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1.
Low‐head dams are ubiquitous in eastern North America, and small dam removal projects seek to improve habitat conditions for resident and migratory fishes. Effects of small dams of varying status on local fish communities are poorly documented, and recent work suggests benefits of maintaining fragmentation. We sampled fish at 25 dams (9 breached, 7 relict, 9 intact) in three river basins in North Carolina, USA. Fishes were sampled at three reaches/dam from 2010 to 2011. Study reaches were located upstream (free‐flowing reaches), downstream (tailrace) and >500 m downstream of dams (n = 75 reaches). Analyses revealed significantly elevated fish CPUE, taxa richness and percentage intolerant taxa in intact dam tailraces suggesting small dams may improve conditions for resident taxa. Breached dam tailrace reaches exhibited lower fish CPUE, taxa richness and percentage intolerant taxa relative to upstream reference reaches. Relict dams exhibited no between‐reach differences in fish community metrics. Nonmetric multidimensional scaling revealed drainage‐specific stream fish responses across study drainages. Tar and Roanoke drainage streams with intact and relict dams supported fish assemblages indicative of natural communities, whereas Neuse Drainage streams with intact and breached dams contained disturbed habitats and communities. These data demonstrate fish community responses to dam condition are drainage specific but communities in streams with intact and relict dams are largely similar. Additionally, breached dams may warrant higher removal priorities than intact dams because they negatively influence fish communities. The variability in response to some dams indicates managers, regardless of region or country, should consider holistic approaches to dam removals on a case‐by‐case basis.  相似文献   

2.
We employed the trophic upsurge hypothesis as an analytical framework to describe the response of Neotropical fish communities to terrestrial inundation associated with river damming. Data were collected for the impact assessment of the Peixe Angical Dam, Tocantins River, Brazil. Monthly surveys were conducted at nine sites (seven upstream, two downstream) from 15 months before to 20 months after dam closure and a follow-up survey 60–83 months after closure. Fish responses differed in timing and magnitude across sites. In the new reservoir, populations peaked 8–13 months after flooding, demonstrating increases in richness (84 ± 52%), biomass (329 ± 266%) and abundance (681 ± 348%) with the maxima for richness and abundance tending to precede biomass maxima. Populations of all families increased but were greatest for Engraulidae, Hemiodontidae, Serrasalmidae and Characidae, and lower for the benthic catfish: Sciaenidae, Dorididae, Pimelodidae. Downstream populations peaked 5–12 months after closure or showed consistent decline. Five years after dam-closure richness and abundance were lower compared to predam levels, with populations at all sites demonstrating an ongoing decline. Reservoir creation triggers reproductive recruitment and otherwise pools spatially disparate populations from across the flooded valley. If the rise in richness is largely explained by the increased catchability of species otherwise present prior to flooding, it may be more appropriate to estimate species loss with reference to upsurge data. As peak biomass coincides with declining richness, modelling fisheries production from annually aggregated data may risk overestimating the potential for sustainable harvests. Upsurge–response curves can help identify the timing of critical ecological thresholds for flood-managed fisheries.  相似文献   

3.
Hydroacoustic surveys were conducted to understand the relationship between fish density, spatial distribution, and behavior upstream and downstream of the Changzhou Dam on the Pearl River, China, and the condition (open/closed) of the spillways. When the spillways were open on 24 June 2010, numerous fish were observed to be densely distributed in the forebay upstream of the dam, with an average fish density was 0.22 fish m−3. When the spillways were closed on 25 June 2010, the fish upstream of the dam dispersed, and the average fish density decreased to 0.007 fish m−3. Prior to operating the spillways on 24 May 2010, the average fish density downstream of the dam was 0.28 fish m−3; in comparison, on 26 June, immediately following closure of the spillways, the average fish density downstream of the dam was 0.08 fish m−3. Fish were more active on June 24 than on 25 June: they swam faster and their positions in the water column varied greatly. On 26 June, fish did not to swim as freely in the water column as those measured on 24 May. Based on these observations, we conclude that a large number of fish are able to swim to the upstream side of the dam while the spillways are open.  相似文献   

4.

