Brazil has more than 700 large reservoirs distributed in all of the major river basins of South America. Most dams were constructed to produce electricity. Although these reservoirs favor the ...development of local and regional economies, they seriously impact the aquatic biota. An unavoidable consequence is the change in the composition and abundance of species, with the proliferation of some and reduction or even local extinction of others. The intensity and nature of these changes are related to peculiarities of the local biota and the location, morphometric and hydrological characteristics of the reservoir, dam operation and interactions with other uses of the basin, including other reservoirs. These impacts exhibit substantial spatiotemporal variations. The filling phase is marked by abrupt and intense changes in the key attributes of aquatic habitats, followed by predominantly heterotrophic processes, with possible thermal stratification and anoxic conditions. Fish richness increases soon after filling and decreases in subsequent years. Trophic depletion is expected, and diversity gradients are intensified toward more lentic stretches, the average length of fish decreases, and the fish fauna becomes dominated by species with sedentary strategies and/or parental care. The virtual absence of species with pre-adaptations to inhabit lentic areas of large reservoirs leads to a concentration of biomass in shallow littoral areas. Long-distance migratory species are the most affected, which include larger fish with high market value. Migratory species require different biotopes to fulfill their life cycles and strongly depend on the seasonal flood regime, which is altered due to dam operation. In this study, we discuss the details of these trends as well as the mitigation measures and management actions that are practiced in Brazil. We conclude that these actions have not promoted the conservation of fish; on the contrary, some of them have generated additional impacts. As a consequence, the conservation of Neotropical fish and aquatic resources is severely threatened.
Aim of the study: The aim of the work is to determine the work of a pool pass located on the Dłubnia River and attempt to determine repair recommendations that will work properly and will not be an ...obstacle for migrating fish. Material and methods: Field work. Identification of passages elements that may limit fish flow based on standards that give typical geomteric dimensions. An attempt to determine its repair. Results and conclusions: The fish pass is not working properly. The work presents repair recommendations.
The meander‐type fish pass is a slotted fishway characterised by the exclusive use of rounded and smooth components. Due to the specific geometry and arrangement of the basins, which differ ...considerably from the conventional vertical slot pass, there are significantly different hydraulic conditions. The water flow is guided along the basin walls by means of a dominant main current while the water body is much calmer towards the centre of the basin, where very low flow velocities are found. A detailed assessment of the functionality is currently impossible due to the small number of surveys of fish passage hitherto carried out. However, considerable potential is indicated by the high passage rates at some sites and the lack of selectivity with regard to species and small fish, together with the design advantages and the adaptation possibilities after construction work is completed. In this study, we offer some recommendations for dimensioning to enable this potential to be exploited. These are oriented around recommendations for conventional vertical slot passes regarding basin size, flow depth and slot width. Due to the great potential of the meander‐type fish pass, it is desirable to construct still more individual pilot passes to implement comprehensive surveys of fish passage on a sound methodological basis.
This study aims to investigate the upstream movement patterns of potamodromous fish species using multi-annual monitoring of modern multi-species fish passes in two medium-sized Belgian rivers: the ...Berwinne and the Amblève. During a 6-year monitoring period including a frequency of 1–5 times per week, the captured individuals were identified, measured and weighed to determine species abundance, and the periodicity of their seasonal movement patterns was investigated in relation to environmental factors. In the Amblève, 22 different fish species were monitored (
n
= 1513 individuals; biomass of 154 kg) and 14 species in the Berwinne (
n
= 3720; 408 kg). In both fish passes, inter-annual differences were observed, but the first year of monitoring was the best in terms of biomass, indicating the existence of an opening effect just after the fish passes opening, which allowed new migration routes. Salmonids and rheophilic cyprinids were predominant in terms of biomass, while minnow and spirlin were predominant in terms of number of fishes. The diversity in size ranged from 46 to 760 mm demonstrating the importance of movements in various life stages. The capture periodicity showed different mobility patterns between the adult and juvenile stages in most species. Movements occurred frequently during the circum-reproduction period for some species, but many species moved also apart from spawning period. This study highlights the omnipresence of patrimonial holobiotic potamodromous fish at different life stages that reflect their biological needs to move throughout the annual cycle. They must be considered as target species in river continuity restoration programmes and fish-pass design.
