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Strategic methodology to set priorities for sustainable hydropower development in a biodiversity hotspot
Abstract
Massive exploitation of freshwater systems for hydropower generation in developing countries is challenging sustainability due to cumulative environmental impacts in regions with high endemism. Habitat fragmentation is recognized as a major impact on river ecosystems. The nature and magnitude of connectivity loss depend on characteristics of the hydropower projects, and of the threatened fish communities. In areas where appropriate mitigation technology is lacking, there is a need to identify the fish species that are most at risk to better concentrate efforts. This paper aimed to set conservation priorities for sustainable hydropower development by analyzing native fish species and project characteristics. The Chilean ichthyogeographic province, an ecoregion with high endemism and massive hydropower projects development, has been considered as a case study. By using overlapping information on the characteristics of 1124 hydropower projects and distribution of native fish species, we identified three project categories of projects based on their need for mitigation. These were projects where mitigation was considered: a) not required (15%), b) required and feasible (35%), and c) required but challenging (50%). Projects where mitigation was not required were located at sites where native fish were absent and/or where water intakes allowed fish to pass. Interestingly, projects where mitigation was feasible were inhabited by a species assemblage that comprised the genus Trichomycterus, Diplomystes and Percilia, and the species Ch. pisciculus and B. maldonadoi. This finding emphasises the need to develop a multispecific fishway that can accommodate this group. Projects where mitigation would be difficult to achieve were located at sites with a variety of different assemblages, thus making a standard fish pass solution challenging and site-specific. This study advances understanding for the need to develop mitigation strategies and technologies in ecoregions of high endemism threatened by hydropower and to prioritize the construction of planned projects.
... www.nature.com/scientificreports/ they are very scarce for small species in South America 8 , and mainly for freshwater species in Chile to develop fishways 7 . This study evaluates the swimming capacity of three native small-bodied freshwater fish species from Chile (L T < 12 cm); Percilia irwini (Eigenmann, 1927), Cheirodon galusdae (Eigenmann, 1928), and Trichomycterus areolatus (Valenciennes 1840). ...
... irwini) 30 . These species inhabit basins with high anthropogenic pressure, and new knowledge is needed for the design of hydraulic criteria for fish passages 7 . In addition, most studies have been done on salmonids such as rainbow trout Oncorhynchus mykiss (Walbaum 1972), brown trout Salmo trutta (Linnaeus 1758), sockeye salmon O. nerka (Walbaum 1972) and coho salmon O. kisutchk (Walbaum 1972) 15,31,-33 , which are all introduced species in Chilean ecosystems 34 . ...
This study evaluated the effect of fish total length (LT) and three water temperatures (10, 15 and 20 °C) on the critical swimming speed (Ucrit) of the species Percilia irwini (2.9–6.3 cm LT), Cheirodon galusdae (3.4–5.5 cm LT), and Trichomycterus areolatus (4.0–6.3 cm LT). An Ucrit estimation model was constructed for each species as a function of temperature and size. The results showed mean Ucrit for P. irwini of 44.56, 53.83 and 63.2 cm s⁻¹ at 10, 15 and 20 °C, respectively: 55.34, 61.74 and 70.05 cm s⁻¹ for C. galusdae and 56.18, 63.01 and 71.09 cm s⁻¹ for T. areolatus. Critical velocity depended on the interaction between species, body length and water. The swimming performance increased significantly with rising temperature in all three species. The velocity also increased with greater fish total length. After controlling for fish total length, velocity also increased with higher temperature in the three species. This research is relevant to small fish species that require conservation measures.
... For instance, Adapting hydropower to hydrological dynamics will benefit ecosystems and biodiversity. (Fantin-Cruz et al. 2015;Kuriqi et al. 2019;Kuriqi et al. 2020;Laborde et al. 2020;Rosero-López et al. 2019) 2 Re-assessing national hydropower potential based on dynamic environmental flows and climate change scenarios. ...
... Improvement on management of river basins. (Couto and Olden 2018;Fantin-Cruz et al. 2015;Flecker et al. 2022;Gasparatos, Ahmed, and Voigt 2021;Habersack et al. 2016;Laborde et al. 2020;Vasconcelos et al. 2021) 6 Combining new hydropower turbines and aquatic biodiversity-friendly technologies with nature-based solutions. ...
... The rivers within the studied basins flow predominantly from East to West and are characterised by a total length between 200 and 400 km, Strahler's orders up to eight, and annual mean discharges at the mouth between 100 and 1000 m 3 /s ( Table 1). All the studied rivers flow from the Andes through the Central Valley to the Pacific Ocean and are characterised by river longitudinal slopes in the Andes between 5 and 10% [33,34]. Most of the studied river networks are free-flowing, with the exception of the Rapel, Maule and Biobío rivers that accommodate large reservoirs for hydropower production and irrigation. ...
... Consistently, these are the most fragmented river networks [35] ( plants with a total potential of 0.65 GW are under environmental evaluation or construction in the study area [36]. characterised by river longitudinal slopes in the Andes between 5 and 10% [33,34]. Most of the studied river networks are free-flowing, with the exception of the Rapel, Maule and Biobío rivers that accommodate large reservoirs for hydropower production and irrigation. ...
Exact knowledge of the physical structures of different river sections that govern their ecological structure and function is essential for the efficient conservation and management of riverine ecosystems. Eleven Andean river basins (Maipo, Rapel, Mataquito, Maule, Itata, Biobío, Toltén, Valdivia, Bueno and Puelo) comprise large scale latitudinal and altitudinal gradients and accommodate 71% of the Chilean population that strongly depend on their ecosystem services. Here, based on 16 hydrogeomorphic variables (on basin, valley and channel scales), we assessed the riverine landscapes (Functional Process Zones; FPZs) of these river basins using a top-down multivariate statistical approach. Two steep valley and downstream slope FPZs, three sinuous FPZs and two braided FPZs emerged in 8906 river sections. The proportion of the occurrence of FPZs was characterised by a clear latitudinal pattern which is strongly related to the proportions of each river basin within the large morphostructural units of Chile. As such, the proportion of each river basin within the Andes Cordillera, Central Valley and Coastal Cordillera is a strong driver of the fluvial geomorphology and, thus, of the FPZs’ arrangement in each river network. FPZ classification captured geomorphic diversity that coincided with the latitudinal and altitudinal gradients of Chilean Andean river basins strongly related to the hydrological characteristics of the assessed river basins and large scale spatial distribution of fish fauna endemism. As such, the identified large geomorphic units (FPZs) that are strongly tied up with hydrology and ecology hierarchies of riverine landscape provide robust operational tools that can be instrumental for river ecosystem monitoring and management at a basin scale.
... facilitating the movement of potamodromous species to maintain gene flow). CBCs could also be a valuable mitigation tool when passage of multiple small-bodied fish that have often been ignored during fish passage development is required, such as those found in parts of the Southern Hemisphere (Wilkes et al., 2017), including Chile (Laborde et al., 2020) and New Zealand (Franklin and Gee, 2019). In this scenario, design optimisation might involve reducing the space between bristle clusters (the opposite of what was tested in this study) to selectively facilitate passage for native small-bodied species while limiting the dispersal of larger-bodied non-native ones. ...
... Some publications reported the distribution this species from Lanalhue Lake to Calle-Calle River (Campos 1982, Dyer 2000. Nevertheless, recent studies reported a narrower distribution area of 38.1 km long in the city of Valdivia and Calle-Calle River (Soto et al. 2018, Laborde et al. 2020. However, records of this species are scarce and only a few specimens have been captured (Soto et al. 2018). ...
