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于1985—1988年对前额间银鱼生物学特性、资源变动状况及其原因进行了现场和社会调查。调查表明,前颌间银鱼资源变动的原因是南、西区和吴淞口三大污染源对其生态环境严重污染;同时还有多年持续过捕超过其再增殖能力。为此,提出治理污染,恢复前颌间银鱼的生活环境及保护繁殖亲体的对策和建议。 相似文献
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We describe industry funded contributions to the assessment of the SNA1 snapper (Pagrus auratus) fishery during the 1990s and discuss the advantages and disadvantages of industry funded research. We also provide background on the history of fisheries management in New Zealand, on the current assessment and management processes, and on the SNA1 snapper fishery. In the SNA1 fishery, the contributions of industry and the cooperation with Government scientists has resulted in high quality assessments. In our opinion, the advantages of industry funded research out weigh the disadvantages and suggest that industry funded assessments are highly desirable and should be an integral part of any management system. 相似文献
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A new approach for the solution of the two-dimensional guillotine-cutting problem in ship production
A. Cemil Dikili 《Ocean Engineering》2004,31(8-9):1193-1203
A new approach has been developed for the arrangement of rectangular pieces in plates for the guillotine-cutting problem as encountered in ship production and similar manufacturing processes. The algorithm is quite novel in the sense that instead of making preliminary specifications and ignoring all the alternative arrangements, as is the case for most of the current models, it selectively considers feasible arrangements by eliminating the majority of the probable arrangements that render the problem insolvable. Intermediate steps of the algorithm produce results which cannot be obtained through integer programming. Losses are distributed to the minimum number of plates. The number of arrangement plans is also minimized. Overall the solution of the problem has been drastically simplified to allow even hand calculations instead of long computer runs. 相似文献
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The results of a 2007 survey of fishers, managers, scientists, and enforcement officials indicate that noncompliance is a significant problem in the Northeast multispecies groundfish (NEGF) fishery, as it has been for at least 20 years. The percent of total harvest taken illegally is estimated to be 12–24%, which is significantly higher than estimates of 6–14% in the 1980s. Thirty-seven percent of fishers, 61% of fishery managers and 80% of fishery enforcement staff believe that “the combined adverse impact of all violations on the health and manageability of fish resources” is significant, highly significant, or extremely significant. Many fishers believe that illegal fishing will prevent them from ever benefiting from stock rebuilding programs. 相似文献
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利用2009-2010年四个季度月用底栖生物抓斗式采样器捕获的文昌鱼样品,从其资源分布、年龄结构、生物学和生态学特征等方面对厦门国家级珍稀海洋物种自然保护区文昌鱼的种群健康状况进行评价研究.结果表明:(1)文昌鱼种群资源分布衰减趋势明显,只在黄厝—前埔海区、小嶝岛—角屿海区和南线—十八线海区3个核心区还有分布,但资源密度低,分布范围狭小,而在鳄鱼屿实验区未能发现.(2)文昌鱼体重与体长之间关系:W=6.6895×10-4L3.1818;体长与体质量生长方程分别为:厶=65.63[1-e-0.68(t+032)],Wt=404.62[1-e-0.68(t+032)]3.1818;夏季、冬季航次的优势体长组分别为25-35mm和35-45mm,优势体重组分别为25-50mg和50-100mg;秋季低龄鱼较多,而冬季高龄鱼比例较高.(3)采用ELEFAN Ⅰ技术分析了厦门文昌鱼的Von Bertalanffy生长参数K、L∞、总死亡系数Z、自然死亡系数M和开发率E,发现其生长参数K值较大,自然死亡系数较高,开发率较大(0.69).综之,厦门自然保护区内的文昌鱼种群健康状况整体不佳,应注意资源保护,加强保护文昌鱼栖息地的底质和水质以及防止过度捕捞以实现其资源可持续利用. 相似文献
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头石山尾矿库存在坝址地基土稳定性差和库址渗漏等地质问题,认真研究处理,以确保尾矿库设计合理和坝体安全及投入使用后运行正常。 相似文献
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《Marine Policy》2014
Korea's coastal and offshore fisheries have experienced reduction in their catch in the early 2000. The amount of catch from coastal and offshore fisheries dropped from 1.7 million tons in 1986 to 1 million tons in 2004. To address such catch reduction, fish stock enhancement programs have been constantly developed and implemented. However, as fish stocks have been estimated to decrease since 2000 in spite of various management measures, the Korean Government genuinely acknowledges the necessity to enhance fisheries productivity through the recovery of depleted fish stocks. Based on such acknowledgement, a fish stock rebuilding plan (FSRP) combined with conventional fish stock