5.
We studied the trait diversity and structure in the fish communities of two floodplain lakes of the Caura River: Aricagua and Paramuto, during one hydrological cycle. We calculated taxonomic and a functional alpha and beta diversities and made comparisons among hydrological seasons and among habitats within each lake based on rarefactions. The trait structure was explored with an RLQ (analysis of a table R of environmental conditions, a table L of abundances of species and a table Q of species traits) analysis, and pairwise relationships between environmental variables and traits were explored with fourth‐corner analyses. Despite its smaller extension, Paramuto showed higher alpha taxonomic and trait diversities. The substrates of open sand and those covered by leaf litter were the most diverse habitats in terms of both species and traits. The trait structure of the fish communities was influenced by the hydrological seasons, the lakes as well as water pH and temperature, and in a lesser degree dissolved oxygen, habitat type and total dissolved solids in the water. These factors constitute the habitat templet for the fish community's composition and trait structure.  相似文献   

6.
Passage of fish through hydropower dams is associated with mortality, delay, increased energy expenditure and migratory failure for migrating fish and the need for remedial measures for both upstream and downstream migration is widely recognised. A functional fish passage must ensure safe and timely passage routes that a substantial portion of migrating fish will use. Passage solutions must address not only the number or percentage of fish that successfully pass a barrier, but also the time it takes to pass. Here, we used radiotelemetry to study the functionality of a fish bypass for downstream‐migrating wild‐caught and hatchery‐released Atlantic salmon smolts. We used time‐to‐event analysis to model the influence of fish characteristics and environmental variables on the rates of a series of events associated with dam passage. Among the modelled events were approach rate to the bypass entry zone, retention rates in both the forebay and the entry zone and passage rates. Despite repeated attempts, only 65% of the tagged fish present in the forebay passed the dam. Fish passed via the bypass (33%), via spill (18%) and via turbines (15%). Discharge was positively related to approach, passage and retention rates. We did not detect any differences between wild and hatchery fish. Even though individual fish visited the forebay and the entry zone on multiple occasions, most fish passed during the first exposures to these zones. This study underscores the importance of timeliness to passage success and the usefulness of time‐to‐event analysis for understanding factors governing passage performance.  相似文献   

7.
Abstract – In this study, we investigated how taxonomic and functional diversity of fish communities is influenced by forest cover and mesohabitat types in Neotropical lowland streams. We sampled fish fauna of 126 five‐metre‐long mesohabitats using an electrofishing unit in forested (n = 3) and deforested (n = 3) streams in the upper Paraná River basin, south‐eastern Brazil. According to velocity and depth, three mesohabitat types have been considered: riffles (shallow and fast‐flowing habitat), pools (deep and slow‐flowing habitat) and runs (intermediate depth and velocity). Seven functional traits and 27 trait categories related to ecological, behavioural and life‐history aspects of fish were considered. Our results indicate that forest cover and mesohabitat type influence fish communities in different ways. Whereas deforestation affects communities primarily through changes in diversity (functional and taxonomic), mesohabitat types determine changes in the functional composition. The increased diversity in deforested mesohabitats is driven by a decrease in species turnover among habitat patches within streams. This can be attributed to new feeding opportunities and microhabitat availabilities in deforested streams so favours the occurrence of species having a particular set of traits, indicating a strong habitat–trait relationship.  相似文献   

