Ascent of neotropical migratory fish in the Itaipu Reservoir fish pass

The Piracema Canal is a complex 10‐km fish pass system that climbs 120 m to connect the Paraná River to the Itaipu Reservoir along the Brazil–Paraguay border. The canal was constructed to allow migratory fishes to reach suitable habitats for reproduction and feeding in tributaries upstream from the reservoir. The Piracema Canal attracted 17 of the 19 long‐distance migratory species that have been recorded in the Paraná River Basin and Paraguay–Paraná Basin. However, the incidence of migratory fish decreased from downstream to upstream, with the pattern of decrease depending on species. Overall, 0.5% of the migratory fish that entered the Piracema Canal and segment 1, eventually were able to reach segment 5 and potentially Itaipu Reservoir. Ascension rate was examined relative to various physical attributes of canal segments; maximum water velocity emerged as the most influential variable affecting fish passage. Water velocity may be manipulated by controlling water discharge, and by re‐engineering critical sections of the canal. Because the Itaipu Reservoir flooded a set of falls that separated two distinct biogeographical regions, facilitating fish movements through the Piracema Canal into the Itaipu Reservoir presents a management dilemma that requires deliberation in the context of the fish assemblages rather than on selected migratory species. Copyright © 2010 John Wiley & Sons, Ltd.     

Trophic state, fish community and intensive production of salmonids in Alicura Reservoir (Patagonia, Argentina)

The Governments of the Provinces located in Patagonia, Argentina, promote the intensive breeding of salmonids in the Andean Patagonian region. Although annual production is low (450 ton ha^–1 year^–1), some effects are significant. Waste produced by salmonid breeding (feed losses, faeces and excretion) increases nutrient and organic matter concentrations, which cause modifications of water quality, sediments and biota. A consequent risk is the elevation of eutrophication levels. Possible changes in water composition, sediments, algae and wild fish populations were studied. Sites affected by fish farming showed increased nutrient concentration, and phytoplankton and periphyton biomass. Chlorophyll a was similar at both sites (affected and unaffected by fish farm sites). Sediments clearly reflect fish farm waste inputs: total phosphorus and organic matter increased 12‐fold and fourfold, respectively. The species present in the gill‐net catches were the autochthonous Percichthys trucha, Odontesthes hatcheri, Diplomystes viedmensis, and the introduced salmonids Oncorhynchus mykiss, Salmo trutta, Salmo salar sebago and Salvelinus fontinalis. About 50% of the total catch was salmonids. A major portion of the catch per unit weight was composed of rainbow trout, followed by perch. The catch per unit weight obtained for this reservoir agrees with the range of values previously determined ( Quiros 1990 ) for Patagonian reservoirs. Compared with previous studies by Freyre et al. (1991) , a variation in catch composition exists. This consists mainly of an increase in the numbers and condition of O. mykiss and a decrease in P. trucha. Presence of fish that escaped from hatcheries, recognizable by their eroded fins, was observed; particularly in a sampling station near the fish cage systems. Variations in catches could be caused by cyclical changes in fish populations ( Wooton 1991 ), by direct and indirect effects of intensive fish farming, or by a combination of both events, and can only be understood through long‐term studies of catch variation.     

Comparison of different predictive models for estimating fish yields in Shahpur Dam,Pakistan

Water reservoirs and dams are major water resources, being diverse in terms of both size and fisheries potential. Reservoir productivity is variable, with significant variations being observed for reservoirs of comparable size and geology, even within the same geographical area. The ability to estimate fish yields through the application of predictive models is an important step for the effective management of fisheries resources in freshwater basins and flowing waters. Various physical, chemical and biological processes establish limits on the yield of commercial fish species. Various physicochemical parameters were measured in this present study during 2001–2002 on a monthly basis for Shahpur Dam in Pakistan. Morphoedaphic indices were derived as MEIt, MEIc and MEIa. A number of different predictive models proposed for different regions are used to predict fish production in Shahpur Dam, for comparison with the actual fish production. From a management perspective, fish yield predictive models based on MEI appeared to be most useful as fish yield predictors.     

