Invasive tilapia juveniles are associated with degraded river habitats     

Ana R. Linde  Jorge I. Izquierdo  Josino Costa Moreira  Eva Garcia‐Vazquez 《水产资源保护:海洋与淡水生态系统》2008,18(6):891-895

• 1. Invasions are a main concern for conservationists. Identification of causes that raise or promote an invader's success is one of the first steps for preventing and/or fighting against invasions.
• 2. In the Brazilian River Paraiba do Sul, juveniles of invasive tilapia Oreochromis niloticus were detected associated with degraded habitats (mainly pollution from various sources). The relative abundance of juveniles of the competitor native species pearl cichlid Geophagus brasiliensis, morphologically and ecologically very similar, was negatively associated with habitat degradation.
• 3. A species‐specific molecular marker was employed to permit unambiguous identification of these small juveniles (2–3 cm long), which represent the most vulnerable life stage of both species.
• 4. It is suggested that adaptation to degraded habitats is one of the characteristics of invasive species, and consequently habitat conservation and restoration may help to prevent fish invasions.

Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

广东鹤山主要森林生态系统酸沉降影响现状研究     

刘菊秀  周国逸  温达志 《农业环境科学学报》2003,22(4):430-433

通过野外现场采样及室内分析方法,对广东鹤山主要森林生态系统酸沉降影响现状进行了研究。结果表明,鹤山森林生态系统林内降水、地表水和土壤酸化比较严重。林内降水pH值较低(<4.8)。通过降水析出的阳离子总量大于阴离子总量,林冠层负电荷相对较多,易吸附H+。地表水较之大气降水pH值有所升高,然而阳离子含量高,大量的营养离子流往林外。不管是针叶林还是阔叶林0～10cm层土壤都表现出很强的酸化现状,盐提pH值在4.0以下,土壤交换性酸含量高,而盐基饱和度却较低。酸沉降对鹤山森林生态系统影响较严重。  相似文献   

Models of predation and fishing mortality in aquatic ecosystems   总被引：8，自引：1，他引：8  

Stuart J Whipple  Jason S Link  Lance P Garrison  & Michael J Fogarty 《Fish and Fisheries》2000,1(1):22-40

The dynamics of fish stocks are greatly influenced by predatory and fishery removals. We describe the strengths and weaknesses of a suite of approaches that assess the scope and magnitude of fishery and predatory mortality in aquatic ecosystems. We examine: (i) empirical models for pattern detection, process exploration, and model parameterization (e.g. multispecies time series and multiple regression); (ii) qualitative process-based models of species interactions (e.g. food web analyses and loop analyses); and quantitative process-based multispecies models that include: (iii) static flow models (e.g. Ecopath ); (iv) dynamic models of either numerical abundance (e.g. Lotka–Volterra) or biomass (e.g. Ecosim and multispecies biomass dynamics); and (v) spatially explicit versions of the above. Decisions concerning a specific modelling approach should be evaluated in the context of the goals of the model and empirical database. Important considerations include model use, desired output, and management context. Four important factors to consider in model selection are the spatial and temporal extent and resolution, conservation of mass or numbers, mathematical representation of predator–prey interactions, and mathematical representation of technical interactions. We conclude that the most effective modelling exercise to achieve a given set of goals should incorporate the evaluation of multiple model configurations.  相似文献   

Coastal catch transects as a tool for studying global fisheries     

Reg Watson  Daniel Pauly 《Fish and Fisheries》2014,15(3):445-455

We present a new, intuitive approach for the representation of fisheries catches within profiles perpendicular to coast of the Exclusive Economic Zones (EEZ) of countries, or of Large Marine Ecosystems (LME). These ‘catch transects’ show where catch is extracted in the water column and near the sea bottom on plots of log‐bathymetry versus log‐distance offshore and thus allow for representation of the catch density of pelagic and benthic fisheries. Hence, they also allow direct visual comparison of the intensity of fishing through time and space. The California Current, North Sea and the South China Sea LMEs and the EEZs of Australia, Canada, Chile, China, India and Thailand are presented as examples, revealing the general intensification and extension of fishing offshore and into the depths over the decades from the 1950s. Catch transects reveal how these trends have accelerated in some areas, but surprisingly have reversed themselves in some others. It is proposed that these catch transects will be particularly useful for communicating the results of large‐scale fisheries studies to a wide spectrum of groups ranging from the fishing industry to the general public.  相似文献   

How to link biomanipulation and sustainable fisheries management: a step-by-step guideline for lakes of the European temperate zone   总被引：7，自引：0，他引：7  

T. Mehner  & R. Arlinghaus  S. Berg  H. Dörner  L. Jacobsen  P. Kasprzak  R. Koschel  & T. Schulze  C. Skov  & C. Wolter  & K. Wysujack 《Fisheries Management and Ecology》2004,11(3-4):261-275