8.
Impoundments caused by dams are often responsible for intense changes in physical, chemical, geomorphological and hydrological characteristics of rivers, and are one of the main causes in global freshwater biodiversity declines. When these changes derive from multiple cascading dams, the cumulative effect can amplify, causing more pronounced consequences than each individual reservoir, which may affect, among other factors, the biotic and functional conditions of fish fauna. We aim to evaluate the impact of dam cascades on fish functional diversity by applying trait-based analysis. We evaluate the functional attributes (functional indices and community-weighted means of trait values) and environmental variables at 11 sites, which encompassed different segments affected by the hydroelectric plants (transition, reservoir, reduced discharge section and tributary) in the Antas River Basin dam cascade system located in southern Brazil. The spatial differences of the functional indices (richness, evenness, divergence, dispersion and diversity) as well as the weighted averages of each functional trait were tested through analysis of variance. The most affected functional characteristics were those related to habitat exploration by detritivorous species, especially the use of food resources and body shape, as well as the type of swimming movement. These traits were more representative at the most downstream site of the complex. Thus, our results suggest that the cascade of dams acts in the functional homogenisation of the ichthyofauna in the intermediate stretches, mainly reflecting physical changes in habitat.  相似文献   

9.
Hydropower structures hinder the movement and migration of fishes, impairing their life cycles. Additionally, downstream moving fish are often at risk of being injured during turbine passage. To improve hydropower production towards more fish-friendly techniques and management, knowledge on timing and extent of natural patterns of fish downstream movement is necessary. So far, migration behaviour of long-distance migrators such as eel or salmon has been well studied, but little is known about seasonal and diurnal movement patterns of nonmigratory species or medium-distance migrators. In this study, movement patterns of 39 fish species captured by stownets while transiting hydropower facilities in four impounded rivers were assessed and compared with the fish community composition directly upstream of the hydropower plants assessed by electrofishing. Strong differences between the fish community composition inhabiting the upstream sides of the dams and the fish detected in downstream passage were evident. In each study river, the downstream moving fish community composition differed significantly between spring and autumn. On average, significantly more fish were caught during the night (2.9 fish/hr) than during the day (1.3 fish/hr). Topmouth gudgeon, European grayling and pike-perch mostly moved downstream during the night, whereas roach, spirlin and bleak were the most frequent downstream moving fish during daytime. Downstream fish movement was positively related with turbidity, water temperature and discharge. The strong differences in seasonal and diurnal fish movement patterns suggest that fish damage can be strongly reduced by adaptive turbine and corridor management, for example by shutting down turbines at peak movements.  相似文献   

10.
Behavioural tracking of endangered adult Sakhalin taimen (Parahucho perryi) by acoustic telemetry was conducted in the Bekanbeushi River system that flows through eastern Hokkaido in 2008–2010. A total of 39 tracked P. perryi showed extensive use of the river system, both upstream and downstream, regardless of the month or year. No tracked adult P. perryi stayed in the ocean for more than 1 day. Some of the fish (20%) dwelled in upstream habitat consistently from spring to autumn, while 40% of individuals showed wide utilisation of the entire upstream and downstream systems. Although 39.4% of tracked fish utilised two or more primary tributaries to the main river, 6.1% used only the main river system. Distinct variability was observed between individuals based on the proportion of time spent in each stream reach (up‐, mid‐, and downstream). A trend was observed in 2008 and 2010 showing that tracked fish moved to the upper stream reaches when water temperatures downstream increased. This trend was not observed in 2009 when the summer water temperature downstream was more than 2 °C below average when compared to 2008 and 2010. Our results suggest that adult P. perryi in the Bekanbeushi River system exhibit high behavioural plasticity, that is, the fish can select habitats based on their own individual requirements. Our results also demonstrate the importance of physical continuity among river reaches both upstream and downstream such that P. perryi does not experience barriers in moving to optimal habitats.  相似文献   

11.
Dams across the Great Lakes basin are nearing or beyond their original design life, posing both challenges and opportunities to natural resource managers. Ageing dams can be repaired to preserve function and maintain safety, removed to promote full connectivity or retrofitted with a fish passage structure to increase connectivity without reservoir loss. The success of rock ramp structures is not well documented, especially for cool‐ and warm‐water fishes in the Great Lakes basin. The success of a recently built (2009) rock ramp for increasing upstream fish passage on the Shiawassee River in Michigan, USA, was evaluated. While there was evidence of limited fish passage during the study period (2011–2016), catches of spring migratory fishes, fish eggs and larvae were significantly higher below the rock ramp than above, indicating the dam with rock ramp fish pass continues to limit upstream migration. Overall connectivity appears improved relative to a reference, dammed river, but falls short of full connectivity.  相似文献   

