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1.
A qualitative comparative approach has been used to review whether fish assemblage characteristics, such as paucity of lacustrine‐adapted fish species, long food chains, and disproportionate number of piscivorous species, limit fishery yields in reservoirs of the Upper Paraná River basin. The paucity of lacustrine‐adapted species appears to limit fishery yields, but attempts to introduce lacustrine species have been generally unsuccessful. The food chains of species targeted by the fisheries are relatively long, but short food chains seem to be an adaptation of lacustrine species. Because reservoirs with many piscivorous species sustain high fishery yields elsewhere in the world, the hypothesis that an excessive number of piscivores limits yields is not supported. Instead, inadequacies of fish assemblages in reservoirs of the Upper Paraná River basin appear to be symptomatic of an unsuitable environment for lacustrine fish species. The physical characteristics of reservoirs in the Upper Paraná River basin, exacerbated by climatic patterns, may preclude the emergence of successful reservoir species from within the extant pool of riverine species. The resulting assemblages have characteristics that are neither riverine nor lacustrine, and are maladapted to support fisheries in the reservoirs. The introduction of lacustrine species is destined to failure because environmental characteristics are not lacustrine, except in reservoirs positioned high in the watershed, where increased retention times allow lacustrine conditions. Published in 2001 by John Wiley & Sons, Ltd. 相似文献
2.
U. Asanka D. Jayasinghe Upali S. Amarasinghe Sena S. De Silva 《Lakes & Reservoirs: Research and Management》2005,10(3):157-166
This study was carried out to investigate the possibility of using the limnological characteristics of non‐perennial reservoirs in Sri Lanka for the future management of culture‐based fisheries. Forty‐five reservoirs were randomly selected to study their limnology, out of which 32 were stocked with fish fingerlings of Chinese and Indian carps, tilapia and freshwater prawn at stocking densities ranging from 218–4372 fingerlings ha?1. Of these, 23 reservoirs were harvested at the end of the culture period (6–10 months). Thirteen limnological parameters were measured during the water retention period of each of the 45 reservoirs between November 2001 and January 2004. The mean values of the limnological parameters were used to ordinate the reservoirs through principal component analysis. Ordination showed a productivity gradient among reservoirs where Secchi disc depth, total phosphorus, chlorophyll‐a, inorganic turbidity and organic turbidity were identified as key factors. The total fish yield of culture‐based fisheries was positively correlated to the scores of the first principal component axis. This study reveals that it is possible to classify non‐perennial reservoirs in Sri Lanka based on the above limnological parameters in order to develop culture‐based fisheries and that they could be applicable in comparable water bodies elsewhere in the tropics. 相似文献
3.
Implications of compensatory and additive mortality to the management of selected sportfish populations 总被引：3，自引：0，他引：3
The compensatory mortality hypothesis postulates that a population's total mortality remains unchanged at low to intermediate exploitation rates because natural mortality decreases to compensate for reduced density, whereas the additive mortality hypothesis postulates that any increase in exploitation mortality results in an increase in total mortality. Fishing and natural mortality rates have generally been assumed to be additive rather than compensatory. We reviewed mortality estimates for some prominent sportfish populations to identify evidence for compensatory or additive mortality. For largemouth bass Micropterus salmoides, total annual mortality increased with annual exploitation suggesting additive mortality. For crappies Pomoxis nigromaculatus and P. annularis, annual exploitation did not seem to affect annual mortality at low to moderate annual exploitation, but annual mortality increased with annual exploitation as it increased beyond 40%, conforming to the compensatory mortality hypothesis. Northern pike Esox lucius mortality estimates revealed no relation between annual mortality and annual exploitation, and highly variable annual mortality for a given annual exploitation. Evidence from the literature suggests that mortality of northern pike may be compensatory for fish smaller than 40 cm total length, but additive for larger fish. Because compensatory natural mortality reduces the managers’ability to control annual mortality, we suggest that further consideration of the compensatory mortality hypothesis be given to species that have shown variable mortality responses to reductions in annual exploitation. 相似文献
4.