小浪底水库排沙对下游鱼类的影响研究

采用现场调查和室内实验相结合的方法研究了黄河小浪底水库排沙期间下游河流出现鱼类死亡现象的原因。2010年度小浪底水库排沙期间,下游出现了高含沙水流过程,伴随出现了鱼类死亡现象,调查发现受影响鱼类有5目5科11种。水库排沙期间的含沙量、溶解氧变化过程的现场调查及室内实验结果表明,小浪底水库排沙时细颗粒泥沙含量较高,堵塞和损坏鱼鳃是导致鱼类死亡的原因之一。当含沙量大于80kg/m3时,水体溶解氧下降至鱼类生存所需下限2mg/L以下,鱼类在短时间内缺氧而死亡;当含沙量低于60kg/m3时,根据现场调查结果及相关人员经验判断水库下游河道内不会出现鱼类死亡漂移现象。水库排沙期间,下游河道水体的含沙量与溶解氧浓度具有较好的相关性,即河道水体的溶解氧浓度随着含沙量的增加而减少,可通过控制出库含沙量及其持续时间减轻水库排沙对鱼类的影响。     

Riverine characteristics dictate composition of fish assemblages and limit fisheries in reservoirs of the upper Paraná River basin

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.     

Migratory fishes of Brazil: Life history and fish passage needs

Many of the most important commercial and recreational species of the megadiverse Brazilian freshwater fishes migrate in rivers among essential habitats during all life stages. These movements, however, have been severely blocked by hundreds of hydroelectric dams and reservoirs and they will be even more obstructed due to hundreds of new developments. Fishways have been used in many countries to allow fish to pass around dams. Fishway construction is booming in Brazil, but poor understanding of migrations by Brazilian fishes has led legislators, scientists, and the public to several misconceptions about the rules of fishways in fisheries conservation. First, is a belief that fishways are only needed to facilitate upstream spawning migrations. Also, it has been suggested that upstream passage for Neotropical migrant fishes is not useful if there is no large free‐flowing stretch upstream of a dam that contains spawning habitat and has a large natural floodplain (nursery habitat). In this paper, we discuss that, in addition to providing passage for pre‐spawning migrants, upstream fishways also provide passage for other fish migrations (e.g. foraging), and that all up‐ and downstream migrations during life history need to be addressed at dams to conserve fish resources. We also argue that an upstream fishway is important even if the upstream reach does not have spawning or nursery habitats. In addition, we discuss the need for protection of downstream migrant fish, and the importance of fish behaviourists and engineers working together on fishway design and operation to solve fish passage issues. Copyright © 2008 John Wiley & Sons, Ltd.     

Spawning and recruitment patterns of major fish species in Bontanga Reservoir, Ghana, West Africa

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 (L_m) 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.     

Spatial effects of reservoirs on fish assemblages in Great Plains streams in Kansas,USA

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.     

Habitat diversity and fish assemblage structure in local river widenings: A case study on a swiss river

We investigated habitat availability and fish assemblage structure in three local river widenings, completed 3–14 years ago, and five adjacent canalized reaches on the river Thur, a seventh‐order river in Switzerland. To account for seasonal variability, surveys were repeated in winter and summer 2005. Results were compared with historical pre‐disturbance data to evaluate whether the current abiotic and biotic conditions in the study reaches have attained historic near‐natural levels. Hydro‐physical habitat diversity (depth, flow velocity, cover availability) was considerably greater in the two longer widenings (>900 m length) than in the canalized reaches and in the shortest widening (300 m length), with higher proportions of shallow or deep areas of different flow velocities. However, the comparison of current and historical near‐natural shoreline lengths indicated that the current geomorphological complexity is still considerably impaired in all reaches. No overall significant relationship was found between the reach type (canalized or rehabilitated) and the number of species or the total fish abundance which were strongly correlated with the availability of suitable cover and moderate flow velocity. However, highest winter abundances were observed in deep, well‐structured backwaters of the rehabilitated reaches, documenting their significance as wintering habitats. Assemblage structure and composition were similar in canalized and rehabilitated reaches. Compared to the historical data, however, fewer and different dominant species were found, and guild composition changed towards a higher representation of generalists and tolerant species. Copyright © 2008 John Wiley & Sons, Ltd.     