... No species-specific monitoring programs have been performed. Nonetheless, various publications report that this species has maintained its distribution, occupying an area of 514 km in length between Toltén River and Chiloé Island (Laborde et al. 2020). ...
... Such planning should be based on proven solutions within hierarchical mitigation strategy: avoidance, minimization, restoration, and biodiversity offsets [5]. While some recent studies suggest planning strategies that may minimize some of the effects posed by barriers in Chilean Andean river basins [27,57], we postulate that the avoidance strategy should urgently be considered. This is valid especially in expected near future climate change scenarios, where up to 40% declines in river discharges in central Chile are expected [58], and as such, alternative energy sources should be evaluated. ...
Longitudinal connectivity is the main attribute of river ecosystems and is essential for the maintenance of aquatic biota. When longitudinal connectivity decreases in a river network, abundance of some fish species decreases, and local extinctions may occur. Such abundance decreases and extinctions affect local assemblage structure (alpha diversity) and result in a high degree of dissimilarity among local assemblages (higher beta diversity). Specific ecological mechanisms that are behind these biodiversity changes induced by connectivity loss remain poorly understood. Here, we assessed the effects of fragmentation at the local and basin level, as well as local environmental variables on local fish diversity patterns in eight Andean river basins in central Chile (32–39° S). The results indicated that fish assemblages inhabiting pool habitats in highly fragmented basins were characterized by significantly lower species richness and alpha diversity mainly driven by absence of fish species with high dispersion capacities. Our results highlight the importance of the effects of barrier cascades upstream as drivers of local native fish diversity. Sustainable hydropower development necessitates system scale planning of the placement of future barriers and should consider both local and basin scale biodiversity indicators.
... These HPs have large reservoirs, leading to relatively large CF and low sustainability compared with the HPs with small reservoirs, which is attributed to their direct GR and indirect GHG emissions from the extra construction. Evidence from previous studies shows that the combined operation modes with only one large reservoir in the first cascade can be more sustainable than the separate operation modes owing to the ability to dispatch water resources among cascade HPs in the lower reaches (Bozorg Haddad et al., 2008;Feng et al., 2018;Laborde et al., 2020;Ren and Feng, 2021;Tariku et al., 2021). In this study, for example, the Shiziping Plant had the largest reservoir with annual regulating ability among the studied HPs. ...
Hydropower is a source of climate-friendly energy; however, its ecological impacts have been criticized. Few studies have considered the greenhouse gas (GHG) emissions resulting from ecosystem restoration. This study proposes a techno-ecological synergy framework based on life cycle assessment (LCA) to evaluate 34 hydropower plants (HPs) in the upper reaches of the Yangtze River from GHG supply and demand side perspectives. Our results show that the demand unit carbon footprint of the 34 HPs ranged from 5.43 to 49.36 g CO2-eq/kWh, while the imputed GHG emissions from ecosystem restoration occupied 1.22 % to 30.35 %. The unit carbon footprint of large HPs were larger than those of small HPs, and both were positively correlated with the installed capacity of the HPs. All the HPs were unsustainable at the local scale and relied on regional ecosystem supplies. The Sobol' sensitivity analysis and Monte Carlo simulations demonstrated the reliability of our results. Finally, our results were used to consider the related policy implications.
... Applying an exploratory scenario storyline approach, narratives associated with the driving forces and critical uncertainties of hydropower development in the LMB were identified and evaluated ( Fig. 2.5 and Appendix D of SI). These drivers and uncertainties were identified based on prior studies where both negative and positive impacts of hydropower development of different types and sizes have well been explored and discussed (Fan et al., 2015;Zhang et al., 2016;Intralawan et al., 2018;Williams, 2019;Laborde et al., 2020;Trung et al., 2020;Atkinson, 2021), with many concluded that developing hydropower on the river mainstream could lead to severe and irreversible environmental and social impacts (Le et al., 2020;Trung et al., 2020;Yoshida et al., 2020). Drivers allow the establishment of various assumptions used for deriving distinct future alternative narratives that can be implemented to help the LMB Countries achieving their goals of ensuring access to affordable and clean energy, while pursuing ecologically sustainable development. ...
Transboundary river basins across developing countries, such as the Lower Mekong River Basin (LMB), are challenging to manage given frequent divergences on development and conservation priorities. Driven by needs to sustain economic performance and reduce poverty, the LMB countries are embarking on significant land use changes in the form of more hydropower dams, to satisfy growing energy demands. This pathway could lead to irreversible changes to the ecosystem of the Mekong River, if not properly managed. Given the uncertain environmental externalities and trade-offs associated with further hydropower development and operation in the LMB, this research develops four plausible scenarios of future hydropower operation, and assesses their likely impact on streamflow and instream total suspended solids and nitrate loads of the Mekong River. The findings suggest that further hydropower operations on either tributary or mainstream could result in annual and wet season flow reduction between 11 and 25% while increase dry season flows by 1 to 15%, when compared to a business-as-usual scenario. Conversely, hydropower operation on both tributary and mainstream could result in dry season flow reduction between 10 and 15%. Both instream TSS and nitrate loads are forecasted to reduce under all three scenarios by as much as 78 and 20%, respectively, compared to the business-as-usual one. These effects are predicted to magnify under extreme climate conditions with dry season flow, TSS, and nitrate levels reduced by as much as 44, 81 and 35%, respectively, during a projected extreme dry climate condition, but less severe under improved operational alternatives. With further hydropower development in the LMB being highly unavoidable, these findings can inform effective transboundary management pathways for balancing electricity generation and protection of riverine ecology, water and food security, and people livelihoods.
... The literature indeed shows conclusions of various hydropower case studies that oppose and questions each other. For instance, Laborde et al. (2020) contradict Gaete-Morales et al. (2018) by pointing out that plans to exploit substantial hydropower potential in Chile directly oppose the requirement to protect unique native freshwater fish fauna. Furthermore, Chile is a water-stressed country (Mekonnen and Hoekstra, 2016), which could be conflicting with water resources and biodiversity. ...
Along with other low-carbon combustion-free energy sources, hydropower is considered a valuable tool for mitigating the current climate and ecological crisis and achieve environmental sustainability. However, it is still unclear to what extent hydropower is or not environmentally sustainable. The literature reveals i) that no truly holistic assessments have been carried out and ii) that there are contradictory results and conclusions. The present study addresses this gap by conducting a holistic assessment, using eight biophysical indicators of different approaches, and taking two different hydropower plant schemes as study cases. The results of the assessment show that the run-of-river hydropower plant study case is by far more environmentally sustainable than the dam hydropower plant scheme. As hydropower schemes and sizes vary, it is highlighted the importance of including as many indicators as possible to ensure broader and complete assessments and the avoidance of bias in the conclusions and ease comparison with other low-carbon combustion-free energy sources and their technologies. Moreover, the present study addresses how and within which parameters the environmental sustainability of hydropower is usually determined. The complementary set of indicators provided here, which have different scope and complexity, could be adopted for improving future decision-making in energy policies and specifically for hydropower.
... Globally, proactive planning of future barriers is urgently needed to ensure the conservation of rivers with their biodiversity and ecosystem services they provide (Hermoso et al., 2018;Linke et al., 2019). As such, projects that facilitate possibility of mitigation and allow fish movement to minimise effects on fish diversity should be considered and, therefore, development of mitigation technology that considers bounded requirements is urgent (Laborde et al., 2020). Such technology apart from frequency of upstream movements should concentrate on the technologies efficacy to sustain fish populations in fragmented systems and also evaluate probabilities of downstream movements of larvae and adults through the reservoir and past the barrier (Pelicice et al., 2015;Pompeu et al., 2012). ...