Mesay Yami Alemayehu Wubie Abebe Cheffo Yared Mesfin 《Lakes & Reservoirs: Research and Management》2020,25(2):230-243
The present study was conducted to share the experience of promoting fish production and marketing from the Tendaho Reservoir of the Afar region, Ethiopia. The study results indicate the reservoir is serving its purpose, namely to generate gainful employment for the pastoralist youth and to create sustainable livelihoods and sources of income for the pastoralist‐fishermen of the Afar region. Further, the reservoir fish production has improved the nutrition and food security status of children. It also created a new business entry for hotels and restaurants in the area. Fishermen in the study areas, however, face problems getting the required support for such efforts, in the form of training in fish post‐harvest practices. The present study also indicates dried catfish marketing should be targeted in the short run to address the substantial fish spoilage observed in the high‐production hot season. Dried catfish marketing is highly recommended for the Afar region since it is well adapted to the climate of the study area, noting the product is less perishable and can be sold throughout the country. Dried catfish marketing is also expected to address the problem of gender inclusiveness, an issue clearly missing in the fish production system in the study areas. 相似文献
5.
Reservoirs constructed on floodplain rivers are unique because the upper reaches of the impoundment may include extensive floodplain environments. Moreover, reservoirs that experience large periodic water level fluctuations as part of their operational objectives seasonally inundate and dewater floodplains in their upper reaches, partly mimicking natural inundations of river floodplains. In four flood control reservoirs in Mississippi, USA, we explored the dynamics of connectivity between reservoirs and adjacent floodplains and the characteristics of fish assemblages that develop in reservoir floodplains relative to those that develop in reservoir bays. Although fish species richness in floodplains and bays were similar, species composition differed. Floodplains emphasized fish species largely associated with backwater shallow environments, often resistant to harsh environmental conditions. Conversely, dominant species in bays represented mainly generalists that benefit from the continuous connectivity between the bay and the main reservoir. Floodplains in the study reservoirs provided desirable vegetated habitats at lower water level elevations, earlier in the year, and more frequently than in bays. Inundating dense vegetation in bays requires raising reservoir water levels above the levels required to reach floodplains. Therefore, aside from promoting distinct fish assemblages within reservoirs and helping promote diversity in regulated rivers, reservoir floodplains are valued because they can provide suitable vegetated habitats for fish species at elevations below the normal pool, precluding the need to annually flood upland vegetation that would inevitably be impaired by regular flooding. Published 2013. This article is a U.S. Government work and is in the public domain in the USA. 相似文献
6.
While much is known about the fish assemblages, habitats, and ecology of rivers and reservoirs, there has been limited study of the fish assemblages in transitional habitats between these lotic and lentic habitats. Data about these river–reservoir interface (RRI) fish assemblages are needed to guide integrated management efforts of river–reservoir ecosystems. The aim of these efforts is to recommend flows for natural river function, conserve native riverine fish assemblages, and maintain reservoir sport fisheries. We used a multigear approach to assess the fish assemblages of four RRIs in the Colorado River Basin, Texas. In addition to characterizing RRI fish assemblages using species richness and evenness metrics, and habitat‐use guilds, we used a multivariate approach to evaluate intra‐annual shifts in species composition and abundance. All RRIs had high species richness and evenness values and included both macrohabitat generalist and fluvial species. RRIs also contained high proportions of the fish species available within each river–reservoir ecosystem, ranging from 55% to 80%. Observed intra‐annual shifts in RRI fish assemblages resulted from changes in abundance of dominant species rather than changes in species composition, with abundance of most species increasing from early spring to summer. Fish species responsible for intra‐annual shifts included mostly floodplain and migratory species, suggesting that species both used littoral habitats within RRIs and migrated through RRIs to river and reservoir habitats. The diversity of fishes found within RRIs highlights the importance of including these areas in future conservation and management efforts of river–reservoir ecosystems. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
7.
