Large‐scale patterns of fish diversity and assemblage structure in the longest tropical river in Asia          下载免费PDF全文

Ratha Chea  Sovan Lek  Pengbun Ngor  Gaël Grenouillet 《Ecology of Freshwater Fish》2017,26(4):575-585

Although the Mekong River is one of the world's 35 biodiversity hot spots, the large‐scale patterns of fish diversity and assemblage structure remain poorly addressed. This study aimed to investigate the fish distribution patterns in the Lower Mekong River (LMR) and to identify their environmental determinants. Daily fish catch data (i.e. from December 2000 to November 2001) at 38 sites distributed along the LMR were related to 15 physicochemical and 19 climatic variables. As a result, four different clusters were defined according to the similarity in assemblage composition and 80 indicator species were identified. While fish species richness was highest in the Mekong delta and lowest in the upper part of the LMR, the diversity index was highest in the middle part of the LMR and lowest in the delta. We found that fish assemblages changed along the environmental gradients and that the main drivers affecting the fish assemblage structure were the seasonal variation of temperature, precipitation, dissolved oxygen, pH and total phosphorus. Specifically, upstream assemblages were characterised by cyprinids and Pangasius catfish, well suited to low temperature, high dissolved oxygen and high pH. Fish assemblages in the delta were dominated by perch‐like fish and clupeids, more tolerant to high temperatures, and high levels of nutrients (nitrates and total phosphorus) and salinity. Overall, the patterns were consistent between seasons. Our study contributes to establishing the first holistic fish community study in the LMR.  相似文献   

Selecting fish‐based metrics responding to human pressures in French natural lakes and reservoirs: towards the development of a fish‐based index (FBI) for French lakes     

L. Launois  J. Veslot  P. Irz  C. Argillier 《Ecology of Freshwater Fish》2011,20(1):120-132

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Salinity and geomorphology drive long‐term changes to local and regional fish assemblage attributes in the lower Pecos River,Texas          下载免费PDF全文

Christopher A. Cheek  Christopher M. Taylor 《Ecology of Freshwater Fish》2016,25(3):340-351

River systems throughout arid regions worldwide have been heavily impacted by human activities, resulting in long‐term ecological consequences. The lower Pecos River in the Trans‐Pecos region of Texas is no exception, having undergone anthropogenic changes that include decreased flow, elevated salinity, species loss and species invasion. We compared historical and contemporary fish assemblage attributes from the Pecos River at local (site‐specific) and regional (Trans‐Pecos region) scales across a 24‐year time period. Fish assemblage data were collected in October 1987 and 2011, by seining at 15 sites spanning 430 km of the river in Texas. Additionally, we examined contemporary environmental conditions to determine species–environment relationships. We found that fish assemblages were significantly different between time periods, likely due to increased salinisation in the upper half of the study region. Decreased species richness, species replacement and increases in euryhaline species were documented in the upstream sites. Freshwater springs lower the salinity and maintain flows in the downstream reach, allowing for maintenance of the native fish fauna. Careful management of regional aquifers, irrigation practices and petroleum waste water will be necessary for protecting biodiversity and environmental flows in the lower Pecos River.  相似文献   

Assemblage patterns of fish functional groups relative to habitat connectivity and conditions in floodplain lakes     

S. Miyazono  J. N. Aycock  L. E. Miranda  T. E. Tietjen 《Ecology of Freshwater Fish》2010,19(4):578-585

Miyazono S, Aycock JN, Miranda LE, Tietjen TE. Assemblage patterns of fish functional groups relative to habitat connectivity and conditions in floodplain lakes.
Ecology of Freshwater Fish 2010: 19: 578–585. © 2010 John Wiley & Sons A/S Abstract – We evaluated the influences of habitat connectivity and local environmental factors on the distribution and abundance patterns of fish functional groups in 17 floodplain lakes in the Yazoo River Basin, USA. The results of univariate and multivariate analyses showed that species–environmental relationships varied with the functional groups. Species richness and assemblage structure of periodic strategists showed strong and positive correlations with habitat connectivity. Densities of most equilibrium and opportunistic strategists decreased with habitat connectivity. Densities of certain equilibrium and opportunistic strategists increased with turbidity. Forested wetlands around the lakes were positively related to the densities of periodic and equilibrium strategists. These results suggest that decreases in habitat connectivity, forested wetland buffers and water quality resulting from environmental manipulations may cause local extinction of certain fish taxa and accelerate the dominance of tolerant fishes in floodplain lakes.  相似文献   