Connectivity plays a crucial role in maintaining the structural and functional attributes of river networks. Therefore, the loss of connectivity (fragmentation) alters the functioning and diversity patterns of the biota at local and regional scales. The global hydropower boom is one of the main drivers of river network fragmentation, with significant effects on the diversity of riverine biota. Analyses of beta diversity of fish assemblages in rivers with different degrees of fragmentation can give new insights into mechanisms that contribute to the responses of these assemblages to fragmentation.
Here, fish beta diversity within six river networks of central Chile with different levels of fragmentation was studied to assess the responses of fish assemblages to fragmentation. A hypothesis of a significant effect of fragmentation on the beta diversity of native and non-native fish in riffles and pools was tested. This effect is expected to be modulated by both changes in environmental heterogeneity and direct obstruction of natural dispersal routes.
Beta diversity based on variation of assemblage structure and environmental heterogeneity showed significant differences among river networks. Fish beta diversity showed a clear response to fragmentation in recently fragmented rivers. Specifically, the beta diversity of native fishes in pools and non-native fishes in riffles decreased with increase of the ratio between the longest non-fragmented sections of the river network to the total length of the network. These effects of fragmentation on fish assemblages were modulated by the biological features of each species, and open-water species were most severely affected.
These results have significant implications for planning of the placement of new barriers in river networks subjected to hydropower boom. Planning of the placement of new barriers should consider the maintenance of long, connected sections within river networks in order to minimise the effects of fragmentation on fish biodiversity.
... However, knowledge on the hydraulic preferences and swimming abilities of specific target species and life stages may enable the construction of fish passes with improved effectiveness, even for little-known benthic species . Laborde et al. (2020) pronounced the importance of further research on the characteristics of relevant species to enhance the development of sustainable hydropower. ...
Modern ethohydraulics is the study of the behavioral responses of swimming fish to flow fields. However, the exact drag forces experienced by fish remain poorly studied; this information is required to obtain a better understanding of the behavioral responses of fish and their current resistance strategies. We measured near-ground frontal drag forces on preserved individuals of three benthic fish species, round goby (Neogobius melanstomus), gudgeon (Gobio gobio) and bullhead (Cottus gobio), in a flow channel. The forces were compared to acoustic Doppler velocity (ADV) measurements and fish tracking data based on video observations of live fish in the flow channel. Overall, we observed drag coefficients (CD) of ∼10⁻³ at Reynolds numbers ∼10⁵. The frontal drag forces acting on preserved fish with non-spread fins ranged from -1.96 mN*g⁻¹ (force per fish wet weight, velocity 0.55 m*s⁻¹) to 11.01 mN*g⁻¹ (velocity 0.85 m*s⁻¹). Spreading the fins strongly increased the drag forces for bullhead and round goby. In contrast, the drag forces were similar for gudgeon with spread fins and all fish with non-spread fins. Video tracking revealed no clear relationship between the position of the fish in the flow field and the forces experienced by the preserved fish at these positions. Collectively, these results suggest that i) the differences in frontal drag forces between species are small in homogenous flow, ii) individuals chose their position in the flow field based on factors other than the drag forces experienced, and iii) whether fins are spread or non-spread is an essential quality that modulates species-specific differences. The methodology and results of this study will enable integration of flow measurements, fish behavior and force measurements and inform ethohydraulics research. More advanced force measurements will lead to a detailed understanding of the current resistance strategies of benthic fish and improve the design of fish passes.
River classification is a necessary starting point for understanding river ecosystems and developing management guidelines. Using GIS to analyse an Andean river basin, we compare the application of two geomorphic classification methods at the segment scale: The Geomorphic Units Survey Classification System (GUS) and the Functional Process Zones (FPZ). Segment definition follows a manual procedure in GUS and a semi‐automated procedure in FPZ. Our objective was to assess the relationship between geomorphology and fish assemblages' structure. Fish sampling was carried out in collaboration with participants from local indigenous Mapuche‐Pewenche communities. Non‐parametric multivariate statistical analyses were conducted in order to quantify and describe geomorphic patterns and whether fish assemblages responded consistently with river classifications. Both classifications give insight into the physical characteristics of rivers, such as slope and floodplain width, that make habitat available for different fish assemblages. The two methods provide results that consistently coincide in their identification of geographic distribution and main geomorphic variables of different river types (geomorphic types) throughout the river network. The variation of different river geomorphologies was associated with variation in fish assemblage structure. Geomorphic variables that best characterize the distribution pattern of fish assemblages were elevation, confinement and valley floor width. Confined rivers accommodated highly similar fish assemblages dominated by invasive trout (Salmo trutta and Oncorhynchus mykiss). Unconfined rivers located at higher elevations had greater temporal variability and were mainly composed of trout and native catfish Trichomycterus areolatus. Semiconfined rivers presented the highest geomorphic variability and were associated with high spatial and temporal variability of fish assemblages characterized by both native and non‐native species. The association between fish assemblages and fluvial geomorphology could help in prioritizing rivers for exotic fish species control. These findings should aid in restoring highly intervened Andean rivers and improving management techniques in basins with a variety of human activities.
Determining the priorities for sustainable development involves critical problems identifying, the conditions creating necessary for successfully solving such problems, and identifying a set of methods and tools to ensure that these conditions are met. The existing quantitative approaches to the priorities definition do not consider the problems of resource provision of scientific priorities. The developed expert system makes it possible to use effectively multilevel information-logical structures for the systematic analysis of scientific priorities according to many criteria. It allows ensuring the transition from research goals to methods of achieving these goals, the choice of specific means and the development of the necessary research methodology.
Further reservoir-based hydropower development can contribute to the United Nations’ sustainable development goals (SDGs) on affordable and clean energy, and climate action. However, hydropower reservoir operation can lead to biodiversity impacts, thus interfering with the SDGs on clean water and life on land. We combine a high-resolution, location-specific, technical assessment with newly developed life cycle impact assessment models, to assess potential biodiversity impacts of possible future hydropower reservoirs, resulting from land occupation, water consumption and methane emissions. We show that careful selection of hydropower reservoirs has a large potential to limit biodiversity impacts, as for example, 0.3% of the global hydropower potential accounts for 25% of the terrestrial biodiversity impact. Local variations, e.g. species richness, are the dominant explanatory factors of the variance in the quantified biodiversity impact and not the mere amount of water consumed, or land occupied per kWh. The biodiversity impacts are mainly caused by land occupation and water consumption, with methane emissions being much less important. Further, we indicate a trade-off risk between terrestrial and aquatic biodiversity impacts, as due to the weak correlation between terrestrial and aquatic impacts, reservoirs with small aquatic biodiversity impacts tend to have larger terrestrial impacts and vice versa.
An understanding of how genetic variability is distributed in space is fundamental for the conservation and maintenance of diversity in spatially fragmented and vulnerable populations. While fragmentation can occur from natural barriers it can also be exacerbated by anthropogenic activities such as hydroelectric power plant development. Whatever the source, fragmentation can have significant ecological effects, including disruptions of migratory processes and gene flow among populations. In Chile, the Biobío river basin exhibits a high degree of habitat fragmentation due to the numerous hydroelectric power plants in operation, the number of which is expected to increase following new renewable energy use strategies. Here, we assessed the effects of different kinds of barriers on the genetic structure of the endemic freshwater fish Percilia irwini, knowledge that is critically needed to inform conservation strategies in light of current and anticipated further fragmentation initiatives in the system. We identified 8 genetic units throughout the entire Biobío system with high effective sizes. A reduced effective size estimate was however observed in a single population located between two impassable barriers. Both natural waterfalls and human made dams were important drivers of population differentiation in this system, however, dams affect genetic diversity differentially depending on their mode of operation. Evidence of population extirpation was found in two river stretches limited by upstream and downstream dams. Significant gene flow in both directions was found among populations not separated by natural or anthropogenic barriers. Our results suggest a significant vulnerability of P. irwini populations to future dam development and demonstrate the importance of studying basin‐wide data sets with genetic metrics to understand the strength and direction of anthropogenic impacts on fish populations.