设置小型水库防逃设施是提高渔业经济效益的一项重要措施,但是防逃设施设置不规范将影响水库泄洪能力。为了规范小型水库渔业防逃设施建设与管理,分析了防逃设施建设对水库防洪的影响,研究防逃设施建设的合理范围,探讨小型水库渔业防逃设施运行管理要求。结果表明,考虑过流能力和最大过网流速设计的小型水库渔业防逃设施既能满足渔业生产要求,又能满足水库防洪要求。小型水库渔业防逃设施运行管理应明确责任、完善制度。 相似文献
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Many valleys in Western Australia have been dammed to provide irrigation and potable water. To minimize the risks of outlet blockages, basins have been cleared of vegetation and rocky outcrops during construction. As a result, dam basins contain limited numbers of aquatic habitats, being dominated by sandy and muddy substrata. Nonetheless, endemic crayfishes (especially marron, Cherax tenuimanus) and three introduced species of fishes support large recreational fisheries in irrigation reservoirs. Recently, it has been shown that Perca fluviatilis (red‐fin perch) imposes an extremely high mortality on C. tenuimanus in reservoirs, with the result that marron populations might be below reservoir‐carrying capacity. To test this hypothesis, three types of artificial habitats (pipes, tiles, mesh) that mimic natural habitat types were placed into a reservoir and their use by C. tenuimanus was assessed. As C. tenuimanus is an annual brooder, releasing young during November and December, the effects of artificial habitats on biomass concentration and productivity can be differentiated. The study results showed that C. tenuimanus rapidly populated artificial habitats (concentration effects). Small, newly recruited C. tenuimanus also utilized the pipe and tile habitats (productivity effects). The addition of these types of habitats increased the suitability of the reservoir for the studied C. tenuimanus population, increasing productivity, probably via reduction of teleost predation. The increased productivity of the C. tenuimanus population might, in turn, increase the productivity and sustainability of the recreational marron fishery. Other aquatic species, including a biofilm community, also utilized the artificial habitats, increasing the species richness in the dam. Due to the success of the current study, large artificial habitats have been installed into two irrigation reservoirs in order to increase recreational marron fishing and conservation values. 相似文献
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Kwadwo Kwarfo-Apegyah Patrick Kwabena Ofori-Danson 《Lakes & Reservoirs: Research and Management》2010,15(1):3-14
The spawning and recruitment patterns of the major Cichlid fish species, including Hemichromis fasciatus, Oreochromis niloticus, Sarotherodon galilaeus, Tilapia zillii and other species, Auchenoglanis occidentalis, Brycinus nurse, Clarias gariepinus and Marcusenius senegalensis were studied for 24 months in Bontanga Reservoir, Ghana, using length‐based fish stock assessment approaches. The species spawned throughout the year, with two spawning pulses described as major and minor spawning seasons. The major spawning season occurred from March to September for the Cichlids, and from May to September for the other species. The minor spawning season, indicative of extended spawning, occurred from October to March for all the fish stocks. Fish spawning began with the onset of the rains in April/May, peaking by June/July, before the rainfall peak in August for all the fish stocks studied. Recruitment was found to occur throughout the year, with major and minor pulses coinciding with the major and minor spawning seasons. Accordingly, the most appropriate time for a possible closed fishing period appears to be from June to August, 1 month after the start of, and before the end of, the rains. The estimated mean standard length (Lm) for first time spawners of A. occidentalis, B. nurse, C. gariepinus and H. faciatus were 11.7, 12.7, 2.7 and 7.5 cm respectively. The estimated maturity–length ratio of 0.4 and 0.2 for O. niloticus, S. galilaeus and T. zillii were lower than the known 0.7 for normal growth, suggesting the tilapias matured faster, and at a smaller size, in the reservoir. Apparent sexual precocity associated with early maturity, year‐round spawning and recruitment were some important adaptations found to have sustained the reservoir fisheries, even during high fishing pressures. For conservation and sustainable exploitation of the fisheries, instituting a closed fishing season, mesh size regulations, withdrawal rights and a community‐based fishery management system are recommended. 相似文献
12.
