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1.
Abstract –  Many floodplain lake fish communities have been influenced by large-scale shifts in processes of water-level stability that degrade habitat quantity and quality. Efforts to restore rivers and their floodplains have recently taken a priority yet many restoration approaches are in their developmental stages and potentially controversial. We measured fish community changes in response to a water stabilisation technique in an Illinois River floodplain lake, achieved by levee renovations in 1997, using data collected prior to (1991–1993) and after (2000–2002) stabilisation. Our results indicate fish community composition (presence/absence) showed little variability and did not differ ( R  = 0.037; P  = 0.60) between the two time periods; whereas, fish community structure (abundance) differed ( R  > 0.50; P  ≤ 0.10). Increased abundances of desirable species like gizzard shad Dorosoma cepedianum (Lesueur), white crappie Pomoxis annularis (Rafinesque), black crappie Pomoxis nigromaculatus (Lesueur) and largemouth bass Micropterus salmoides (Lacepede), coupled with declines of less desirable species like common carp Cyprinus carpio (Linnaeus) contributed to community changes. These changes suggest positive responses to water stabilisation practices that may act as an intermediate step in restoring river–floodplain function in certain situations.  相似文献
2.
Behaviour and growth of juvenile brown trout exposed to fluctuating flow   总被引:1,自引:0,他引:1  
Abstract –  Parr of brown trout ( Salmo trutta L.) were exposed to constant or fluctuating water level and flow in artificial outdoor stream channels during 21 days in three consecutive runs, and their individual behaviour and social interactions were monitored. Despite the large variation in flow, no clear differences in growth, which was generally poor, and behaviour were found between treatments. The signs of a social structure in the stream channels were very subtle and there were no clear relation between growth rate and aggressive/dominant behaviour in any of the treatments in accordance with findings in studies of growth and dominance in the wild. Thus, in regulated rivers, daily fluctuations in flow and water level (hydropeaking) are not likely to alter the behaviour of juvenile brown trout or affect their energy turnover negatively. Several studies now indicate that if stranding can be avoided, hydropeaking has relatively small direct effects on stream salmonids. Therefore, future research should focus on cascading ecological effects that may influence the productivity of the ecosystems in regulated rivers.  相似文献
3.
水位作为重要的湖泊水文因子,对湖泊水动力过程、化学过程和生态过程具有重要的影响。根据2007~2008年鄱阳湖湖口水位、水环境实测数据,分析了湖口水位及水体各环境因子的变化特征,阐述了各水环境因子对水位变化的响应,并建立了水位与各水环境因子的回归方程。结果表明:湖口的水位及各水环境因子均呈季节性变化,湖口水位与长江水位(九江站)呈直线正相关;湖口的水位变化对其水体各环境因子均存在明显的影响,其中水体透明度随水位上升而增大,悬浮物、溶解氧、高锰酸盐指数、氮化物和磷化物浓度随水位上升而下降。  相似文献
4.
Abstract The abundance of 0+ pikeperch, Stizostedion lucioperca (L.), in trawls was compared with water temperature, water level and commercial catches 6–9 years later. The abundance of juveniles in autumn was positively correlated with the water temperature but not with water level in May or in June. The sum of a year abundance of juveniles showed a strong correlation with the catch years later. This abundance and the cumulative water temperature between August and October inclusive in five consecutive years one year prior to recruitment into the commercial fishery explained 86% of the variation in catches. This empirical model indicates that catches of pikeperch depend on both juvenile abundance and water temperature.  相似文献
5.
Abstract –  Minnow trapping was used to determine the distribution and abundance of two small, benthic species of fish, common bullies ( Gobiomorphus cotidianus ) and koaro ( Galaxias brevipinnis ), in five oligotrophic lakes varying in both turbidity and the extent of water-level variation. Koaro were 5–20 times more abundant in the large turbid lakes than in the clear ones, indicating that turbidity may reduce the extent of salmonid predation on koaro. However, the scarcity of koaro in the clear lakes was related mainly to the prevalence of brown trout ( Salmo trutta ) compared with rainbow trout ( Oncorhynchus mykiss ) as the former were more piscivorous and had a stronger inverse relationship with koaro. Common bullies were more abundant at sites 20 m or more away from the shoreline, and at depths of 9–12 m irrespective of season, year and turbidity level. However, the overall abundance of bullies was reduced by 70–90% in the turbid lakes. As bullies are relatively insensitive to the direct effects of increased turbidity, indirect effects such as reductions in macrophytes from reduced water clarity or smothering of benthic habitats by settled solids are thought to influence their abundance in the lakes affected by glacial turbidity. There was no relationship between the extent of water-level fluctuation and the abundance of koaro or common bullies in the lakes, but the depth distribution of bullies was shallowest in the lake with the least water-level fluctuation and was deepest in the lake with the greatest water-level fluctuation.  相似文献
6.
研究青海湖水文变化特征,为区域水资源管理、生态保护提供基础。利用1956-2017年青海湖水文气象及遥感资料,分析了水位、面积、水量变化情况,并从湖泊补给的构成角度分析了变化原因。结果表明,青海湖平均水位3194.50m,1956-2004年湖水位呈下降趋势,由于降水量和入湖径流量增加,2005年水位开始回升;青海湖平均面积4350.61km2,经历了先萎缩、后扩张的变化过程;湖泊边界主要是东岸、西岸、北岸发生了变化,南岸基本无变化;水量仍然处于负平衡,年均亏损量1.5×108m3;湖泊补给水量构成中,湖面降水量、地表入湖径流量、地下水入湖补给量分别约占40.3%、43.5%、16.2%;2005年以来地表入湖径流量增加主要是由气候变化引起的,降水起主导作用。  相似文献
7.