To achieve sustainable development of hydroelectric resources, it is necessary to understand their availability, variability, and the expected impacts of climate change. Current research has mainly focused on estimating hydropower potential or determining the optimal locations for hydropower projects without considering the variability and historical trends of the resources. Herein, the hydropower potential variability from reconstructed streamflow series estimated with a non-parametric gap-filling method and geographic information systems (GIS) techniques are analyzed. The relationships between hydropower and large-scale climate variability, expressed by sea surface temperature, are explored. Finally, we project hydropower potential through 2050 using 15 global circulation models with representative concentration pathway (RCP) 4.5. We used four watersheds in central Chile as a case study. The results show significant interannual and inter-basin hydropower potential variability, with decreasing trends over time modulated by alternating positive and negative decadal trends; these modulations exhibit greater intensities than the general trends and are attributable to climatic oscillations such as El Niño. Future scenarios indicate high hydropower availability and a possible over-investment in hydroelectric plants in two of the four studied watersheds. Results show the need to improve the current policies that promote hydropower development including hydropower resource variability in order to achieve optimal, sustainable hydropower development worldwide.
Background:
Fragmentation (establishment of barriers e.g., hydropower dams, reservoirs for irrigation) is considered one of the greatest threats to conservation of river systems worldwide. In this paper we determine the fragmentation status of central Chilean river networks using two indices, namely Fragmentation Index (FI) and Longest Fragment (LF). These are based on the number of barriers and their placement as well as river length available for fish movement. FI and LF were applied to eight Andean river basins of central Chile in order to assess their natural, current (2018) and future (2050) fragmentation at the doorstep of a hydropower boom. Subsequently, we exemplify the use of these indices to evaluate different placement scenarios of new hydropower dams in order to maximize hydropower use and at the same time minimize impact on fish communities.
Results:
In the natural scenario 4 barriers (waterfalls) were present. To these 4 barriers, 80 new ones of anthropogenic origin were added in the current (2018) scenario, whereas 377 new barriers are expected in near future (2050). Therefore, compared to the ‘natural’ scenario, in 2050 we expect 115-fold increase in fragmentation in analysed river systems, which is clearly reflected by the increase of the FI values in time. At the same time, the LF diminished by 12% on average in the future scenario. The fastest increase of fragmentation will occur in small and medium rivers that correspond to 1st, 2nd and 3rd Strahler orders. Finally, case study on configuration of potential hydropower plants in the Biobio basin showed that hydropower output would be maximized and negative effects on fish communities minimised if new hydropower plants would be located in tributaries of the upper basin.
Conclusions:
Fragmentation of Chilean Andean river systems is expected to severely increase in near future, affecting their connectivity and ecological function as well as resilience to other anthropogenic stressors. Indices proposed here allowed quantification of this fragmentation and evaluation of different planning scenarios. Our results suggest that in order to minimise their environmental impact, new barriers should be placed in tributaries in the upper basin and river reaches above existing barriers.
Developing and testing new fishway designs is important to improve these facilities. Discharge-efficient passage systems are required in Mediterranean regions and other areas with dry climates. The present study compares the passage performance of the Iberian barbel, Luciobarbus bocagei (Steindachner, 1864), a potamodromous cyprinid, negotiating two different types of vertical slot fishways (VSF): a standard VSF and a multi-slot VSF (MSF). Results show that differences exist between configurations in the number of fish movements through the first slot. The I. barbel performed a significantly higher number of movements in the MSF. However, no differences were found in the entrance time and entry efficiency. The performance was similar between configurations in terms of successes, suggesting that both fishways could be used to restore longitudinal connectivity. Nevertheless, the MSF is a more discharge-efficient configuration, since it requires 31% less water to operate for the same water depth in the pools. Consequently, the velocity and turbulence have lower magnitudes which generally favour the negotiation by smaller individuals. Since it is a more discharge-efficient and cost-efficient configuration, future studies should focus on the passage performance of smaller species to determine if MSF is a useful solution for the whole fish community.
More than a hundred hydropower dams have already been built in the Amazon basin and numerous proposals for further dam constructions are under consideration. The accumulated negative environmental effects of existing dams and proposed dams, if constructed, will trigger massive hydrophysical and biotic disturbances that will affect the Amazon basin’s floodplains, estuary and sediment plume. We introduce a Dam Environmental Vulnerability Index to quantify the current and potential impacts of dams in the basin. The scale of foreseeable environmental degradation indicates the need for collective action among nations and states to avoid cumulative, far-reaching impacts. We suggest institutional innovations to assess and avoid the likely impoverishment of Amazon rivers.
Following study of the external morphology and its unmatched variability throughout ontogeny and a re-examination of selected morphological characters based on many specimens of diplomystids from Central and South Chile, we revised and emended previous specific diagnoses and consider Diplomystes chilensis , D. nahuelbutaensis , D. camposensis , and Olivaichthys viedmensis (Baker River) to be valid species. Another group, previously identified as Diplomystes sp., D . spec., D . aff. chilensis , and D . cf. chilensis inhabiting rivers between Rapel and Itata Basins is given a new specific name ( Diplomystes incognitus ) and is diagnosed. An identification key to the Chilean species, including the new species, is presented. All specific diagnoses are based on external morphological characters, such as aspects of the skin, neuromast lines, and main lateral line, and position of the anus and urogenital pore, as well as certain osteological characters to facilitate the identification of these species that previously was based on many internal characters. Diplomystids below 150 mm standard length (SL) share a similar external morphology and body proportions that make identification difficult; however, specimens over 150 mm SL can be diagnosed by the position of the urogenital pore and anus, and a combination of external and internal morphological characters. According to current knowledge, diplomystid species have an allopatric distribution with each species apparently endemic to particular basins in continental Chile and one species ( O. viedmensis ) known only from one river in the Chilean Patagonia, but distributed extensively in southern Argentina.
A rocky ramp fishway is one of the Nature like fishway, comprises a long sloping channel and boulders on a slope (Katopodis et al., 2001). The turbulence and backwater around the boulders creates refuges of decreased local flow where fish can rest. However, recent studies have shown that turbulent flow may influence fish migration (Smith et al., 2006). This paper is focused on boulder arrangement and height of boulder on rocky ramp fishway. The swimming performance of char (Salvelinus richardson) and freshwater sculpin (Cottus pollux) around boulders on experimental channel were observed using ultra-high-speed cameras, and the appropriate arrangement of boulders for each species was considered. In total, 27 hydraulic conditions were assessed considering variable distributions, shapes, heights of the boulders as well as variable flow depths by observing swimming behavior for each condition. Laboratory measurement shows that sculpin, which are bottom fish, require a density, and several linear arrangements of boulders to allow migration. As increasing the vertical low-velocity area, which is created behind high boulders does not always result in a good outcome for sculpin. However, this solution is not suitable for char; therefore, a diverse arrangement of boulders is required on individual rocky ramp fishways to allow the movement and migration of multiple species. We propose to add cloister in the fishway for free migration of weak swimmer.
