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121.
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ANDRIJ Z. HORODYSKY DAVID W. KERSTETTER ROBERT J. LATOUR JOHN E. GRAVES 《Fisheries Oceanography》2007,16(3):240-256
Researchers have applied numerous techniques to improve billfish stock assessments, including habitat‐based models that incorporate behavioral and oceanographic parameters to standardize historical catch‐per‐unit‐effort time‐series data. These methods have allowed researchers to account for significant changes in the depths of pelagic longline (PLL) gear deployments over time. This study presents habitat‐use data recovered from high‐resolution 5‐ and 10‐day pop‐up satellite archival tags (PSATs) attached to 47 surviving white marlin released from commercial and recreational fishing gears offshore of the U.S. East Coast, the northern Caribbean, and Venezuela between 2002 and 2004. Data recovered from transmitting tags indicated that white marlin spent nearly half of their time associated with warm, near‐surface waters (<10 m). All fish displayed frequent short duration (mean: 39.8 min) vertical excursions from surface waters to depths averaging 51 m. Qualitative and multivariate classifications of data from completely transmitted movements of surviving white marlin revealed two major types of descents: one pattern was characterized by deep ‘V’‐shaped excursions of relatively short duration (mean: 23.4 min) while the other featured descents that were more broadly ‘U’‐shaped and confined to a specific depth range for an extended period of time (mean: 75.8 min). Based on the frequency, persistence, and patterns of these vertical movements, white marlin appear to direct a considerable proportion of foraging effort well below surface waters, a behavior that may account for relatively high catch rates of white marlin on some deep‐set PLL deployments. 相似文献
123.
Krystyna M. Saunders Andrew Mcminn Donna Roberts Dominic A. Hodgson Henk Heijnis 《水产资源保护:海洋与淡水生态系统》2007,17(1):51-70
- 1. Many coastal lagoons in eastern Australia have changed as a result of recent human activities. However, it is often difficult to determine the extent of change and the ecological implications. A palaeoecological approach allows a quantitative assessment of how an aquatic ecosystem changes and responds to human impacts beyond what is possible with historical data or monitoring programmes.
- 2. Orielton Lagoon (south‐east Tasmania, Australia) is a Ramsar‐listed coastal wetland of international importance for conservation. This study was undertaken at the site to determine whether recent anthropogenic hydrological modifications to the lagoon had influenced its ecology, particularly salinity, and compromised its Ramsar status.
- 3. A diatom–salinity transfer function was constructed from a training data set of 96 diatom taxa from 34 sampling sites in 19 lagoons along the east coast of Tasmania.
- 4. The salinity of Orielton Lagoon has changed in response to a causeway constructed across its mouth, which has transformed the lagoon from an open marine environment to an enclosed, virtually stagnant, brackish water body.
- 5. These changes have compromised the protected coastal wetland status of Orielton Lagoon. Environmental remediation attempts have since partially restored the natural hydrology of the lagoon and it is now returning towards the state it was in prior to causeway construction.
- 6. A palaeoecological approach using diatoms was found to be successful in reconstructing recent salinity changes and investigating human impacts on Orielton Lagoon over the last 50–55 years.
124.
Model uncertainty in the ecosystem approach to fisheries 总被引:2,自引:0,他引:2
Simeon L. Hill George M. Watters ré E. Punt Murdoch K. McAllister Corinne Le Quéré John Turner 《Fish and Fisheries》2007,8(4):315-336
Fisheries scientists habitually consider uncertainty in parameter values, but often neglect uncertainty about model structure, an issue of increasing importance as ecosystem models are devised to support the move to an ecosystem approach to fisheries (EAF). This paper sets out pragmatic approaches with which to account for uncertainties in model structure and we review current ways of dealing with this issue in fisheries and other disciplines. All involve considering a set of alternative models representing different structural assumptions, but differ in how those models are used. The models can be asked to identify bounds on possible outcomes, find management actions that will perform adequately irrespective of the true model, find management actions that best achieve one or more objectives given weights assigned to each model, or formalize hypotheses for evaluation through experimentation. Data availability is likely to limit the use of approaches that involve weighting alternative models in an ecosystem setting, and the cost of experimentation is likely to limit its use. Practical implementation of an EAF should therefore be based on management approaches that acknowledge the uncertainty inherent in model predictions and are robust to it. Model results must be presented in ways that represent the risks and trade‐offs associated with alternative actions and the degree of uncertainty in predictions. This presentation should not disguise the fact that, in many cases, estimates of model uncertainty may be based on subjective criteria. The problem of model uncertainty is far from unique to fisheries, and a dialogue among fisheries modellers and modellers from other scientific communities will therefore be helpful. 相似文献
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浅谈我院图书馆期刊管理与利用 总被引:4,自引:1,他引:3
时莉 《农业图书情报学刊》2007,19(1):66-68
阐述了辽宁农业职业技术学院图书馆期刊馆藏概况及特点,总结了期刊工作的管理实践及改革尝试和网络环境下图书馆期刊资源的开发与利用。 相似文献
129.
李蔚 《农业图书情报学刊》2007,19(2):44-46
以山东师范大学电子资源采购工作小组为例,论述了协作小组的组织结构、要素及原则,阐明了其在图书馆管理中不可缺少的作用。 相似文献
130.
孙艳 《农业图书情报学刊》2007,19(3):55-57
叙述了典藏管理的内涵和传统管理模式,分析了网络环境下对印刷型文献、电子出版物、网络虚拟资源、随书光盘的新的管理模式,提出了搞好典藏管理工作的几点意见。 相似文献