为了解灰化苔草(Carex cinerascens)对淹水水位及持续时间的生态响应,通过模拟实验研究了不同水深(对照、部分淹水、完全淹水)、不同淹水持续时间(50天、100天)条件下灰化苔草的生长、分株及物质分配等的变化情况。结果表明:总生物量随着水位上升及淹水持续时间延长而下降;淹水显著降低了株高、减少了分株数,退水后分株数因为“秋草”现象有所上升;生物量分配方面,叶、根状茎分配比上升,不定根分配比下降。虽然淹水抑制了灰化苔草的生长,但整个实验期间无植株死亡。灰化苔草通过调整自身生长来适应淹水的胁迫环境,对于理解植被分布组成、群落演替及、维持湿地生态功能等方面有积极的意义。  相似文献
8.
水文节律是河岸带植物群落演替的主要驱动因子,受水文节律影响的土壤理化特性也有可能逐渐改变周边植被,为了探究周期性淹没对三峡水库消落带植物群落及其生境状况的影响,2015年8月至9月,以三峡水库腹地万州段消落带为研究区域,调查分析了8个样地、24个样带、96个样方的消落带植被及土壤理化特征。结果表明,在三峡库区万州段消落带共调查到维管植物22科、47属、51种,其中禾本科、菊科、蓼科和莎草科的种类数较多;植物群落组成以草本植物为主,其中一年生和多年生草本植物分别占58.8%和27.5%。高程不同,群落优势种有差异,145~155 m及156~165 m区域优势度较高的物种相近,为狗牙根(Cynodon dactylon)、光头稗(Echinochloa crusgalli var. mitis)和醴肠(Eclipta prostrata);高程166~175 m区域优势度较高的物种为鬼针草(Bidens pilosa)和狗尾草(Setaria viridis)和狗牙根;高程156~166 m区域植物鲜重均值最高,为(2199.1±863.9)g/m2;高程166~175 m区域Shannon-Wiener 多样性指数和Pielou 均匀度指数的均值最高,分别为(2.00±0.30)和(0.85±0.06)。随着坡度等级增加,植物鲜重和盖度呈递减趋势,物种数在6~15°区域最高。长江左岸消落带植物鲜重、高度、Shannon-Wiener和Pielou 指数高于右岸。消落带土壤理化性质具有较高的空间异质性,土壤容重、pH、有机质、全氮、有效氮、全磷、有效磷均值分别为(1.34±0.09)g/cm3、(7.60±0.47)、(6.02±2.94) g/kg、(1.21±0.16) g/kg、(53.42±9.67)mg/kg、(0.42±0.14) g/kg、(6.55±2.82) mg/kg,其中有机质的变异系数最大,其次为有效磷和全磷。左岸消落带土壤pH、有机质、全氮和有效氮含量均值低于右岸,但左岸土壤全磷和有效磷含量高于右岸。淹没时间和土壤有效磷含量对消落带植物重要值影响较大。  相似文献
9.
基于2014年至2015年对浙江天荒坪抽水蓄能电站的监测数据,分析了水库水位变化对水体稳定的影响,并讨论了水位变化对营养盐与叶绿素a浓度的影响。结果表明:1)天荒坪抽水蓄能电站在正常运行条件下,调度模式有三种。第一种调度模式分两个阶段,先夜间零时开始蓄水至上水库,再在上午7时至夜间23时泄水至下水库;全天累计水位变幅38.03m,平均1.63m/h。第二种调度模式为夜间不蓄水,仅白天泄水,水位变幅较小;第三种调度模式则无水位变化。2)水库水体处于中营养状态,总氮对富营养贡献最大,叶绿素a次之;水位频繁变化在一定程度上减轻了抽水蓄能电站水库水体富营养化程度。3)水位频繁变化致使垂向扰动加强,水体不再稳定分层;营养物质与浮游植物受水位波动影响无法在水体中集聚,造成营养盐等物质被冲淡,藻类生长受到抑制,水体中叶绿素a含量较低。  相似文献
10.
Vendace and whitefish in Lake Osensjøen (boreal south‐east Norway) were studied by means of gillnet test fishing (1976–2013) and hydro acoustic acquisition (1986–2011). Vendace increased in number between 1998 and 2009 while growth and size at maturity decreased. The relative density of whitefish decreased in the pelagic habitat, whereas growth and size remained the same. Both species exhibited varying year‐class strength. Whereas strong year‐classes of both species became less frequent after 1980 than before this, this seemed to change after 2000, especially for vendace. Generalised additive models suggested a strong positive relationship between July/August mean air temperature and year‐class strength of both vendace and whitefish. Whitefish recruitment was also negatively affected by the new regulation regime implemented since 1981, and positively correlated with water level after hatching and by late ice off. The reason for the diverging impacts of environmental factors on the two species may be that vendace spawn in deeper waters that whitefish do. The results indicate that increasing summer temperatures benefit recruitment of both species, whereas low water level and early ice off will harm whitefish recruitment. Both trends are caused by climate warming. It may be speculated that increased density of the specialised plankton feeding vendace may affect the algal community through increased predation on herbivorous zooplankton and potentially affect the trophic state of the lake.  相似文献
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