Fish passage research for Southern Hemisphere species lags significantly behind that for Northern Hemisphere species. This is despite there being a relatively high prevalence of diadromous species relying on free access between marine and freshwater environments to complete their life cycles. With an emphasis on New Zealand experiences, this paper discusses some of the challenges associated with transferring knowledge and methods from the Northern Hemisphere, and highlights the need for novel approaches for progressing fish passage research in the Southern Hemisphere. One of the most significant challenges is that many Southern Hemisphere fish species undertake their main upstream migrations as small bodied juveniles that range in size from 15-60 mm. This precludes the use of most state-of-the-art biotelemetry methods (e.g. PIT and acoustic tagging) for studying behavior, because tags are too large. It also means there is a need for greater focus on the impact of small instream structures, e.g. culverts, on connectivity. A further constraint is that the fundamental ecology and basic swimming capabilities of many Southern Hemisphere fish species are poorly understood, limiting the ability to establish whether existing solutions are transferable. The unique behavior of some Southern Hemisphere species (e.g. the ability to climb wet surfaces) opens up new avenues of fish passage research and a need for innovative approaches to finding solutions. To maximize these opportunities there is a need to embrace inter-disciplinary approaches and improve knowledge sharing.
In an effort to ensure energy independence and exploit mineral resources, the
governments of Amazonian countries are embarking on a major dam building drive on the
basin’s rivers, with 191 dams finished and a further 246 planned or under construction. This
rush to harvest the basin’s vast renewable energy capacity has come without proper consideration
of the likely negative environmental externalities on the world’s most speciose
freshwater and terrestrial biotas. Here we highlight the economic drivers for hydropower
development and review the literature to summarise the impacts of dam building on Amazonian
biodiversity.We identify both direct and indirect impacts through the anticipated loss,
fragmentation and degradation of riparian habitats. We then propose a series of measures to
assess, curb and mitigate the impacts of destructive dams on Amazonian biodiversity.
Basin-scale planning is needed to minimize impacts in mega-diverse rivers
Diplomystidae is well known as the oldest catfish family in the order Siluriformes. In Chile three of the six described species are present (genus Dyplomystes), distributed allopatrically in rivers from the Rapel Basin to the Valdivia Basin (34°S - 40°S), and some isolated populations of unidentified diplomystids in the Baker Basin (47°S). In this study we analyze the stomach content of individuals of Diplomystes from all hydrological drainages in which populations are currently present in Chile, including the Baker River. A total of 175 individuals were analyzed from which 90.3% were juveniles. Results show that, regardless of the provenance of individuals analyzed, larvae of the insect family Chironomidae were the most consumed item. The only exception occurred in the Toltén Basin, whose population consumed mostly larvae of the insect family Simulidae. No marked differences were found between the diet of juveniles and adults, except for the presence of crustaceans of the genus Aegla in adults. These results confirm a carnivore and generalist diet for the genus Diplomystes, with no changes along the latitudinal gradient in Chile.
The Chilean native freshwater ichthyofauna is composed of 11 families, 17 genera and about 44 species, including two lampreys. The Chilean biogeographic province has 81% of the species endemic, 40% of which are classified as endangered. The most abundant groups are the siluriforms (11 species), osmeriforms (9 species) and atheriniforms (7 species). Other groups represented in Chile are the cyclostomous Petromyzontiformes (2 species), and the teleostean characiforms (4 species), cyprinodontiforms (6 species), perciforms (4 species) and mugiliforms (1). The South Central area of the Chilean Province has the highest species richness, whereas the northern and southern areas are poorer in species numbers. Due to its origin, percentage of endemism and primitive characters, the ichthyological fauna of Chile has a high biogeographic and conservation value, however, there are important knowledge gaps in the systematics, distribution and biology of these freshwater fishes.
Human population growth, economic development, climate change, and the need to close the electricity access gap have stimulated the search for new sources of renewable energy. In response to this need, major new initiatives in hydropower development are now under way. At least 3,700 major dams, each with a capacity of more than 1 MW, are either planned or under construction, primarily in countries with emerging economies. These dams are predicted to increase the present global hydroelectricity capacity by 73 % to about 1,700 GW. Even such a dramatic expansion in hydropower capacity will be insufficient to compensate for the increasing electricity demand. Furthermore, it will only partially close the electricity gap, may not substantially reduce greenhouse gas emission (carbon dioxide and methane), and may not erase interdependencies and social conflicts. At the same time, it is certain to reduce the number of our planet’s remaining free-flowing large rivers by about 21 %. Clearly, there is an urgent need to evaluate and to mitigate the social, economic, and ecological ramifications of the current boom in global dam construction.
Most artificial fish passes have been developed in Northern temperate rivers and are designed to serve large, migratory sport fish species (mostly salmonids). Experience in construction and maintenance of fish passes show that salmon-criteria are not adequate for flat-land rivers and non-sport fishes. Consequently, over the last decade, design criteria have changed to take requirements of target species into account. Extrapolation of these concepts to rivers in the Southern Hemisphere with different hydrological conditions and fish community composition is not straight forward. This review focuses on requirements for an adequate hydraulic design of passes for non-sport fish species bodied (
Globally, diadromous species are at risk from fragmentation by damming of rivers, and a host of other anthropogenic factors. On the United States Atlantic Coast, where diadromous fish populations have undergone dramatic declines, restoration programs based on fishway construction and hatcheries have sustained remnant populations, but large-scale restoration has not been achieved. We examine anadromous fish restoration programs on three large Atlantic Coast rivers, the Susquehanna, Connecticut, and Merrimack with multiple mainstem hydropower dams, most with relatively low generating capacity. Mean passage efficiencies through fishways on these rivers from the first dam to the spawning grounds for American shad are less than 3%. The result is that only small fractions of targeted fish species are able to complete migrations. It may be time to admit failure of fish passage and hatchery-based restoration programs and acknowledge that significant diadromous species restoration is not possible without dam removals. The approach being employed on the Penobscot River, where dams are being removed or provided the opportunity to increase power generation within a plan to provide increased access to habitat, offers a good model for restoration. Dammed Atlantic Coastal rivers offer a cautionary tale for developing nations intent on hydropower development, suggesting that lasting ecosystem-wide impacts cannot be compensated for through fish passage and hatchery technology.
Riverine macrosystems are described here as watershed-scale networks of connected and interacting riverine and upland habitat patches. Such systems are driven by variable responses of nutrients and organisms to a suite of global and regional factors (eg climate, human social systems) interacting with finer-scale variations in geology, topography, and human modifications. We hypothesize that spatial heterogeneity, connectivity, and asynchrony among these patches regulate ecological dynamics of whole networks, altering system sensitivity, resistance, and resilience. Long-distance connections between patches may be particularly important in riverine macrosystems, shaping fundamental system properties. Furthermore, the type, extent, intensity, and spatial configuration of human activities (eg land-use change, dam construction) influence watershed-wide ecological properties through effects on habitat heterogeneity and connectivity at multiple scales. Thus, riverine macrosystems are coupled social–ecological systems with feedbacks that influence system responses to environmental change and the sustainable delivery of ecosystem services.
Diplomystidae is well known as the oldest catfish family in the order Siluriformes. In Chile three of the six described species are present (genus Dyplomystes), distributed allopatrically in rivers from the Rapel Basin to the Valdivia Basin (34°S -40°S), and some isolated populations of unidentified diplomystids in the Baker Basin (47°S). In this study we analyze the stomach content of individuals of Diplomystes from all hydrological drainages in which populations are currently present in Chile, including the Baker River. A total of 175 individuals were analyzed from which 90.3% were juveniles. Results show that, regardless of the provenance of individuals analyzed, larvae of the insect family Chironomidae were the most consumed item. The only exception occurred in the Toltén Basin, whose population consumed mostly larvae of the insect family Simulidae. No marked differences were found between the diet of juveniles and adults, except for the presence of crustaceans of the genus Aegla in adults. These results confirm a carnivore and generalist diet for the genus Diplomystes, with no changes along the latitudinal gradient in Chile.