12.
  • 1. Costa Rica has recently experienced a rapid proliferation of dams for hydropower on rivers draining its northern Caribbean slope. In the Sarapiquí River Basin, eight hydropower plants were built between 1990 and 1999 and more projects are either under construction or proposed. The majority of these dams are small (<15 m tall) and operate as water diversion projects.
  • 2. While the potential environmental effects of individual projects are evaluated prior to dam construction, there is a need for consideration of the basin‐scale ecological consequences of hydropower development. This study was a first attempt to quantify the extent of river fragmentation by dams in the Sarapiquí River Basin.
  • 3. Using simple spatial analyses, the length of river upstream from dams and the length of de‐watered reaches downstream from dams was measured. Results indicated that there are currently 306.8 km of river (9.4% of the network) upstream from eight existing dams in the Sarapiquí River Basin and 30.6 km of rivers (0.9% of the network) with significantly reduced flow downstream from dams. Rivers upstream from dams primarily drain two life zones: Premontane Rain Forest (107.9 km) and Lower Montane Rain Forest (168.2 km).
  • 4. Simple spatial analyses can be used as a predictive or planning tool for considering the effects of future dams in a basin‐scale context. In the Sarapiquí River Basin, we recommend that future dam projects be constructed on already dammed rivers to minimize additional river fragmentation and to protect remaining riverine connectivity.
Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

13.
We investigated the summer ecology of juvenile steelhead trout Onchorhynchus mykiss and Chinook salmon O. tshawytscha in the context of habitat use and movement behaviour. The study area was a 14.8 km section of the Chehalis River, Washington, and is of particular interest due to recent proposals for both a flood retention dam and restoration actions in this watershed. Ten study reaches were paired in distance upstream and downstream from a central point where a passive integrated transponder antenna array was operated between late June and September 2014. Juvenile densities for each species were associated with reach‐scale habitat and temperature characteristics. Juvenile steelhead underwent upstream and downstream movements up to 7 km, although more fish from further away moved downstream than upstream. Juvenile steelhead repeated horizontal movements throughout the study period, but daily detections were not associated with temperature or flow. The majority (81%) of steelhead movements occurred between the hours of 04:00–07:00 and 18:00–21:00. Juvenile Chinook underwent a downstream migration that was nearly complete by the end of August. Most juvenile Chinook were detected just once and movements occurred on days with warmer stream temperature and higher flows. The majority of Chinook movements occurred at night. Although juvenile salmonids are often thought to have small home ranges during summer months, our results suggest that horizontal movements may be more prevalent than previously thought. Summer habitat should be defined by a network of suitable rearing reaches with connectivity available in both upstream and downstream directions.  相似文献   

14.
Movement and migration of fish are critical for sustaining riverine fish populations. Water resource development alters natural flow regimes and can disconnect habitats and interfere with hydrological cues for fish movement. Environmental flow releases can counter these impacts, but to be effective they must be based on quantitative flow–biota relationships. We used radio‐telemetry to investigate the association between flow and movement of Tandanus bostocki, a plotosid fish endemic to south‐western Australia. Movement was assessed for 15 adult fish at three temporal scales: weekly, daily and bihourly to reveal seasonal patterns in movement, movement around individual flow pulses, and to describe changes in home range respectively. We used a predictive modelling approach to assess the importance of discharge and other covariates on the directional distance travelled or linear home range size. Our seasonal and flow pulse study revealed that T. bostocki undertook larger downstream movements during higher flows and smaller upstream movements during lower flows. Daily movements tended to be downstream on the ascending limb of flow pulses and upstream on the descending limb. Flow‐dependent movements at weekly or daily time scales were relatively modest (typically hundreds of metres) and were moderated by time of year and gender; however, fish underwent a synchronised 1‐km movement upstream during the known reproductive period in October. The home range study revealed that T. bostocki had larger home ranges (night‐time foraging) when baseflow was elevated. These results can assist the design of customised environmental flows in the study river and other flow‐regulated rivers.  相似文献   