Priority habitats for the conservation of large river fish in the Ganges river basin     

Uttam Kumar Sarkar  Mark B. Bain 《水产资源保护:海洋与淡水生态系统》2007,17(4):349-359

• 1. Three classes of habitat used by groups of fish species classified as conservation and management priorities were developed for the Gerua River (also known as the Girwa River, Karnali River) in the Ganges river basin. This river is large (mean annual discharge ca 1500 m³ s^?1, up to 900 m wide), surrounded by protected lands of India and Nepal, and upstream of major diversions and river alterations.
• 2. Fish and habitat sampling was conducted at 45 sites from 2000 to 2003. Data were analysed for 2172 fish of 14 species. Species and life stages found occupying a statistically distinct subset of the river habitats were grouped to identify classes of river habitat for conservation.
• 3. Most species and life‐stage groups specialized on specific habitat conditions revealed by multivariate analyses of variance and a principal component analysis. The most numerous and diverse group (six species, 15 life stages) was associated with deep depositional habitats with sandy substrate. Two species covering three life stages were primarily oriented to erosional habitat marked by fast current velocity with pebble and cobble substrate. A third group of three species of adults and juveniles were intermediate in habitat use.
• 4. River conservation for fish faunas should maintain both erosional and depositional channel habitats with depths, substrates, and current velocity inclusive of the ranges reported. The erosional and depositional nature of the key habitats requires that rivers be maintained with flows capable of channel‐forming functions.

Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Seasonal dynamics of fish assemblage in a pond canal     

Jiří Musil  Zdenek Adámek  Christian Baranyi 《Aquaculture International》2007,15(3-4):217-226

The annual dynamics of fish assemblage in a pond-connecting canal of a South Moravian pond aquaculture facility was studied to reveal potential assemblage effects on pond stocks and vice versa. The species richness of fish assemblage and seasonal dynamics of its development were predominantly dependent upon the fish stock of the interconnected ponds (particularly due to escapees during the period of pond harvesting), which contributed to a considerable increase of commercial fish species occurrence. Using a seasonal parameter, the season proved to have a major impact on fish assemblage dynamics (r = −0.71, P < 0.001). Spring samples were dominated by commercial fishes of aquaculture origin (mainly Cyprinus carpio). Occurrence of several fish species originating from the wild (bleak, Alburnus alburnus, chub, Leuciscus cephalus and roach, Rutilus rutilus) was also reported. The pond canal was found to be an important reservoir site of persistent survival and potential subsequent spreading of some undesirable alien fishes such as topmouth gudgeon (Pseudorasbora parva) and gibel carp (Carrasius auratus). Moreover, more attention should be paid to the potential negative impacts of all fishes of aquaculture origin upon the natural ecosystem and to the adverse effects due to the immigration of wild fish into aquaculture pond farming units.  相似文献   

Effects of mangrove deforestation on fish assemblage at Pak Phanang Bay,southern Thailand   总被引：2，自引：0，他引：2  

Tatsuya Shinnaka  Mitsuhiko Sano  Kou Ikejima  Prasert Tongnunui  Masahiro Horinouchi  Hisashi Kurokura 《Fisheries Science》2007,73(4):862-870