The genus Trichomycterus includes nearly 120 species that generally inhabits at the neotropical river headwaters. In Chile this genus has a wide distribution: T. chungaraensis, T. laucaensis and T. rivulatus live at the altiplano, while T. areolatus distributes from the III to the X chilean regions with the wider extension living in simpatry with T. chiltoni in Biobio basin. The habitat diversities colonized by this genus would have driven morphological changes that were analyzed by geometric morphology.Seven type I and II landmarks were fixed, and a superposition was done by GPA (General Procruster Analysis). To describe relations between species RWA (Relative warps Analysis) was used, in which the first two RW explain 67, 22% and a UPGMA was performed. A strong relationship between T. chungaraensis, T. laucaensis and T. rivulatus was found; being different from T. areolatus and T. chiltoni which were similar. These form relationship would be associated with geographic species distributions that correspond to Titicaca and Chilean provinces respectively
T rophic ecology and reproductive aspects of T richomycterus areolatus (Pisces, Trichomycteridae) in irrigation canal environments. Twelve of the sixteen species of fishes present in the Itata river basin enter the irrigation canals at least once a year, constituting a habitat that is frequently utilized by the native fish assemblages. However, only Trichomycterus areolatus, a native siluriform, is found in great number throughout the entire year, being the dominant species of such artificial environments. Among the factors that could explain the relative success of T. areolatus are its benthonic habits, adaptation to rithral habitat, an offer of trophic resources that is in line with its feeding habits, and a lower abundance of predators in the canals. In this study, the trophic ecology of this species in 174 individuals inhabiting the Itata river (Octava Región, Chile) and 231 from irrigation canals that arise from this river are analyzed and compared. In addition, the length-weight relationship and seasonal frequencies of reproductive status are analyzed, with the purpose of inferring on the status of these populations and their possible condition of resident in these canals. In canals, its diet includes a greater number of different taxa as well as total number of preys consumed in comparison with the river populations, including items of greater biomass, such as lumbriculides. The selectivity analysis showed that T. areolatus prefer prey items like Chironomidae, Baetidae, Elmidae, Plecoptera and Hyallela. Although both the river as well as canal populations show an isometric type growth, they reach greater body lengths and weights in the latter. According to the reproductive states analysis in different periods of the year, populations inhabiting canal environments reproduce synchronically with those of the river, although these latter tend to show a slight delay in the reproductive activity. Rev. Biol. Trop. 53(1-2): 195-210. Epub 2005 Jun 24.
Anthropogenic modifications to aquatic ecosystems have altered connecting pathways within, and in some cases, between watersheds. Human structures, such as hydroelectric facilities, often impede fish migrations and may inflict heavy mortality on fish that become impinged or entrained. Conversely, an increase in connectivity between two waterways (e.g., through the construction of shipping canals, increased boat traffic) often results in an elevated risk of invasive species introductions. Non-physical barriers, which obstruct fish from an undesirable location without influencing the waterway, are one management approach to protecting valuable fish stocks and deterring biological invasions. Because many methods of behavioral deterrence have been employed against fish, there is a need to summarize and compare existing and developing technologies. This review details the use and application of electrical, visual, acoustic, chemical, and hydrological deterrence techniques that may be used to prevent fish movements. Site requirements are discussed, and a critical assessment of benefits and limitations to each technique are given. Because no single method of fish deterrence is “one size fits all”, this review to non-physical fish barrier technology will benefit managers and researchers attempting to develop a best-fit strategy on a case-by-case basis.
Recent large wildfires in western states have fueled increasing concerns of resource managers and the public about the effects of fire, including risks to fish, particularly endangered species. However, there are few empirical studies on the response of fish to fire and none that include anadromous species. The Tower Fire was one of four large fires in the upper John Day River basin in Oregon in 1996. Much of the area burned at moderate to high severity, consistent with the pattern of increasing fire severity and size projected for the region. Intense spring storms in 1997 and 1998 triggered large floods, landslides, and debris torrents that affected streams within and downstream of the fire. We investigated the effects of the fire and ensuing floods on fish distribution and abundance in three streams immediately after the fire through 2003. Immediately after the fire, no fish were found in moderate- and high-intensity burn areas. Fish began to repopulate defaunated reaches the year after the fire, and within 4 years distribution of juvenile steelhead (anadromous rainbow trout Oncorhynchus mykiss) and resident rainbow trout was similar to that before the fire. Juvenile spring Chinook salmon O. tshawytscha also began to use lower reaches of one of the streams after the flood, which had eliminated a culvert near the mouth of the stream suspected to be a barrier. Densities in most burned reaches and in unburned reaches downstream of the fire have rebounded to levels similar to or greater than densities in reference streams outside of the fire. An isolated introduced population of brook trout Salvelinus fontinalis also recovered. Thus, despite the size and severity of the fire, postfire hydrologic events, and human-induced changes to watersheds, fish populations were highly resilient.
The magnitude of hydropower developments in emerging regions threatens the sustainability of their riverine landscapes. Fragmentation of river networks by multiple barriers and the imposition of new hydrological regimes influences the ability of these river ecosystems to absorb and adapt to these developments and other stressors. Direct transfer of paradigms built from a restricted geographical base to a global context is fraught with issues because of regional differences in eco‐hydro‐geomorphology, biological communities, and nonlinear interactions between the two. In this manuscript, some impacts of hydropower development on Chilean riverine ecosystems are presented. To understand the context of hydropower, we provide the political context of energy development in Chile. Interactions between hydropower generation and Chilean river ecosystems with special reference to native Chilean fish fauna are outlined. Three case studies are presented that considers: (a) habitat alteration downstream of the Rucúe Dam, (b) the effects of daily hydropeaking in the Biobío River, and (c) mitigation strategies to reduce habitat alteration upstream of the San Pedro Dam. These case studies illustrate the expanding scientific knowledge on Chilean riverine landscapes. Finally, new measures to reduce ecosystem impacts of hydropower development on native Chilean fish communities are outlined. Although specific scientific information is available, developing regional ecohydrological models and improving knowledge of ecosystem and sustainability science is required. The scientific approach on which solutions are sought to address present and future river ecosystem problems in Chile are inherently interdisciplinary nature.
Adequately designed vertical slot fishways (VSF) mitigate the impact of anthropogenic obstructions onfish migrations. Until now, most studies on VSF were conducted focusing on high priority species, partic-ularly salmonids, while other species, such as cyprinids, have received less attention. In Mediterraneanrivers, where water availability is a problem, effective low discharge fishways are desirable. Attemptingto contribute towards filling this gap, the present study focuses on the behaviour and passage perfor-mance of two Iberian cyprinids with different ecological traits, the Iberian barbel (Luciobarbus bocagei,Steindachner, 1864) and the Southern Iberian chub (Squalius pyrenaicus, Günther, 1868). Fish passageperformance was investigated in a full-scale experimental VSF under two different slot configurations(C1 and C2), which require different discharges for equal mean water depths in the pools (Q = 110 L s−1, forC1, and Q = 81 L s−1, for C2). Results show that the chub, a small-bodied fish that utilises the upper portionof the water column, performed a higher number of upstream movements in C2, while for the barbel, alarge-bodied potamodromous bottom-oriented fish, the performance was similar in both configurations.With similar overall passage success, slot configuration C2 requires a lower discharge to operate, makingit the more cost-effective geometry, especially in regions affected by water scarcity.