15.
Analysing how fish populations and their ecological communities respond to perturbations such as fishing and environmental variation is crucial to fisheries science. Researchers often predict fish population dynamics using species‐level life‐history parameters that are treated as fixed over time, while ignoring the impact of intraspecific variation on ecosystem dynamics. However, there is increasing recognition of the need to include processes operating at ecosystem levels (changes in drivers of productivity) while also accounting for variation over space, time and among individuals. To address similar challenges, community ecologists studying plants, insects and other taxa increasingly measure phenotypic characteristics of individual animals that affect fitness or ecological function (termed “functional traits”). Here, we review the history of trait‐based methods in fish and other taxa, and argue that fisheries science could see benefits by integrating trait‐based approaches within existing fisheries analyses. We argue that measuring and modelling functional traits can improve estimates of population and community dynamics, and rapidly detect responses to fishing and environmental drivers. We support this claim using three concrete examples: how trait‐based approaches could account for time‐varying parameters in population models; improve fisheries management and harvest control rules; and inform size‐based models of marine communities. We then present a step‐by‐step primer for how trait‐based methods could be adapted to complement existing models and analyses in fisheries science. Finally, we call for the creation and expansion of publicly available trait databases to facilitate adapting trait‐based methods in fisheries science, to complement existing public databases of life‐history parameters for marine organisms.  相似文献   

16.
River damming alters the physical–chemical variables of water and often causes compartmentalisation of aquatic habitats. Seasonality can add complexity to the longitudinal compartmentalisation. The spatial and temporal effects of these two phenomena on the structure of ichthyofauna from a tributary under the influence of damming were evaluated, based on the following hypotheses: (1) transition habitats have the greatest species richness; (2) community similarity decreases with increasing distance between sites; (3) conservation of free‐flowing areas upstream reservoir contributes to the maintenance of migratory species. To evaluate the effects of these two phenomena, twelve monthly fish samples (September/12 to August/13) were performed with gillnets in three sample areas distributed longitudinally in the tributary. Limnological variables were measured in the same sample areas to confirm compartmentalisation. We observed three distinct limnological compartments (lotic, transition and lentic), with increase differentiation during the rainy season. This compartmentalisation influenced fish fauna where localised communities exhibited different compositions among the three sampled habitats. During the rainy season, these differences become pronounced, with transition habitat showing greater species richness than the others. More pronounced differences in species composition and structure in extremes sampling sites were also observed. Migratory fish presented higher proportion of fish composition in lotic habitat. In conclusion, damming and seasonality acted concomitantly as modulators of fish fauna in a tributary influenced by damming. However, compartmentalisation of habitats was the primary driver of ichthyofauna community structure with the rainy season increasing differences in community composition.  相似文献   

17.
Pacific oyster is one of the leading species in world aquaculture, but heritability estimation applying mixed‐family approach has not been actively pursued. In this study, heritability for growth‐related traits in the Pacific oyster was first estimated by creating a single cohort of 45 families in a full‐factorial mating design consisting of nine sires and five dams. A total of 270 offspring were analysed and parentage assignment inferred by six microsatellite markers achieved 100% success. All parents contributed to the spawn and a total of 42 full‐sib families were represented. Using an animal model, heritability estimates at 12 months of age were 0.49 ± 0.25 for shell height, 0.36 ± 0.19 for shell length, 0.45 ± 0.23 for shell width and 0.35 ± 0.17 for wet weight. Genetic correlation between shell height and wet weight was quite high (0.79 ± 0.25), suggesting that direct selection of shell height, which is an easily measurable trait, also improves wet weight. The results obtained in this study indicate that growth‐related traits could be improved by exploiting additive genetic effects through selective breeding.  相似文献   

