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  1. While flooding creates diverse habitats for plants and animals in riparian ecosystems, it presents a nuisance to human settlement. Thus, such areas that are frequently disturbed by flooding are more likely to experience strong artificial control measures.
  2. This hypothesis was tested and a method was developed to identify these areas using river maps. The effects of two terrain components that could potentially influence flooding frequency (the number of confluences and the degree of meandering per unit area) on both the distribution of threatened species and the degree of artificial modification were examined at two different scales (grid sizes) using two riparian data sources.
  3. The numbers of threatened plant species and artificial constructions increased with the number of confluences and the degree of meandering per unit area. The number of threatened plant species was not correlated with the number of artificial constructions.
  4. In addition, the results suggest that confluences and meanderings provide different habitat conditions for threatened plant species. Confluences may provide more frequently disturbed habitats, whereas meanderings may provide relatively stable habitats.
  5. Based on these results, through flooding, both confluences and meanderings are important for creating and maintaining the diverse habitats used by threatened species, but these habitats are also currently threatened by artificial controls. We suggest that a per‐unit‐area confluence density and river length map is a helpful tool for locating local biodiversity hot spots. The identification of major reservoirs of biodiversity that are currently threatened can improve conservation and management planning.
Copyright © 2011 John Wiley & Sons, Ltd.  相似文献
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  1. The response of individual harbour seals (Phoca vitulina) to controlled and sporadic disturbances when hauled out in the Anholt seal reserve, Denmark, was studied. Sporadic disturbances from pedestrians, boats, low‐flying aeroplanes and grey seals (Halichoerus grypus) were observed in or near the reserve. VHF and satellite transmitters were attached to eight harbour seals to determine post‐disturbance and undisturbed behaviour during the pre‐breeding period (25 April to 21 May 2008).
  2. Both disturbed and undisturbed seals mostly returned to the haul‐out site from dusk and throughout the night. Only pedestrian disturbances caused significantly longer‐lasting trips at sea than undisturbed trips, while the other types of disturbance did not affect trip duration. The general maximum extent and area‐use of disturbed and undisturbed trips were comparable and almost all at‐sea locations were within 40 km from the haul‐out site. The maximum extent of post‐disturbance trips, however, varied among individuals and disturbance types, and was strongly correlated with the duration of trips.
  3. Disturbed and undisturbed seals used the same areas, suggesting that these areas represent normal foraging areas. This may indicate that harbour seals reduce the cost of being disturbed by foraging after disturbances instead of waiting close to the haul‐out site to resume hauling out.
  4. During the pre‐breeding period the seals showed a very high site fidelity by consistently returning to the same haul‐out site, even when subjected to repeated disturbances.
Copyright © 2013 John Wiley & Sons, Ltd.  相似文献
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为了解胶州湾海域鱼类群落粒径结构特征,本研究根据2016—2017年4次底拖网调查数据构建了胶州湾鱼类生物量粒径谱,比较分析了各季节鱼类生物量粒径谱特征参数的异质性。结果显示,胶州湾Sheldon型鱼类生物量粒径谱呈现单峰模式,鱼类粒径范围为−3~10粒径级,粒径分布相对均匀,且峰值位于5~6粒径级,主要由大泷六线鱼和褐菖鲉等小型鱼类构成。各季节鱼类标准化生物量粒径谱曲率和曲度差异显著,其中春季曲率最大且曲线较平缓,夏季曲率最小且曲线相对陡峭。谱线曲度和曲率的季节变化主要与粒径小的细纹狮子鱼、大泷六线鱼、玉筋鱼及长丝虾虎鱼等地方常栖性种类和赤鼻棱鳀、白姑鱼等季节洄游性种类的出现有关。Abundance-biomass comparison(ABC)曲线表明,春季处于未干扰状态,冬季处于中度干扰状态,夏秋季处于严重干扰状态。研究表明,胶州湾鱼类群落总体处于严重干扰状态,鱼类生物量谱呈现单峰型,粒径结构以小型粒径鱼类为主,且地方常栖性和季节洄游性鱼类等补充群体的数量和粒径大小影响鱼类生物量粒径谱的峰型和曲率。  相似文献
4.
为探究“引黄入冀补淀工程”建设下引黄口重点断面的径流情势变化及对其成因进一步分析,本文采用水文变异指标法/变化范围法(IHA/RVA法)对1958~2016年该工程实施前后两阶段的33个单项径流情势指标和整体改变度进行对比分析;并基于6种Budyko假设公式,量化分析气候变化和人类活动对径流改变的贡献率。结果显示:1)8项单项水文指标达到67%以上的高度改变,整体径流情势改变度达到61.72%;2)气候变化和人类活动对径流变化的贡献率平均值分别为41.79%和58.21%。人类活动是影响引黄入冀补淀工程引黄口重点断面径流情势变化的主要因素。  相似文献
5.
为了解胶州湾海域鱼类资源数量的时空分布特征,2016—2017年利用底拖网对胶州湾海域开展了4个航次的渔业资源调查。结果显示,胶州湾海域鱼类资源密度存在明显的季节变化。鱼类资源尾数密度以夏季最高(233 427尾/km~2),春季最低(18 080尾/km~2),秋季和冬季分别为32 246、40 746尾/km~2;鱼类资源质量密度以冬季最高(1 593.16 kg/km~2),秋季最低(337.91 kg/km~2),春季和夏季分别为681.96和825.55 kg/km~2。其中,冬季鱼类平均个体质量最大(39.10 g),夏季最小(3.54 g),春季和秋季分别为37.72 g和10.48 g。与历史调查资料相比,30多年来胶州湾鱼类资源发生了较大变化。本次调查鱼类资源密度(1 593.16 kg/km~2)低于1981—1982年(10 857.00 kg/km~2)和2008—2009年(2 196.00 kg/km~2);鱼类平均个体质量为10.60 g,低于1981—1982年(37.70 g),鱼类群落结构明显呈现小型化和低质化趋势。这些变化可能主要是由于人类活动对鱼类栖息地的破坏和海洋生态环境恶化造成的。  相似文献
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