Daytime sampling using a seine net was conducted at Pak Phanang Bay (Nakhon Si Thammarat Province, Thailand) in February and July 2006, to determine differences in fish assemblage structures between a mangrove site and an adjacent site completely cleared of mangroves. The overall numbers of fish species and individuals were significantly higher at the mangrove site than the cleared site in both months. Although benthic crustacean feeders showed more species and individual numbers at the mangrove site in both months, the opposite was found for zooplankton feeders. A cluster analysis, based on the abundance of each species, demonstrated that the fish assemblage structures were distinctly different between the two sites. In addition, significant differences in length frequency distributions for each of the four most abundant species were found between the sites in February and/or July. Small individuals of Scatophagus argus, Ambassis nalua, and Tetraodon nigroviridis were more common at the mangrove site, and of Chelon subviridis at the cleared site. These results suggest that mangrove deforestation exerts marked effects on fish assemblages.  相似文献   

Connectivity,habitat, and flow regime influence fish assemblage structure: Implications for environmental water management in a perennial river of the wet–dry tropics of northern Australia     

Bradley J. Pusey  Michael Douglas  Julian D. Olden  Sue Jackson  Quentin Allsop  Mark J. Kennard 《水产资源保护:海洋与淡水生态系统》2020,30(7):1397-1411

1. Environmental water management seeks to balance competing demands between the water needed to sustain human populations and their economic activities and that required to sustain functioning freshwater ecosystems and the species they support. It must be predicated on an understanding of the environmental, hydrological, and biological factors that determine the distribution and abundance of aquatic species.
2. The Daly River of the wet–dry tropics of northern Australia consists of a perennially flowing main stem and large tributaries, as well as many small to large naturally intermittent tributaries, and associated off‐channel wetlands. Increased groundwater abstraction to support irrigated agriculture during the dry season threatens to reduce dry‐season flows that maintain perenniality and persistence of freshwater fishes.
3. Fish assemblages were surveyed at 55 locations during the dry season over a 2‐year period with the goal of establishing the key landscape‐scale and local‐scale (i.e. habitat) drivers of fish species distribution.
4. Longitudinal (upstream/downstream) and lateral (river/floodplain) gradients in assemblage structure were observed with the latter dependent on the position in the river landscape. Underlying these gradients, stream flow intermittency influenced assemblage composition, species richness, and body size distributions. Natural constraints to dispersal were identified and their influence on assemblage structure was also dependent on position within the catchment.
5. Eight distinct assemblage types were identified, defined by differences in the abundance of species within five groups differing in functional traits describing body size, spawning requirements, and dispersal capacity. These functional groups largely comprised species widely distributed in northern Australia.
6. The results of the study are discussed with reference to the environmental flow needs of the Daly River and other rivers of northern Australia. The findings may also be applied to environmental flow management in savannah rivers elsewhere.

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配气机构拆装CAI课件的开发研制     

刘荣昌  陈立东  马淑英  李国昉  张亮  郑立新 《计算机与农业》2010,(4):108-110

针对基于捷达汽车发动机设计的配气机构多媒体课件,主要介绍了配气机构的基本工作原理、拆装过程及注意事项,该课件可用于发动机配气机构结构原理的讲解或作为发动机拆装实习的辅助教学。该软件主要利用3ds max 4.0制作素材,渲染成＊.bmp图片和＊.avi动画文件;利用Photoshop制作背景和按钮;利用Authorware进行整体链接和画面的调整、音乐的播放和停止、动画的播放和停止,以及帮助和退出等设计。  相似文献   

Inherent bias in using aggregate CPUE to characterize abundance of fish species assemblages     

Pierre Kleiber  Mark N. Maunder 《Fisheries Research》2008,93(1-2):140-145

We have analyzed the practice of assessing an assemblage of fish species in a multispecies fishery on the basis of aggregate catch per unit effort (CPUE), which is the summed catch of all species per unit of effort. We show that at the onset of fishing or of a large positive or negative change in fishing effort, aggregate CPUE will be hyper-responsive, that is, relative change of aggregate CPUE will be greater than that of aggregate abundance. We also show that as the fishery reaches equilibrium, the aggregate CPUE in most circumstances will continue to be hyper-responsive, with a greater relative change from its value at the start than the aggregate abundance. However, there are less likely circumstances in which the aggregate CPUE will be hyper-stable compared to aggregate abundance. The circumstances leading to hyper-responsiveness or hyper-stability depend on the distribution of productivity and fishery vulnerability parameters among the species in the aggregation.  相似文献