Hatchery release is one of the most popular management tools in fisheries, forestry and wild life management, while its negative impacts on wild populations are a global concern. Research and monitoring of its impacts are generally lacking, and the usefulness of hatchery release for fisheries and conservation objectives is unclear. Here, I evaluated positive and negative impacts of worldwide marine stock enhancement and sea ranching programmes in a systematic review associated with meta‐analyses with the goal of reducing bias of the review. Vast numbers of individuals of more than 180 species are released into the wild each year, but most studies are at experimental stages to assess its potential, and empirical studies are sparse for evaluating the impact on fishery production. Most cases are economically unprofitable except for a few successful cases or unevaluated. The effects of releasing juveniles can be dwarfed by the magnitude of natural recruitment when the spawning stock produces much larger recruitment than released juveniles. Density‐dependent growth caused by competition of food can be substantial, and growth rates of hatchery and wild fish and other competitive species can simultaneously be reduced when stocking exceeded the carrying capacity. Relative reproductive success can vary depending on the species, seed quality and environmental factors. Empirical studies show evidence of substantial gene flow from hatcheries, but fitness reduction in stocked populations has not been reported. The results represent the current state of worldwide marine stock enhancement and sea ranching activity and provide key information for growing fields of artificial propagation and conservation.  相似文献   

19.
20.
An assessment of vulnerability in Alaska groundfish   总被引:1,自引:0,他引:1  
Federal fishery management rules in the United States have recently changed, necessitating an examination of which fish stocks require annual catch limits and how appropriate stock complexes are formed. We used an analytical approach termed productivity-susceptibility analysis (PSA) to analyze the vulnerability of federally managed Alaska groundfish stocks to overfishing. The focus of the effort was non-target stocks that have limited data available for determining stock status and vulnerability. The PSA approach was originally created to assess risks to bycatch in Australian trawl fisheries and compares productivity attributes (e.g. life-history traits) to factors that determine a stock's susceptibility to fishing impacts, producing a combined score indicative of a stock's relative vulnerability to overfishing. We used a form of the PSA developed by a working group from the U.S. National Marine Fisheries Service specifically for use in assessing vulnerability in federally managed fisheries. Alaska groundfish displayed a wide range of vulnerability scores, and this result was mainly due to variability in productivity scores. Susceptibility scores varied less than productivity scores and were centered on an intermediate value. The inclusion of target stocks in the PSA was valuable for assessing the relative vulnerability of the non-target stocks. Sensitivity analyses indicated that PSAs respond differently to changes in attribute scores depending on their initial conditions, and managers should be careful in interpreting changes in PSA results when stocks are re-evaluated.  相似文献   

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