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Abstract Wild stocks of brown trout, Salmo trutta L., collapsed in Finnish inland waters during the 20th Century because dams prevented upstream migration, and low water quality and stream dredging weakened reproduction. The demise in migratory stocks was coupled with overfishing, mainly by gillnetting on lakes. Consequently, the migratory spawning stocks have diminished to negligible levels. The remaining stocks exhibit restricted immigration and emigration, are supplemented by continuous stocking, and their natural genetic diversity is affected by human activities. In recent years, various recovery actions have been implemented including stream channel restorations, fish passage facilities constructed and stocking of eggs and smolts. Gillnetting has also been regulated by banning certain mesh sizes, and catch‐and‐release of wild trout is spreading amongst sport fishers. However, these measures seem to be inadequate and almost no recovery of migratory populations has been reported. The problem of by‐catch in intensive gillnetting continues to threaten stocks and creates disputes between stakeholders. 相似文献
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Knowing how species respond to fire regimes is essential for ecologically sustainable management. This axiom raises two important questions: (1) what knowledge is the most important to develop and (2) to what extent can current research methods deliver that knowledge? We identify three areas of required knowledge: (i) a mechanistic understanding of species’ responses to fire regimes; (ii) knowledge of how the spatial and temporal arrangement of fires influences the biota; and (iii) an understanding of interactions of fire regimes with other processes. We review the capacity of empirical research to address these knowledge gaps, and reveal many limitations. Manipulative experiments are limited by the number and scope of treatments that can be applied, natural experiments are limited by treatment availability and confounding factors, and longitudinal studies are difficult to maintain, particularly due to unplanned disturbance events. Simulation modelling is limited by the quality of the underlying empirical data and by uncertainty in how well model structure represents reality. Due to the constraints on large-scale, long-term research, the potential for management experiments to inform adaptive management is limited. Rather than simply recommending adaptive management, we define a research agenda to maximise the rate of learning in this difficult field. This includes measuring responses at a species level, building capacity to implement natural experiments, undertaking simulation modelling, and judicious application of experimental approaches. Developing ecologically sustainable fire management practices will require sustained research effort and a sophisticated research agenda based on carefully targeting appropriate methods to address critical management questions. 相似文献
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运用文献资料研究、比较、思辨等方法对动作教育在儿童早期发展与教育中的意义、儿童早期动作教育的概念与内容、当前我国幼儿园动作教育现状与困境进行了阐述;指出:儿童动作学习核心经验的研究是中国早期教育中最薄弱的环节,并对进行幼儿动作教育与综合训练学习时应注意的事项等国内外热点问题进行了探讨分析,旨在为落实教育部于2012年9月颁布的《3~6岁儿童学习与发展指南》、促进幼儿的动作教育与综合身体训练的常规化、正规化提供参考依据。 相似文献
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皂苷类化合物是一大类具有多种生理功能的生物活性物质,包括抗炎、抗肿瘤、抗动脉粥样硬化、免疫调节等方面的药理作用,皂苷类的初提物通常存在有效成分含量低、杂质多、质量不稳定等缺点,在此查阅了国内外相关资料,对皂苷类化合物的主要生物活性和纯化方法进行了归纳总结,并对各方法的优缺点进行了比较,为皂苷类化合物的进一步研究提供了参考. 相似文献
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目的观察山莨菪碱和芬太尼后处理联合缺血后适应对心肌缺血再灌注兔心肌细胞氧化应激相关指标的影响。方法采用结扎兔左冠状动脉前降支30min、复灌120min建立心肌缺血再灌注模型。随机分为4组(n=8):假手术组:动脉下仅穿线不结扎;缺血再灌注组:直接恢复再灌注;缺血后适应组:结扎兔左冠状动脉前降支30min后予以3轮复灌30s/缺血30s的缺血后适应后恢复再灌注;联合用药后处理+缺血后适应组:缺血28min给予山莨菪碱5mg·kg-1、芬太尼5μg·kg-1后处理后,30min予以缺血后适应后恢复再灌注。检测各组心肌细胞超氧化物歧化酶酶蛋白活力浓度、丙二醛浓度。结果缺血再灌注组较假手术组外周血丙二醛浓度明显升高(P<0.01),超氧化物歧化酶酶蛋白活力明显降低(P<0.01)。缺血后适应组较缺血再灌注组外周血丙二醛浓度明显降低(P<0.01),超氧化物歧化酶酶蛋白活力浓度明显升高(P<0.01)。联合用药后处理+缺血后适应组较缺血后适应组外周血丙二醛浓度明显降低(P<0.01),超氧化物歧化酶酶蛋白活力明显升高(P<0.01)。结论心肌缺血再灌注可导致兔外周血丙二醛浓度升高,超氧化物歧化酶酶蛋白活力降低;缺血后适应可显著降低心肌缺血再灌注兔外周血丙二醛浓度,提高超氧化物歧化酶酶蛋白活力,其中山莨菪碱及芬太尼后处理联合心肌缺血后适应较之缺血后适应可显著降低心肌缺血再灌注兔外周血丙二醛浓度、提高超氧化物歧化酶酶蛋白活力,具有减轻心肌缺血再灌注损伤的作用。 相似文献
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华南虎哺乳期母幼行为的初步研究 总被引:2,自引:0,他引:2
对梅花山华南虎繁育研究所内 4号母虎及其所产幼虎的母幼行为进行了初步研究 ,着重描述了华南虎母幼的各种行为 ,并对其中的一些行为作了初步探讨。母幼间接触的部位主要是头部等感官较敏感区域 ,通过各种接触是建立母幼友好、亲昵关系的主要途径。母虎主要通过哺乳、舔、嗅等行为与幼虎接触 ,其次是拱、衔、护幼行为等 ;而幼虎主要是通过吮乳、舔、嗅闻与母虎接触 ,其次是叫等方式 相似文献