考虑鱼类繁衍需求的三峡水库汛期调度要求及可行性探讨

长江中下游鱼卵数量急剧减少,鱼类繁衍期推迟。针对鱼类繁衍需求,本文通过总结鱼类繁衍条件,提出鱼类繁衍期三峡水库泄流要求及生态调度方案,并计算分析历史径流满足生态调度方案的程度;通过建立繁衍前期和繁衍期来流关联,提出天然径流不满足情况下的预蓄调度方案并探讨其可行性。结果表明:2004-2013年三峡水库入库径流满足生态调度方案的程度较低,需采取预蓄水量措施;在实际入库径流情况下,预蓄水位范围为145.00~159.34 m;在80%概率入库径流下,预蓄水位范围为145.00~156.63 m。如按80%概率的入库径流预蓄水量,当预报预泄期为7天时,预蓄调度方案不会增加三峡水库的防洪风险。     

Length–length and length–weight relationships for 48 fish species from reservoirs of the Paraná State,Brazil

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.     

江边水电站鱼类增殖站建设与管理

文章重点介绍江边水电站鱼类增殖站的建设情况及运行管理。该工程作为九龙河流域5个梯级电站中唯一的一座鱼类增殖站,其建设将为减轻流域水电开发对水生生态造成的影响作出重要贡献。     

Studies on the fish catch efficiency of different types of fishing gear in Kaptai Reservoir, Bangladesh

A comprehensive analysis of the efficiency of different fishing gear in capturing Cyprinidae (major carp) species in Kaptai Reservoir, Bangladesh, was conducted. The catch per unit effort (CPUE) data were collected during a 1‐year survey, covering a total of 493 independent fishing units spread across the four major fishing grounds of the reservoir. The study examines the CPUE and catch composition between months and study sites, and the effects of reservoir water level fluctuations, gear diversity and fish distribution patterns on the fish catches. The mean CPUE for all gear ranged between 2.91 and 30.86 kg unit^?1 day^?1. Analysis of variance showed significant differences among the fishing gear types. The CPUE differed significantly between months for lift nets, large‐meshed (LM) gill nets, cluster hooks and hand lines. None of the fishing gear exhibited significant differences between sites except for cluster hooks. The CPUE of small‐meshed (SM) seine nets was significantly higher than that of other gear. The reasons for such differences in the fish catches were identified as the choice of fishing places, the net sizes, the number of hooks, lures and baits, water turbidity, wind, waves and rainfall. The CPUE indices for lift nets showed significant variation between months for the Cyprinidae species. A significant variation in catch at the different sites was found for all nets, except SM seine nets. The contribution of the Cyprinidae species showed significant differences between sites only for hand lines. The coefficient of variation of CPUE for fishing nets did not vary much more than 55% (lift net), whereas the highest variation of 49% was recorded for hand lines among the hooks and line. Higher reservoir water levels were followed by reduced CPUEs for the Cyprinidae species and vice versa, whereas the highest water levels corresponded to the higher CPUE for the Clupeidae species.     

