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81.
82.
《Marine Policy》2015
In this study, utilization of catch-quota balancing mechanisms in the Icelandic demersal fishery, which allow for individual transferable quota to be transformed among species and transferred between years, is analyzed to determine whether annual catches closely adhere to total allowable catches on average. Icelandic landings data for 14 demersal fish species during 2001–2013 are compared to implemented total allowable catches as well as catch limits recommended by the Marine Research Institute (MRI) and a proxy for annual market values. Landings surpassed legal limits of total allowable catch in 27% of the cases (landings by species by fishing year), mostly due to species transformations, but TAC overages were not consistent for any species. Instead, catches of some species were consistently less than legal limits, with some indications that landings were related to profitability (i.e. landings were correlated with market value). However, landings surpassed MRI recommendations in 67% of the cases, and landings of four species (Atlantic wolffish, haddock, monkfish and redfish) consistently exceeded MRI recommendations. Therefore, discrepancies between scientific recommendations for catch limits and quotas selected through the political process may represent a higher risk to long-term sustainability than catch-quota balancing mechanisms. 相似文献
83.
《Marine Policy》2015
Balancing catch with annual catch entitlement (ACE) is crucial both for the financial viability of fishers and for the efficient operation of the New Zealand quota management system (QMS). This study examines the information channels that are used by fishers to search for ACE availability, and notes how these channels differ between large and small fishers. Special attention is given to the viability of small independent fishers whose participation in the fishery is dependent on their acquiring ACE in the open ACE market. An ACE market survey along with extensive consultation captured the views of fishers, fish processors, and quota brokers. These sources provide valuable insights into the day-to-day operation of the ACE market. They suggest that while elements of market power are evident in the ACE market there are also characteristics of an efficient market. 相似文献
84.
2004年北太平洋柔鱼钓产量分析及作业渔场与表温的关系 总被引：1，自引：0，他引：1
根据2004年5~11月我国鱿钓船在北太平洋生产数据,结合表温资料,按经纬度1°×1°的格式,利用Marineexplorer 4.0软件作图进行柔鱼钓产量及渔场与表温的关系分析。结果表明,5~7月在160°E以东海域作业,产量较低;8~10月在150°~160°E海域作业,为生产作业的产量高峰期,占总产量的62.5%;11月在150°E以西海域作业,产量也较低。在150°E以西海域CPUE最高,150°~160°E中部海域次之,160°E以东海域最低。作业渔场的适宜表温呈现出季节性变化。各月适宜表温分别为:5月12~14℃;6月15~16℃;7月14~16℃;8月18~19℃;9月16~17℃;10月15~16℃;11月12~13℃。 相似文献
85.
风场变形误差是降水观测误差最主要的来源之一,其不仅影响观测值的准确性,也可能导致长期降水变化趋势中隐含虚假成分。结合北京地区20个气象站点1976-2015年逐日观测资料及前人研究成果,评估了风场变形误差对降水记录及其长期变化趋势的影响,结果表明:①近40年来北京地区平均降水捕获率为90%~95%,上升趋势较明显,但空间分布不均匀。城市化进程导致的风速减小是近10年来北京城、乡降水捕获率差异加大的主要原因。②北京地区风场变形误差存在明显的年际及季节差异。近40年来年均降水量订正值为23.1 mm,观测值较实际降水量年均低估了4.0%。订正后年均降水强度从实测的7.9 mm/d增加到8.3 mm/d,年降水量的下降速率从34.4 mm/10 a变为37.0 mm/10 a,观测值将降水强度低估了约4.8%,且将降水量的下降趋势低估了约7.0%。③对于强度越大的降水过程,风场变形引起的观测误差也越明显。对比发现,城市站点的风场变形误差年际振幅要大于乡村站点,弱降水过程中乡村站点的低估比城市站点明显,对大雨及以上强降水过程则相反,城市站点的低估比乡村站更显著。 相似文献
86.