  相似文献   

不同枣园生态系统中昆虫群落及其多样性   总被引：50，自引：3，他引：50  

师光禄  曹挥  戈峰  夏乃斌  李镇宇 《林业科学》2002,38(3):94-101

对太谷地区枣园不同生态系统中昆虫群落及其多样性进行了研究。结果表明，在5种类型的枣园昆虫有209种（包括螨类），它们分别隶属于13个目（包括蜱螨目），80个科；不同枣区昆虫群落的科数，物种数及其丰盛度均有不同程度的变化。在不同生境集中性指数也有一定的差异；全年各园的优势和中主要以刺吸式口器的蚧虫为主，偶发性优势种是朱砂叶螨，枣飞象和枣尺蠖；昆虫群落及各类群生态优势集中性在不同枣园及不同季节并不一致。  相似文献   

枣园生态系统中主要害虫、天敌种群动态的研究     

冯津  李登科  杜学梅  刘素琪  曹挥  师光禄 《山西农业大学学报(自然科学版)》2005,25(4):350-352

为了控制枣树害虫,对太谷地区枣园生态系统中主要害虫、天敌的种群动态进行了调查研究。结果表明,⑴在五种不同类型的枣园区发现的昆虫共有209种(包括螨类),它们分别隶属于13个目,80个科;⑵不同的间作管理园,主要害虫、天敌种类组成有明显差异。无杂草园的害虫和天敌的比值是有杂草园的5.66倍;喷过药的枣麦间作园是未喷药的5.73倍;喷过药的枣麦与枣豆间作园的害虫和天敌的比值无明显差异;⑶在不同间作管理园,害虫数量的增减趋势与天敌是一致的,但天敌峰值基本上落后于害虫10~20 d;⑷主要害虫和天敌丰盛度的变化是由于少数极丰盛种类的增减而引起的,在枣树整个生长发育过程中,不同的生育期,害虫和天敌的优势种也有差异。  相似文献   

森林生态系统服务功能价值评估方法研究综述   总被引：14，自引：0，他引：14  

康文星 《中南林学院学报》2005,25(6):128-131,145

森林生态系统是陆地上最为复杂的生态系统，它不但拥有丰富的资源，还具有巨大的环境调节功能和生态社会效益，介绍了森林生态系统中没有普通意义上的市场的一些生态服务功能价值评估和计算方法，并评价了这些方法的优劣；系统阐述了森林生态系统提供林产品、涵养水源、防洪效能、保持水土、保持养分、防止泥沙淤积、固定CO2、释放O2、吸收SO2、截留粉尘和净化大气功能的生态价值评估方法。  相似文献   

农业土壤中汞的生物地球化学行为及其生态效应   总被引：5，自引：0，他引：5  

洪春来  贾彦博  杨肖娥  翁焕新 《土壤通报》2007,38(3):590-596

综述了国内外近年来农业土壤中汞的生物地球化学行为,包括了土壤环境中汞的来源,汞的形态和生物有效性,汞在农业生态系统中的迁移和转化途径,影响汞对植物有效性的主要因子。同时讨论了汞对植物、动物生长发育的影响,特别强调了土壤中汞污染对食物中汞积累和分配的影响及通过食物链途径给人类健康带来的危害。最后提出了汞污染土壤的各种修复措施,展望了今后研究的方向。  相似文献   

Consistent patterns of N distribution through soil profiles in diverse alpine and tundra ecosystems     

M.I. Makarov  T.I. Malysheva  J.H.C. Cornelissen  R.S.P. van Logtestijn  B. Glasser 《Soil biology & biochemistry》2008,40(5):1082-1089

We studied the vertical patterns of δ¹⁵nitrogen in total N and exchangeable NH₄⁺-N through soil profiles in diverse alpine and tundra ecosystems. Soil samples were analyzed from 11 sites located in three mountain areas: NW Caucasus (Russia), the Khibiny Mountains (NW Russia) and Abisko region (N Sweden). Despite differences in the profile patterns of organic matter, nitrogen accumulation and nitrogen availability, we found consistent patterns of ¹⁵N distribution through all studied soil profiles. The δ¹⁵N values of total N were in general about zero or positive in the surface horizon and increased with soil depth. In contrast with total N, the δ¹⁵N values of exchangeable NH₄⁺-N were in general about zero or negative in the surface horizons and decreased with soil depth. NH₄⁺-N was significantly ¹⁵N-depleted compared with total N in all mineral horizons, while in the surface organic horizons differences between isotopic composition of total N and NH₄⁺-N were mostly not significant. We do not know the exact mechanism responsible for ¹⁵N depletion of NH₄⁺-N with soil depth and further research needs to evaluate the contributions of natural processes (higher nitrification activity and biological immobilization of “lighter” NH₄⁺-N near the soil surface) or artifacts of methodological procedure (contribution of the ¹⁵N-enriched microbial N and dissolved organic N near the soil surface). Nevertheless, our finding gives a new possibility to interpret variability in foliar δ¹⁵N values of plant species with different rooting depth in alpine and tundra ecosystems, because plants with deeper root systems can probably consume “lighter” rather than “heavier” NH₄⁺-N.  相似文献