下游梯级河川式水库冲淤计算与预测

本文考虑到下游梯级水库形态的变化同时受到上游梯级水库和其自身水库调蓄运用的影响,提出下游梯级河川式水库冲淤计算的方法。后经紫兰坝水库河工模型验证,表明该法精度良好,计算结果与实验比较一致。     

Movement of three non‐salmonid fish species through a low‐gradient vertical‐slot fishway

Well‐designed fishways have assisted in restoring migrations and rehabilitating riverine fish species in all continents. The performance of fishways varies greatly with their type, design and operating regime, and with the species involved. Vertical‐slot fishways are widely used to overcome low‐level barriers, especially for non‐salmonids. Important issues remain in the design of fishways to meet performance and cost criteria, including the relationship between fishway bed gradient and the fish that ascend, and whether resting pools are needed. Models of species' movement patterns can inform fishway designers about likely fish response to various design options, and can lead to improved efficiency and effectiveness. Models of general movement patterns of three potamodromous non‐salmonid fishes in the Murray River, Australia, were developed from empirical data in a low‐gradient vertical‐slot fishway. The models integrate data on times of entry and exit, ascent rates, and whether fish continued to ascend during the night. These fish species did not favour resting pools. Ascent rates of fish ≥120 mm were more closely related to fish behaviour than to length; for a given fishway height, reducing bed slope by increasing the number of pools may slow the ascent of such fish, whereas enlarging pool volumes increases costs. Copyright © 2010 John Wiley & Sons, Ltd.     

梯级水库的联合防洪调度及防洪风险分析

由于我国兴建的水库大坝约90%为土坝,有相当部分为梯级水库,当水库遭遇突发事件如超标准洪水、地震、地质灾害问题造成的坝体坍塌、大坝渗漏发生管涌等工程事故、战争或恐怖事件等因素导致溃坝,将使蓄量巨大的洪水瞬间向下游倾泻,引发严重的洪涝灾害,对人民生命财产安全和社会经济发展造成严重威胁和破坏。由于梯级水库建于同一条河道上,当上游水库大坝突遇险情溃坝时,会引起下游水库溃坝的连锁反应,这样造成的灾害特别巨大。因此研究梯级水库联合防洪调度措施,并对其进行防洪风险分析,寻找最优的调度方式,最大可能降低甚至避免大坝溃坝风险,这对保证当地人民群众的生命财产安全和社会经济的可持续发展具有重要的意义。     

Declining commercial fish catches in Lake Victoria's Winam Gulf: The importance of restructuring Kenya's aquaculture programme

The total weight of commercial fish (metric tons) caught in the Winam Gulf area of Lake Victoria in Kenya declined from 3300 mt to 760 mt between 1995 and 2009. Associated with this decline, and ranked in descending order, the species richness of the commercial fish catch was limited to seven major groups (Rastrineobola argentea; Lates niloticus; Protopterus aethiopicus; Labeo victorianus; Haplochromis species; Clarias gariaepinus; Bagrus domac). Numerous hypotheses ranging from eutrophication, inadequate control of the exotic water hyacinth and overfishing were advanced to explain this decline. The Kenyan government, working in partnership with international organizations, implemented multiple restoration and management programmes in response, including aquaculture. Unfortunately, success for this implemented programme has been very limited because important socio‐economic driving factors were overlooked. To provide a better understanding of the issues, 150 members of the Winam Gulf fishing community, ranging in age from 20 to 40 years, were surveyed. The results of this survey identified poverty and inadequate education as two major issues requiring substantial attention. The survey also suggested that if societal changes are to occur, it will rest upon changing the beliefs of the youth in the Winam Gulf area. Restructuring Kenya's aquaculture programme, with a focus on the youth, provides a pathway for increasing the literacy level of the community, as well as for reducing poverty.     

梯级水库调度系统及其在三峡初期蓄水中的应用

三峡水库于2003年6月成功地完成了初期蓄水任务，作为其自动化技术支撑平台的三峡梯级水库调度自动化系统在实际应用中发挥了重要作用。该系统在规划、设计和建设上使用了诸多先进的技术手段，系统规模和设计水平在国内处于领先地位。