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Marzia Bo Martina Coppari Federico Betti Francesco Enrichetti Marco Bertolino Francesco Massa Simone Bava Guido Gay Riccardo Cattaneo-Vietti Giorgio Bavestrello 《水产资源保护:海洋与淡水生态系统》2021,31(3):543-566
- Seamounts host some of the most important deep-sea ecosystems. The unique environmental characteristics of seamounts sustain rich biological hot spots, which, in recent times, have suffered the effects of intense fishing pressure.
- Biodiversity and vulnerability data are extremely scarce for Mediterranean seamounts, and this, in addition to the complex socio-economic and juridical status of offshore sites, results in difficulty in identifying the best management strategies.
- An extensive remotely operated vehicle (ROV) survey was used to characterize the megabenthic assemblages of the summits of two upper bathyal seamounts, Ulisse and Penelope (Ligurian Sea, north-west Mediterranean Sea). The biogeographic implications of these findings and the possible environmental factors favouring the occurrence of these communities are discussed.
- High densities of abandoned, lost, or otherwise discarded fishing gear (mainly longlines) and a reduction in the average size of the fragile and slow-growing habitat-forming gorgonian Callogorgia verticillata indicate the occurrence of high levels of anthropogenic impacts on the summit regions, which are fishing grounds for artisanal and recreational fishers.
- The recovery of fishing data describing the first catches in the 1970s proved to be useful in inferring the short- and long-term effects of fishing practices in these previously unexploited offshore areas. In particular, the local extinction of demersal top predators, subjected to exceptional catches nearly 50 years ago, highlights the slow recovery rate of such species.
- Criteria defining vulnerability are discussed for the two study areas, and specific conservation actions, including the creation of regulated protected areas, are proposed.
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证券技术分析自诞生以来,其合理性和有效性就一直受到了普遍的关注。有些人认为技术分析的作用非常有限,甚至是毫无根据和无效的。这一种观念在有效市场假说创立以来更上升到了理论的高度。本文认为,技术分析作为一种在证券投资中被广泛应用的预测股价变动的工具,具有一定的内在合理性因素,可以用来对股价变动的趋势作出预言。但必须指出:技术分析的科学性尚不能得到承认。 相似文献
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本文首先介绍了小概率原理和假设检验的基本概念,其次又给出了关于总体平均数及总体频率的假设检验方法,可详细地分为双侧检验与单侧检验。最后,又列举了一些如何利用假设检验的实例,这些例子都具有一定的参考价值与使用价值。 相似文献
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郑家顺 《安徽农业大学学报》2010,(5):114-116
根据 Richard Day 提出的大学英语泛读课教学“i- 1 假想”,结合我国传统教育思想,从运用机制方面阐述这一假想的理论和实际意义。这一泛读假想的应用将有利于在现代化教学手段中转换教师角色,提高学生的实践量和参与程度,通过在自然学习过程中把语言知识转化为交际能力,培养学生的自主学习能力。 相似文献
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种子传播的生态学特点 总被引:3,自引:0,他引:3
本文评述了种子和果实对传播的各种适应,介绍了关于传播的有关假说,并且讨论了种子和果实适应于传播的生态学意义。 相似文献
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以西方经济学中最基本的经济人假说为研究起点,基于一个新的理论假说,给出对农民专业合作行为的广义经济学分析,并结合新的研究结论阐述其政策含义。经济人的经济利益圆周范围不断扩大以至相互重叠,是合作行为产生的客观经济基础;农民专业合作行为产生的重要前提是家庭土地承包经营的充分发展,并始终以此为基础;农民专业合作的经济效率来源于参与者的合作收益,但必须保证合作收益大于合作成本;农民的合作净收益必须留存于合作组织内部,合理、均衡的利益反馈机制是保证其可持续运行的关键。 相似文献