Longitudinal river fragmentation through physical barriers is a major issue for the conservation of aquatic species in regions with intense hydropower development, such as Chile. The construction of fishways is the main mitigation strategy for maintaining connectivity for fish but development of designs suitable for a broad range of species is challenging. Recent work has shown that two species native to Chile, Cheirodon galusdae and Basilichthys microlepidotus exhibited similar swimming performance in free flow in the laboratory, indicating that a single fishway design may be suitable for both species. However, in the complex, three-dimensional altered flows observed in fishways, swimming performance is likely to vary from the free flow case due to the adoption of distinctive swimming gaits, variation in swimming styles, and the potentially destabilizing effects of wake vortices. In order to improve criteria for hydraulic design of fishways for multiple species we study the behavior and tail beat kinematics of C. galusdae and B. microlepidotus (juveniles), in the wake of vertical and bottom-mounted cylinders in an open channel flow. Cheirodon galusdae swam using a burst-and-coast style. This species avoided the cylinder wakes, searching for more favorable flow conditions. Basilichthys microlepidotus adopted a Kármán gait-like swimming strategy to swim in the cylinder wake. Tail beat frequency was constant in all experiments for both species, but in the presence of cylinders >2 cm in diameter, C. galusdae diminished the duration of the coast phase evidencing a higher propulsive effort. Tail beat amplitude of both species increased with the vortex length scale and decreased linearly with vortex shedding frequency. The fish Strouhal number correlated well with the relative vortex size and shedding frequency, compiling the swimming effort of species with very different behaviors, indicating that it is a suitable criterion for fishway design.
River fragmentation due to artificial barriers directly impacts fish communities by limiting migratory movements. This work aims to understand how small barriers affect the movements of a potamodromous cyprinid species – the Iberian barbel (Luciobarbus bocagei (Steindachner, 1864)) – in a 5.6 km upstream segment of a stream impacted only by the presence of physical barriers. Fish were marked with Visible Implant Elastomer tags (VIE), and barriers were seasonally characterized. A total of 683 fish were tagged, with 104 recaptures, during five sampling seasons (spring 2012 – early summer 2013). Eleven of the recaptured fish moved past a barrier, without any preference in terms of direction of movement. There were no differences in length, either between migrants and residents, or between upstream and downstreammigrants. The results show that although barbel are able to negotiate small barriers, part of the population did not move between fragmented reaches – an indication that under such conditions, fish species populations may adjust their life-history strategy to augment residency as it was hypothesized from the results.
Over recent years, there has been increasing challenge to the accepted wisdom that the environmental impacts of river engineering can be adequately mitigated through the installation of infrastructure, such as fish passes. This has led to a debate on the value of fish passage with some arguing that increased research and development will advance solutions for a variety of structures that are suitable for multiple species and transferable to different regions. Others suggest that policies and management strategies should reflect the realization that current mitigation technology frequently fails and can itself have negative impacts. Meta-analyses of the results of studies on fish passage effectiveness have led to the challenge of conventional views by highlighting lower than expected efficiencies, wide variation between and within fish pass designs, and bias towards consideration of a limited number of commercially important species mainly from northern temperate regions. Results of meta-analyses can also be controversial, and difficulties can arise when nuances associated with individual studies are lost and when metrics used are not standardized. Intrinsic variation in fish passage efficiency between and within species due to differences in patterns of movement and motivation may not be considered, and in many situations, current metrics are not appropriate. Quantification of variation in trends in fish passage efficiency over time and with spatial scale is lacking and should be the focus of future reviews. It is time to accept that fish passage does not provide a universally effective mitigation solution, particularly when designs and strategies are transferred to other regions and species for which they were not originally designed. Admitting to cases of failure is an essential first step to advancing water resources planning and regulation based on well-informed decision-making processes. Copyright
Umbrella species are employed as conservation short- cuts for the design of reserves or reserve networks. However, empirical data on the effectiveness of umbrellas is equivocal, which has prevented more widespread application of this conservation strategy. We perform a novel, large- scale evaluation of umbrella species by assessing the potential umbrella value of a jaguar (Panthera onca) conservation network (consisting of viable populations and corridors) that extends from Mexico to Argentina. Using species richness, habitat quality, and fragmentation indices of ~1500 co- occurring mammal species, we show that jaguar populations and corridors overlap a substantial amount and percentage of high- quality habitat for co- occurring mammals and that the jaguar network performs better than random networks in protecting high- quality, interior habitat. Significantly, the effectiveness of the jaguar network as an umbrella would not have been noticeable had we focused on species richness as our sole metric of umbrella utility. Substantial inter- order variability existed, indicating the need for complementary conservation strategies for certain groups of mammals. We offer several reasons for the positive result we document, including the large spatial scale of our analysis and our focus on multiple metrics of umbrella effectiveness. Taken together, our results demonstrate that a regional, single- species conservation strategy can serve as an effective umbrella for the larger community and should help conserve viable populations and connectivity for a suite of co- occurring mammals. Current and future range- wide planning exercises for other large predators may therefore have important umbrella benefits.
Hydropower barriers are among the most conspicuous anthropogenic alterations to natural riverine connectivity, resulting in species-specific effects linked to dispersal abilities, especially swimming performance. They may present a particular problem for small-bodied 'non-sport fish', such as those that characterize the freshwater communities of temperate regions in the Southern Hemisphere. Recent studies have suggested that nature-like fishways could ensure passage of diverse fish assemblages through hydropower barriers. Through experiments performed in a swim tunnel, we present, for the first time, fishway design criteria for two non-sport species endemic to Chile, a country experiencing rapid hydropower development. In`cremental velocity tests showed that Cheirodon galusdae and juveniles of Basilichthys microlepidotus were capable of very similar standardized critical swimming speeds of 69.7 and 69.6cms-1, respectively. When expressed in units of body lengths, C. galusdae was capable of very high critical speeds of 16.2bls-1, whereas for B. microlepidotus, this was 7.6bls-1. However, fixed velocity tests revealed that the swimming endurance of the latter species was slightly higher. Dimensionless analysis showed a clear relationship between fatigue time and fish Froude number, similar to that already described for subcarangiforms. Based on these results, we present fishway design curves indicating a transition from sustained to prolonged swimming at a fishway length of 15m. Our results show that the swimming capacity of these species is well-suited to the mean flow velocity field described for nature-like fishways. However, more work is required to understand the effects of turbulence on the passage of non-sport species.
Globally, rivers directly support a large proportion of the human population and provide ecosystem services essential for quality of life, including the provision of protein through maintenance of fisheries. Many systems have been extensively engineered to support agricultural production, urbanization and industrialization, activities that can negatively affect ecosystem processes, with some of the most profound impacts due to impoundment and flow depletion. Environmental impacts include disruption of flow and sediment regimes; degradation and fragmentation of physical habitat; alteration of water chemistry, temperature and dissolved gases; disconnection of energy and nutrient transfer in longitudinal, lateral, vertical and temporal dimensions and associated reductions in productivity; direct and indirect mortality of aquatic biota as a result of interactions with river infrastructure. Despite often well-developed and long-term recognition that impoundment and abstraction negatively impact ecology, the complexity of the mechanisms that drive these responses often remains poorly understood and requires further investigation. Similarly, despite considerable efforts to develop environmental impact mitigation strategies (e.g. methods to assign appropriate environmental flows) and technology (e.g. fish passes and screens), partial solutions frequently fail to fully compensate for negative effects experienced and in some cases are themselves damaging. This chapter reviews the impacts of impoundments and water offtakes on freshwater fish populations and discusses the mitigation options currently available. Biases and gaps in understanding are identified, and recommendations for the future made. In the face of unprecedented future demand, it is argued that mitigation alone will be insufficient to sustain important populations of fish and that there is a need for society to discuss the need to better manage demand on resources based on more realistic valuation of existing ecosystem services.