18.
The construction of fishways for upstream and downstream connectivity is the preferred mitigation measure for hydropower dams and other riverine barriers. Yet empirical evidence for effective design criteria for many species is missing. We therefore assembled a group of international fishway designers and combined their knowledge with available empirical data using a formal expert elicitation protocol and Bayesian networks. The expert elicitation method we use minimizes biases typically associated with such approaches. Demonstrating our application with a case‐study on the temperate Southern Hemisphere, we use the resulting probabilistic models to predict the following, given alternative design parameters: (i) the effectiveness of technical fishways for upstream movement of migratory fish; (ii) habitat quality in nature‐like bypasses for resident fish; and (iii) rates of mortality during downstream passage of all fish through turbines and spillways. The Fish Passage Network (Fish‐Net) predicts that fishways for native species could be near 0% or near 100% efficient depending on their design, suggesting great scope for adequate mitigation. Sensitivity analyses revealed the most important parameters as follows: (i) design of attraction and entrance features of technical fishways for upstream migration; (ii) habitat preferences of resident fish in nature‐like bypasses; and (iii) susceptibility of fish to barotrauma and blade strike during turbine passage. Numerical modelling predicted that mortality rates of small‐bodied fish (50–100 mm TL) due to blade strike may be higher for Kaplan than Francis turbines. Our findings can be used to support environmentally sustainable decisions in the planning, design and monitoring stages of hydropower development.  相似文献   

19.
Water resource development and non‐native species have been cited as primary drivers associated with the decline of native fishes in dryland rivers. To explore this topic, long‐term trends in the fish community composition of the Bill Williams River basin were studied over a 30‐year period (Arizona, USA). We sampled 31 sites throughout the basin that were included in fish surveys by Arizona Game and Fish in 1994–97 and the Bureau of Land Management in 1979–80. We found that non‐native species have proliferated throughout the entire basin, with greater densities in the lower elevations. Native species have persisted throughout most of the major river segments, but have experienced significant declines in frequency of occurrence and abundance in areas also containing high abundances of non‐native species. Next, we assessed the short‐term response of the fish assemblage to an experimental flood event from the system's only dam (i.e. Alamo Dam). In response to the flood, we observed a short‐term reduction in the abundance of non‐native species in sites close to the dam, but the fish assemblage returned to its preflood composition within 8 days of the event, with the exception of small‐bodied fish, which sustained lower postflood densities. Our findings demonstrate the importance of natural flow regime on the balance of native and non‐native species at the basin scale within dryland rivers and highlight minimal effects on non‐native fishes in response to short duration flood releases below dams.  相似文献   

20.
了解浮游生物对河流筑坝的响应,为高原河流的生态保护与可持续利用提供科学依据。基于野外调查、历史调研和室内实验,分别构建2007年（筑坝前）和2018年（筑坝后）火烧沟河流水生生态系统的Ecopath模型,通过对比分析筑坝前后的生态系统结构和功能及其系统特征,探讨筑坝对浮游生物的影响,并应用冗余分析（RDA）分析浮游生物与环境因子的相关性,识别出关键环境因子。结果表明,筑坝对浮游生物有显著影响,具体表现为：（１）浮游生物物种由2007年（筑坝前）的50种增加至2018年（筑坝后）的87种,密度和生物量均增加7.9倍,Shannon-Wiener多样性指数、Pielou均匀度指数均显著增加,但Margalef丰富度指数降低;（２）Ecopath模型结果显示,筑坝后生态系统趋向稳定,其周转率的上升、食物链的转变及混合营养效应的变化是浮游生物变化的重要原因;（３）冗余分析表明,筑坝后总磷（TP）、总氮（TN）、水温（WT）是影响浮游生物群落分布的主要环境因子。  相似文献   

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