Flow Simulation in a Rock-Ramp Fish Pass Baki, Abul Basar M; Zhu, David Z; Rajaratnam, Nallamuthu
Journal of hydraulic engineering (New York, N.Y.),
10/2016, Letnik:
142, Številka:
10
Journal Article
Recenzirano
AbstractThe flow characteristics in a rock-ramp fish pass can be significantly altered by the boulder arrangement. This study used a three-dimensional computational fluid dynamics solver to ...investigate flow characteristics for variations of discharge, channel slope and boulder size, spacing, and pattern. This study derived relationships for estimating water depth and velocity in a rock-ramp fish pass as a function of discharge and structure geometry. The flow resistance varies significantly with emergent boulder spacing and is nearly constant for submerged boulders. This study derives relationships for the drag coefficient and submergence ratio to forecast average flow velocity using a flow-resistance equation. Based on maximum velocity and a slow velocity zone, this study recommends effective boulder spacing in the longitudinal and transverse directions for two different boulder patterns. Finally, this study developed a design procedure for designing a rock-ramp fish pass.
Habitat fragmentation is a principal threat to biodiversity and artificial river barriers are a leading cause of the global decline in freshwater biota. Although the impact of barriers on diadromous ...fish is well established, impacts on river‐resident fish communities remain unclear, especially for low‐head barriers.
We examined the movement of five contrasting freshwater fish (topmouth gudgeon, European minnow, stone loach, bullhead and brown trout) in an experimental cascade mesocosm with seven pools separated by small vertical barriers.
Passage rates differed significantly among species and increased with body size and sustained swimming speed (Usus), ranging from an average of 0.2 passes/hr in topmouth gudgeon to 3.4 passes/hr in brown trout. A random‐walk simulation indicated that barriers can result in net downstream movement and shifts in community composition.
Passage rates in brown trout were leptokurtic, that is, most individuals were relatively sedentary while a small proportion showed frequent movements. Upstream passage rates of brown trout increased with body length and boldness while fish with lower aerobic scope tended to move downstream. Passage rates showed significant individual repeatability in brown trout, independent of body size, indicating the potential for in‐stream barriers to exert selective effects on fish populations.
Our results show that barrier effects can be more complex than simply blocking fish passage, and that river‐resident fish can be impacted even by very small barriers. We show that fish passage depends on a wide range of morphological, physiological and behavioural drivers, and that barriers can exert selective effects on these traits and cause shifts in community composition.
Policy implications. Barrier mitigation measures need to embrace interspecific and intraspecific variation in fish passage to avoid inadvertent artificial selection on fish communities. Given the high abundance of low‐head structures in river systems worldwide, a paradigm shift is needed to recognise the subtle impacts of small barriers on freshwater biodiversity. Removal of small barriers or nature‐like fishways should allow better passage of the wider fish community compared to widely used salmonid‐centric fish passage options.
Barrier mitigation measures need to embrace inter‐ and intraspecific variation in fish passage to avoid inadvertent artificial selection on fish communities. Given the high abundance of low‐head structures in river systems worldwide, a paradigm shift is needed to recognise the subtle impacts of small barriers on freshwater biodiversity. Removal of small barriers or nature‐like fishways should allow better passage of the wider fish community compared to widely used salmonid‐centric fish passage options.
Fish passes are essential elements for maintaining continuity for migrating fish. Without them, fish would be unable to undertake migration to satisfy their basic life needs. These devices must meet ...a range of requirements related to the size of individual fish pass elements and the hydrodynamic parameters of the flowing water. Despite efforts, it is not always possible to meet these requirements. There are many causes of errors in the design and construction of fish passes, and each case should be assessed individually. The most severe consequence of these errors is the obstruction of fish migrating upstream. In this study, an analysis of the permeability of a semi-natural fish pass was conducted for fish. This assessment was carried out using two methods. In the first approach, the required geometric dimensions of the fish pass elements were determined based on the dimensions of individuals living in the river channel. In the second approach, the dimensions were extracted from publications dedicated to slot fish passes, as the studied object resembles such a design. The analysis revealed that the fish pass does not fulfil its intended role. All fish species living in the Nidzica River channel face difficulties in passing through the fish pass, including the brook trout, for which the object is specifically designed. The main errors stem from the design and construction, resulting in exceeded values, primarily in the hydrodynamic parameters, rendering the fish pass impassable. The study also aimed to develop corrective recommendations considering the latest scientific developments.