Protecting the worlds freshwater resources requires diagnosing threats over a broad range of scales, from global to local. Here we present the first worldwide synthesis to jointly consider human and biodiversity perspectives on water security using a spatial framework that quantifies multiple stressors and accounts for downstream impacts. We find that nearly 80% of the worlds population is exposed to high levels of threat to water security. Massive investment in water technology enables rich nations to offset high stressor levels without remedying their underlying causes, whereas less wealthy nations remain vulnerable. A similar lack of precautionary investment jeopardizes biodiversity, with habitats associated with 65% of continental discharge classified as moderately to highly threatened. The cumulative threat framework offers a tool for prioritizing policy and management responses to this crisis, and underscores the necessity of limiting threats at their source instead of through costly remediation of symptoms in order to assure global water security for both humans and freshwater biodiversity.
Recent efforts to improve the survival of hydroelectric turbine-passed juvenile fish have explored modifications to both operation and design of the turbines. Much of this research is being carried out by power producers in the Columbia River basin (U.S. Army Corps of Engineers and the public utility districts), while the development of low-impact turbines is being pursued on a national scale by the U.S. Department of Energy. Fisheries managers are involved in all aspects of these efforts. Advanced versions of conventional Kaplan turbines are being installed and tested in the Columbia River basin, and a pilot scale version of a novel turbine concept is undergoing laboratory testing. Field studies in the last few years have shown that improvements in the design of conventional turbines have increased the survival of juvenile fish. There is still much to be learned about the causes and extent of injuries in the turbine system (including the draft tube and tailrace), as well as the significance of indirect mortality and the effects of turbine passage on adult fish. However, improvements in turbine design and operation, as well as new field, laboratory, and modeling techniques to assess turbine-passage survival, are contributing toward resolution of the downstream fish passage issue at hydroelectric power plants.
In this study, we assess global hydropower potential using runoff and stream flow data, along with turbine technology performance, cost assumptions, and consideration of protected areas. The results provide the first comprehensive quantification of global hydropower potential including gross, technical, economic, and exploitable estimates. Total global potential of gross, technical, economic, and exploitable hydropower are estimated to be approximately 128, 26, 21, and 16 petawatt hours per year, respectively. The economic and exploitable potential of hydropower are calculated at less than 9 cents/kWh. We find that hydropower has the potential to supply a significant portion of the world energy needs, although this potential varies substantially by region. Globally, hydropower potential is comparable to the total electricity demand in 2005. Hydropower plays different roles in each country owing to regional variation in potential relative to electricity demand. In some countries such as the Congo, there
Many species have fragmented distribution with small isolated populations suffering inbreeding depression and/or reduced ability to evolve. Without gene flow from another population within the species (genetic rescue), these populations are likely to be extirpated. However, there have been only ~ 20 published cases of such outcrossing for conservation purposes, likely a very low proportion of populations that would potentially benefit. As one impediment to genetic rescues is the lack of an overview of the magnitude and consistency of genetic rescue effects in wild species, I carried out a meta-analysis. Outcrossing of inbred populations resulted in beneficial effects in 92.9% of 156 cases screened as having a low risk of outbreeding depression. The median increase in composite fitness (combined fecundity and survival) following outcrossing was 148% in stressful environments and 45% in benign ones. Fitness benefits also increased significantly with maternal ΔF (reduction in inbreeding coefficient due to gene flow), and for naturally outbreeding versus inbreeding species. However, benefits did not differ significantly among invertebrates, vertebrates and plants. Evolutionary potential for fitness characters in inbred populations also benefited from gene flow. There are no scientific impediments to the widespread use of outcrossing to genetically rescue inbred populations of naturally outbreeding species, provided potential crosses have a low risk of outbreeding depression. I provide revised guidelines for management of genetic rescue attempts. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
We examined persistence (constancy of species composition) and stability (constancy of relative species abundances) of a fish assemblage at one site on a fourth-order stream in north-central Ohio. Thirty-eight quantitative samples taken over a 9 yr period indicate that the assemblage was both persistent and stable over that period. Analysis of trophic composition of the assemblage supports the same conclusion. Five groups of species were clearly identified based on clustering of persistence and numerical abundance patterns: permanent/high density, permanent/moderate density, frequent/moderate density, infrequent/low density, and transients. Although the assemblage has some degree of predictability, the mechanisms responsible must be evaluated through other than documentation of long-term pattern.
1. Restoring longitudinal connectivity is a key river restoration goal. This study tested the efficacy of a fish ramp and spoiler baffles for restoring indigenous fish communities upstream of a culvert.
2. Before–after monitoring showed that installation of the ramp and spoiler baffles increased species richness (mean increase 80%) and total fish density (mean increase 45%) upstream of the culvert.
3. Passage trials on the ramp and baffled culvert were carried out using inanga, Galaxias maculatus (Jenyns), a commonly occurring weak-swimming migratory fish. The trials showed that inanga were capable of successfully ascending both the ramp (overall 27.1% success) and culvert with baffles (overall 6.2% success) under the conditions tested (cf. 0% success for this species before retrofitting), but passage efficiency was still relatively low in both cases.
4. Retrofitting of culverts can therefore be effective for restoring upstream fish passage. However, to maximize effectiveness it is essential that restoration goals are well defined and retrofitting solutions are designed appropriately for the target species.
Quantifying fish dispersal and identifying its general predictors is key for understanding temporal patterns in population dynamics, emigration and immigration, meta-community dynamics, many ecological processes and predicting recovery time or population responses to environmental changes. This is the first comprehensive quantitative meta-analysis of heterogeneous freshwater fish movement, aiming to determine mobile and stationary shares of fish communities, their dispersal distances and key predictors of dispersal patterns. By reviewing and analysing 160 empirical data sets from 71 studies covering 62 fishes in streams, it goes beyond previous studies of salmonids’ heterogeneous movement. Based on fitted leptokurtic dispersal kernels, the movement distances of (i) a stationary component (σstat) and (ii) a mobile component (σmob) as well as the (iii) share of each component (p) were calculated. The median movement distance of the stationary and mobile component of a fish population was 36.4 and 361.7 m, respectively. The share of the stationary individuals was high (median = 66.6%), but unrelated to movement distance. Single and multiple linear regressions as well as mixed-effects models revealed movement distances positively related to fish length, aspect ratio of the caudal fin, stream size and duration of the study. Furthermore, movement distance differed between taxonomic families. The quantitative parameters of heterogeneous fish movement provided are prerequisite to estimate time lags in fish response to river rehabilitation, temporal patterns in species dispersal, and minimum effective size of potential founder populations for species conservation and stock recovery based on minimum numbers of specimen to disperse.
abstract: This is the third compilation of imperiled (i.e., endangered, threatened, vulnerable) plus extinct freshwater and diadromous fishes of North America prepared by the American Fisheries Society's Endangered Species Committee. Since the last revision in 1989, imperilment of inland fishes has increased substantially. This list includes 700 extant taxa representing 133 genera and 36 families, a 92% increase over the 364 listed in 1989. The increase reflects the addition of distinct populations, previously non-imperiled fishes, and recently described or discovered taxa. Approximately 39% of described fish species of the continent are imperiled. There are 230 vulnerable, 190 threatened, and 280 endangered extant taxa, and 61 taxa presumed extinct or extirpated from nature. Of those that were imperiled in 1989, most (89%) are the same or worse in conservation status; only 6% have improved in status, and 5% were delisted for various reasons. Habitat degradation and nonindigenous species are the main threats to at-risk fishes, many of which are restricted to small ranges. Documenting the diversity and status of rare fishes is a critical step in identifying and implementing appropriate actions necessary for their protection and management.