Afua Adwubi Bright Kofi Amegashie Wilson Agyei Agyare Lulseged Tamene Samuel Nii Odai Charles Quansah Paul Vlek 《Lakes & Reservoirs: Research and Management》2009,14(4):279-287
Many small dams and dugouts have been constructed in the Upper East Region of Ghana to address the problem of regional water scarcity. The reservoirs were constructed primarily as water supplies for agricultural irrigation and livestock watering, aquaculture and domestic use. However, many of the reservoirs dry up during the dry season, affecting the livelihoods of their basin inhabitants. A major cause for the dried reservoirs is siltation, which reduces the reservoir’s storage capacities. The goal of this study is to quantify the annual siltation rate of four study reservoirs, using a bathymetric survey and reservoir soil sampling. The sediment yield and its relation to catchment area also were assessed. The results of this study indicate that the annual siltation rates are 1272, 3518, 2764 and 6135 t year?1 for Doba, Dua, Zebilla and Kumpalgogo reservoirs, respectively. Analyses of the sediment yield and catchment areas illustrated that the sediment yields decreased with increasing catchment area. All the study reservoirs have lost their dead storage capacity, which was meant to store sediment until the end of their anticipated design lives. The decreasing storage capacity because of siltation will affect the livelihoods of the local basin inhabitants, as the reservoirs will not be able to achieve all their intended purposes. The results of this study indicate that, because siltation is not the only factor threatening the benefits gained from the reservoirs, the integrated assessment of all relevant factors is required. 相似文献
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Mirtha A. Angulo‐Valencia Angelo A. Agostinho Harumi I. Suzuki Karla D. G. da Luz‐Agostinho Carlos S. Agostinho 《Lakes & Reservoirs: Research and Management》2016,21(4):362-374
Major changes to local river habitats, after impoundment, are expected to restrict the reproductive activity of fishes with migratory strategies, although the changes are not expected to have relevant effects on fishes with other strategies. The reproductive activity of fishes with different reproductive strategies was evaluated along a longitudinal gradient before, and after, the formation of a reservoir on the Tocantins River (Tocantins State, Brazil). Samples were collected at six sites distributed along 80‐km stretch of the reservoir (R1 to R6 in the upstream–downstream direction) before and after the impoundment. The highest mean values of the reproductive activity index (RAI), considering all species in the river phase, were recorded for the intermediate segments (R4). The reproductive activity was classified as intense at the two sites located further upstream (R2 and R1). The highest mean RAI value after impoundment was observed for the site further upstream (R1). The reproductive activity was classified as intense, however, at every site, except for R6. Regardless of the reproductive strategy, mean RAI values were higher in this phase at site R1, particularly for long‐distance migratory species (LDM). The most lacustrine area (R6) was only relevant for the group of species with parental care. For non‐long‐distance migratory species, without parental care, the reproductive activity was intense at every site, except for R6. Overall, after the impoundment, the fish species tended to seek more lotic environments to spawn, including the riverine zone of the reservoir and side tributaries, regardless of the reproductive strategy. The results of this study provide evidence that impoundments affect the reproduction of the fish, independent of the reproductive strategy, although the intensity of the effect is different for each group. 相似文献
15.
地表糙度是影响坡面侵蚀产沙的重要因素之一,以往研究多关注糙度对坡面产流产沙特征的影响,而较少关注不同糙度条件下坡面微地形变化和侵蚀产沙的关系。通过人工模拟降雨试验,结合Photoscan技术研究了不同雨强和地表糙度对坡面微地形及产流产沙的影响。结果表明:在试验条件下,降雨后光滑坡面和粗糙坡面4个微地形因子(地表糙度、地形起伏度、地表切割度、洼地蓄积量)数值均减小,且有随雨强增大,其减幅增大的趋势;相同雨强和降雨历时条件下,粗糙坡面微地形因子变化幅度大于光滑坡面,微地形因子变化量与侵蚀产沙量呈明显正相关;与光滑地表相比,粗糙地表只在降雨初期能有效减少产流,随着降雨时间延长,2种坡面的产流率趋于一致;在试验选取的4个雨强条件下,粗糙坡面和光滑坡面产流率均呈现先增大后趋于稳定的趋势。粗糙坡面产沙率和产流率变化规律一致,但光滑坡面产沙率表现出在产流初期迅速增大,而后呈降低并趋于稳定的趋势。研究结果可为揭示坡面土壤侵蚀机理和建立坡面侵蚀产沙模型提供参考。 相似文献
16.