为了充分利用茶叶的性能以及开发新型功能保健茶，研究了沏茶时绿茶对金属离子镉(Ⅱ)的捕集行为。笔者试验了不同酸度、温度、沏茶时间对茶叶捕集镉(Ⅱ)离子的影响，并通过改变镉（Ⅱ)标准溶液加入量考查了绿茶对镉(Ⅱ)离子的捕集容量及捕集率。结果表明，在适宜条件下(pH=7、温度控制90℃、沏茶时间为20min)，绿茶对水溶液中微量镉(Ⅱ)的捕集率最大可迭80％以上。此结果对减小茶水中镉离子对人体的影响具有一定的现实意义。 相似文献
87.
众所周知,对有效信息较少的渔业资源进行资源评估面临很大的挑战,而贝叶斯方法在数据数量较少、质量较差的情况下能利用其它种群高质量的数据或已知的先验信息提高资源评估结果的可靠性。由于印度洋长鳍金枪鱼的数据质量较差而数据量有限,长鳍金枪鱼的资源评估结果存在很大的不确定性,为此,本文以印度洋长鳍金枪鱼的资源评估为例,以调查贝叶斯方法在有效信息较少的资源评估中的优势。本文根据不同的先验假设与捕捞数据系列,共构建了8个贝叶斯动态产量模型,以评估长鳍金枪鱼资源。结果表明:(1)分析参数的后验分布能提高捕捞数据系列选择与参数假设的合理性; (2) 利用种群统计学方法为内禀增长率(r)构建有信息先验,能提高资源评估结果的可靠性。与传统方法相比,当基于贝叶斯框架时,能将已知的知识表示为先验信息并能分析参数的后验分布,从而在数据较少或数据质量较差的情况下,能利用各种信息提高参数估计的合理性与资源评估的可靠性。因此,对数据量较少或数据质量较差情况下的渔业资源评估而言,贝叶斯方法非常有效,如本文所示的印度洋长鳍金枪鱼的资源评估。 相似文献
88.
K. F. Walker I. G. Dunn D. Edwards T. Petr H. Z. Yang 《International Journal of Salt Lake Research》1995,4(3):169-222
Quinghai Hu is a large, high-altitude, saline lake in north-western China, and supports a fishery based on an endemic species of naked carp (snow trout). The fish take seven years to attain maturity and a marketable weight of 300 g, and have a lifespan of 14–21 years under the present fishery regime. They seasonally migrate from the lake to spawn over the gravel beds of inflowing rivers, but these areas have been reduced by weirs and irrigation diversions and recruitment may have declined. The population may have been affected also by a 1.85-m fall in the lake level over the past 30 years, and by associated changes in salinity. The fishery was opened to large-scale exploitation in 1958. Yields declined sharply (max. 28,523 tonnes, 1960) as the larger, older fish were removed, and then more slowly (min. 2523 tonnes, 1983). Since 1987 the fish factory has been limited to an annual quota of 1200 tonnes, taken by a fleet of four pair trawlers. Another 800 tonnes are taken by licensed fishermen, mainly using gill nets, and perhaps 1000 tonnes are taken illegally. The estimated total catch in 1992 was 3000 tonnes. New trawlers introduced in 1989–90 substantially increased the factory's catch per unit effort, and in 1990 the quota was virtually filled in one month in a zone within 20 km of the factory. Although this could suggest that the stocks will be conserved if the quota is retained, at least half of the catch in 1989–92 consisted of immature individuals. Trawling operations recently were suspended following a further decline in the catch after 1992. While the new trawlers are capable of a major increase in effort, neither the changing environment, the fish stocks or the present markets favour intensified pressure. Gillnets may provide better control over the minimum size limit and may cause less damage than trawling. Other options to improve the viability and profitability of the fishery include improvements in handling, processing and marketing. Failure to develop the fishery may encourage attempts to introduce exotic fish, at some risk to survival of the local species. 相似文献
89.