enhancement programs was established in 2005. For stocks which have shown drastic decrease, a FSRP was set up and promoted. So far, 10 FSRPs have been established and operated, and plan is being made to expand them to 20 species by 2012. The result of pilot projects shows that stocks have been increasing after the introduction of FSRPs. For instance, the catch per unit effort (CPUE) of sandfish in the East Sea has increased from 0.44 in 2005 to 0.78 in 2011. Consequently, fishing income has increased by 15%. The key lessons learned during the implementation of FSRP are: the causes for the decrease of stock vary and are complicated and it is necessary to adjust and eliminate some conventional policies that could have unforeseen negative impacts on fish stocks. The FSRP-based fisheries management policy in Korea carries great significance, for it has changed the focus of policy from simply maintaining the status quo to stock recovery and it allows relevant stakeholders to get actively involved in the procedures of establishing and promoting the plan, leading to effective implementation of the plan. The current FSRP is operated with species, but if it can be gradually expanded to encompass the whole ecosystem, it will greatly contribute to more effective management and fish stock recovery for all species in offshore and coastal waters surrounding Korea. 相似文献
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In 1994, a directed fishing moratorium was declared for Grand Bank American plaice (Hippoglossoides platessoides) and yellowtail flounder (Limanda ferruginea) stocks because both stocks showed severe declines in abundance from heavy exploitation during the mid 1980s and early 1990s. Four years later, the fishery for yellowtail re-opened while the plaice stock has shown little recovery and the moratorium is still in effect. To assess the possible causes of the differences in recovery between species, we examined the spatial structure and environmental characteristics of the continental shelf nursery habitats of plaice and yellowtail, and their relationship to recruitment variability and overall population size. Depth plays a major influential role determining the spatial pattern and the abundance of juveniles of both species and in the case of plaice the spatial structure of the adult population also determines the amount of nursery area utilised by juveniles. Recruitment variability was higher in plaice than in yellowtail. We found year class synchrony in both species indicating that common environmental conditions and/or biological processes are affecting recruitment in a similar manner. Density-dependent regulation appears to be more severe in yellowtail and this should contribute to a more stable population when compared to plaice. These results are discussed in terms of resiliency of both stocks to over-exploitation. 相似文献
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《Limnologica》2015
Morphometric differences were used to elucidate the stock geographic variations and phylogeography of Macrobrachium nipponense in Taiwan. Eight samples were collected from three estuaries (Tamsui River Estuary [TSE], Kaoping River Estuary [KPE], and Houlung River Estuary [HLE]) and five reservoirs (Shimen Reservoir [SMR], Mingde Reservoir [MDR], Deji Reservoir [DJR], Tsengwen Reservoir [TWR], and Chengqing Lake Reservoir [CLR]). Twelve morphometric measurements were size-standardized by the allometric method and via Cluster Analysis and Canonical Variate Analysis (CVA). Randomisation tests were used to verify the morphometric variation between groups. The results clustered the eight samples into a minimum of three groups. The first group included four reservoir samples (i.e. DJR, MDR, CLR, and TWR); the second included the SMR sample, and the third comprised the remaining estuarine samples (i.e. TSE, HLE, and KPE). Morphometric variation among the three groups was significant for each sex. Significant differences between these three groups may be derived from evolutionary origins, geographic events or environmental adaption which was discussed in the paper. The difference between multivariate allometric coefficients in both sexes and sites were also tested based on the eight group data sets, and the result showed that the difference between sexes was significant. 相似文献