Fish community surveys were conducted in five tributaries of the Corumbá River before and after damming. Electrofishing samples were collected monthly in the pre‐impoundment period (March 1996 to August 1996) and 15 in the post‐impoundment period (September 1996 to February 1999). A self‐organizing map (SOM, an Artificial Neural Network algorithm) was used to represent the patterns of fish assemblages. Samples collected in both the pre‐ and post‐impoundment periods were randomly dispersed on the SOM, and, therefore, a clear and significant pattern of separation between samples collected during these two time periods was not found. Mean and maximum water depth, which is correlated with ground water level, did not significantly separate the pre‐ and post‐impoundment samples. However, we found significant differences between the two periods for water temperature, pH, conductivity, DO and current velocity, but abundances of fish species (summarized in the clusters identified by the SOM) did not differ significantly. Instead, the validity of the clusters distinguished by the SOM was confirmed by significant differences in some biotic variables: species richness, equitability and log transformed total abundance. Indicator species values identified the most preferred cluster (and respective complex of environmental factors) for a given species. Only one cluster did not contain any significant species indicator values, but it was dominated by samples from the Furnas Stream, which was the only effluent that could be entered by fish from the main river channel after the damming owing to its location below the dam, which has no fish ladder. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
17.
Reservoirs are important components of modern aquatic ecosystems that have negative impacts on native aquatic biota both up‐ and downstream. We used a landscape‐scale geographic information system (GIS) approach to quantify the spatial effects of 19 large reservoirs on upstream prairie fish assemblages at 219 sites in Kansas, USA. We hypothesized that fish assemblage structure would vary with increasing distance from a reservoir and that the abundance of reservoir fishes in upstream reaches would decline with distance from a reservoir. Ordination of sample sites showed variation in fish assemblage structure occurred primarily across river basins and with stream size. Variance partitioning of a canonical ordination revealed that the pure effect of reservoir distance explained a small but significant (6%; F = 4.90, P = 0.002) amount of variability in fish assemblage structure in upstream reaches. Moreover, reservoir species catch per unit of effort (CPUE) significantly declined with distance from a reservoir, but only in fourth‐ and fifth‐ order streams (r2 = 0.32, P < 0.001 and r2 = 0.49, P < 0.001, respectively). Finally, a multivariate regression model including measures of stream size, catchment area, river basin, and reservoir distance successfully predicted CPUE of reservoir species at sites upstream of Kansas reservoirs (R2 = 0.45, P < 0.001). Overall, we found significant upstream effects of reservoirs on Kansas stream fish assemblages, which over time has led to a general homogenization of fish assemblages because of species introductions and extirpations. However, characteristic reservoir species are present throughout these systems and the importance of spatial proximity to reservoirs is probably dependent on the availability of suitable habitat (e.g. deep pools) in these tributary streams. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
18.
以2013年9月~2014年12月从鄱阳湖、赣江以及长江采集的234尾鲢鱼为样本,对当地鲢鱼的生长特点进行了研究,以分析各江段鲢鱼资源。采集到的鲢鱼体长范围为120.0~780.0 mm,体量范围为31.1~9 278.5 g。采用Key公式拟合了鲢鱼体长与体重的关系,发现鲢鱼质量与体长呈明显的幂函数关系,表明该江段白鲢为匀速生长类型。用Von Bertalanffy方程对鲢鱼的生长速度进行了拟合,发现鲢鱼群体的生长拐点为5.6龄,拐点体长64.1 cm,拐点体重5 139.7 g,说明当5.6龄白鲢是该江段最佳的捕捞年龄。与其它江段相比,鄱阳湖、赣江以及长江白鲢的生长性能和年龄结构表现出一定的衰退趋势,因此,应从加强渔政管、设立禁渔期、合理控制网箱养鱼以及建立保护区等方面对白鲢资源进行保护。 相似文献
19.
Éder A. Gubiani Luiz C. Gomes Angelo A. Agostinho 《Lakes & Reservoirs: Research and Management》2009,14(4):289-299
Length–length and length–weight relationships was estimated for 48 fish species collected in 30 neotropical reservoirs located in the State of Paraná, Brazil. Significant relations were found for all species. The values of the parameter slope (b) in the length–weight relationship ranged from 2.49 to 3.46 for grouped sexes, and from 2.66 to 3.15 for separated sexes. Differences between sexes (indication of sexual dimorphism) were verified for 20 species. Males exhibited greater lengths than females for Astyanax janeiroensis, Bryconamericus iheringii, Geophagus brasiliensis, Glanidium ribeiroi and Hypostomus derbyi, whereas females attained greater lengths than males for the other 15 species examined in this study. 相似文献
20.
阐述了巴基斯坦电力市场电力系统分布、装机容量、电力供需缺口、水电资源分布等方面情况,给出了中国水电设备制造和建筑施工企业开发巴基斯坦水电市场的建议。 相似文献