Fish larval drift is an essential step in the life cycle of riverine fish species as it determines dispersal and colonisation. Anthropogenic flow alterations and interruption of longitudinal and ...lateral connectivity by river damming and straightening can severely affect larval drift patterns. In this study, we characterised spatio‐temporal drift patterns of fish larvae in the heavily regulated large alpine River Inn and within a constructed nature‐like fish bypass.
Drift was investigated in the main reproduction period of the fish fauna in this river, ranging from mid‐April to end of June. Diel patterns were assessed by samples taken during day, dusk, night, and dawn each day of sampling. To obtain robust species identification, we used DNA barcoding for genetic verification of phenotypically pre‐sorted groups.
From a total of 1,069 fish larvae and 283 fish eggs caught, DNA barcoding revealed 16 species from five families, including several target species of conservation. We found strong evidence that several endangered species, such as Chondrostoma nasus, Thymallus thymallus, Cottus gobio, and Aspius aspius successfully reproduced in the bypass system. Genetic species verification showed a high level of homogeneity in most phenotypically pre‐sorted groups.
Distinct seasonal patterns were observed, with the majority of fish species in the drift observed in mid‐June. Thymallus thymallus and Cottus gobio dominated larval drift at the beginning of the observation followed by mainly unimodal abundance peaks of several Cyprinid species. Nocturnal drift prevailed in all species.
Our results on the spatial occurrence and abundances of fish larvae highlight the importance of bypass systems in heavily modified waterbodies to provide valuable spawning habitats and drift corridors around dams. Moreover, the distinct species‐specific time patterns of larval drift represent a first basis to direct future discharge and river management plans in large alpine rivers towards a protection of the sensitive larval stages of specific target species of conservation. This includes bypass and turbine operation modes in the period of highest drift activity, as well as the construction of nature‐like bypass systems and creation of spawning grounds therein.
•The efficacy of a Larinier super active baffle fishway was measured for adult European river lamprey (Lampetra fluviatilis).•PIT and acoustic telemetry were used in two years, before and after ...placement of studded tiles along the inner fish pass wall.•Attraction efficiency was high in both years but passage efficiency was poor for unmodified (0.3%) and modified (7.1%) passes and number of attempts was high.•Passage directly over the weir was higher than through the fishway.•Current super active baffle fishways are unsuitable for river lamprey.
To help achieve effective longitudinal river connectivity, evaluation of the efficacy of fishway use by upstream-migrating fishes is needed. Larinier super active baffle (SAB) fishways are relatively cheap retrofit fish passes, suitable for low-head barriers, widespread in Europe and the most commonly fitted technical pass in Britain. Their suitability for non-salmonids, however, is poorly quantified. The efficacy of a 15% gradient SAB fishway and effects of flow regime and water temperature were tested for European river lamprey (Lampetra fluviatilis) using passive integrated transponder (PIT) and acoustic telemetry at a Crump weir on the River Derwent, Northeast England. In migration season 2013–14, over a wide range of flows, 90.1% of 350 tagged lamprey entered the fishway. One fish (0.3%) of those that entered the pass ascended successfully, even though measured water velocity was within laboratory-measured performance conditions for this species. Of 29 acoustic-tagged lamprey that visited the weir over the same period, four (13.8%) ascended it directly, during elevated flows. These data suggest that high turbulence and/or the physical characteristics of baffles may inhibit lamprey ascent of the pass. In migration season 2014–15, we tested the effect of adding studded modular plastic tiles adjacent to the fishway wall, employing PIT antennas separately interrogating the entrance and exit of each of the main fishway and tile routes. 85.8% (169) of 197 tagged lamprey entered the fishway, of which 72/169 (42.6%) entered the tile entrance. Passage efficiency of entrants was 7.1% (12/169), all of which used the tiled route. Reduced local flow velocity in combination with increased availability of resting habitat within the tiles may have facilitated increased passage. Although fishway passage efficiency increased after placement of the modular tiles, it remained half that measured for direct weir passage, both of which are inadequate for connectivity restoration. Quantitative tests of studded tiles placed on the sloping downstream weir face by comparison to control conditions may be more effective and are needed. This study demonstrates the importance of carrying out full-scale field tests to supplement possible solutions developed under laboratory conditions.
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