Effect of flow regime hydraulics on passage performance of Iberian chub (Squalius pyrenaicus) (Günther, 1868) in an experimental pool-and-weir fishway

Dams and weirs strongly affect or interrupt the longitudinal connectivity of rivers, by limiting the movements of several fish species while altering and fragmenting habitats. Fishways, especially pool-type fishways, are used to diminish this impact by enabling fish to negotiate barriers. The aim of this work is to study the behaviour of a small-sized resident cyprinid fish, the Iberian chub—Squalius pyrenaicus (Günther, 1868)—within a prototype of a pool-type fishway, equipped with both surface notches and bottom orifices, and experiencing two different flow regimes, plunging and streaming. Results show that the fish tended to be more successful in their upstream movements under streaming flow and that, for this regime, the surface notch was the preferred route for upstream movements. Flow velocity patterns corroborated the results, showing that the plunging flow regime may have driven fish downstream, while the streaming flow regime may have attracted fish upstream. The plunging flow also prevented access of this surface-oriented species to the surface notch, effectively reducing the area available for transport. Thus, the streaming flow regime can be a sound option for this and other small-sized species, as it enhances fish movements through the fishway.     

Performance of fish lift recently built at the Touvedo Dam on the Lima River, Portugal

From March 1998 to February 1999, upstream fish passage was continuously monitored by video tape analysis at the fish lift Touvedo Dam on the Lima River, northern Portugal. A total of 1194 individuals from seven species were transferred by the lift. Cyprinids were the dominant group collected, with Iberian nase Chondrostoma polylepis (Steindachner) (31.8%) being the most abundant species, followed by Iberian barbel Barbus bocagei (Steindachner) (21.1%), Iberian dace Leuciscus carolitertii (Doadrio) (19.2%) and Iberian red roach Rutilus arcasii (Steindachner) (7.1%). Brown trout Salmo trutta fario (L.) and European eel Anguilla anguilla (L.) accounted for 10.8%, whereas Atlantic salmon Salmo salar (L.) was rarely observed. Most cyprinid seasonal movements were observed in the spring and were associated with reproduction. The timing of the run varied and its beginning appeared to be mainly dependent on water temperature. Roach, dace and nase used the fish lift intensively from mid-April until the end of summer. Barbel use of the lift intensified in mid-May in association with warmer water. Salmonids migrated in June–July and autumn. Significant differences were not found in hourly activity, except for nase and barbel, in June and July, respectively. Fish passage was not related to river discharge. The relative effectiveness of the fish lift is discussed in relation to the various species.     

Diel pattern of fish presence at the Changzhou fishway (Pearl River,China) during the flood season

Restoration of fish populations is required in China with the use of fishways at dammed rivers, but scant biological data is available for their design and operation. The Changzhou fishway (CFW) on the Pearl River is the largest in China, providing a channel for multispecies upstream migrations. This preliminary study used a combination of fish traps and hydroacoustic detection to document the diurnal presence of fish in the CFW, with the purpose of providing essential data for a future, solid performance of this fishway. Eighteen species from a total of 1362 fish individuals were collected in the traps. Three species were dominant, namely, Squaliobarbus curriculus, Pseudobagrus vachellii and Cirrhinus molitorella, altogether sharing proportions of 74.70 and 76.26% in the daytime and nighttime, respectively. Balanced by the up‐/downward movements of each fish, they entered the fishway with net numbers of 339.9 ± 113.4 ind.h^?1, and exited with net numbers of 234.54 ± 26.66 ind.h^?1. In diel fishway use, no significant differences were observed in either species composition or individual size during a diurnal period. Fish presence at the monitored sites within the fishway was recorded primarily during the daytime, showing a particular trend towards crepuscular use at the entrance and an uninterrupted use at the exit. This initial study showed a significant fish presence in the CFW during the flood season; the outcome of the study will be the basis of future research aimed at evaluating the passage efficiency of the CFW and the use thereof in other seasons.     

Effect of two flow regimes on the upstream movements of the Iberian barbel (Luciobarbus bocagei) in an experimental pool‐type fishway

Literature related to pool‐type fishways has seen a recent upsurge of interest in the placement of instream structures for improving fish passage. However, there is still no information on how different flow regimes created by boulder placement have an influence on upstream fish movements. The main goal of this study was to assess the performance of two different flow regimes, characterized by the relative depth of flow (d/h), where d is the water depth and h is the height of artificial bottom substrata, in assisting fish passage in an experimental full‐scale pool‐type fishway. Two series of experiments consisting of 20 replicates each and representing distinct flow regimes created by boulder placement in the flume bottom – d/h > 4 (regime 1) and 1.3 < d/h < 4 (regime 2) – were carried out to analyse the proportion and timing of successful upstream movements of a potamodromous cyprinid, the Iberian barbel (Luciobarbus bocagei). Although no significant differences (P > 0.05) in passage success were observed between regimes (55% and 60%, respectively), fish transit time was significantly lower (P < 0.05) in regime 2 (mean ± SD: 2.6 ± 1.6 min.) than in regime 1 (7.1 ± 5.8 min.). The results of these experiments show that lower relative depths can be more beneficial to fish passage because they reduce the transit time for successful negotiation, thus providing a useful indication on how to improve fish passage through pool‐type fishways.     

Habitat quality affects the condition of Barbus sclateri in Mediterranean semi-arid streams

We investigated the site level relationships between fish condition and environmental variables in Sclater's barbel, Barbus sclateri, from semi-arid streams in the south-eastern Iberian Peninsula. These freshwater ecosystems are characterized by strong seasonal fluctuations in flow levels (droughts and floods) as a consequence of their irregular hydrological regime on both an annual and pluriannual scale. We analysed the relationships between 11 ecosystem variables [conductivity, oxygen concentration, water temperature, pH, seasonal water flow, dominant substrate, submerged vegetation, QBR (Riparian Ecosystems Quality Index), BMWP' (Spanish version of the Biological Monitoring Working Party), fish refuge index and fish density] and fish condition by comparing mass–length relationships of nine populations of Sclater's barbel located in five sub-basins with different environmental conditions. Fish condition differed between the populations studied and was mainly dependent on the ecological variables related with water flow and, consequently, the physical structure of the streams, which is directly related to substrate and fish refuge.     

Effects of a flow-gauging weir on the migratory behaviour of adult barbel, a riverine cyprinid

Barbel Barbus barbus exhibited substantial movements in the River Nidd between March and July 1994, with some individuals moving nearly 20 km upstream, although there was considerable individual variation. Most upstream movement occurred during May. Fifteen of the 23 fish tracked attempted to pass the weir, and of these six were successful. Barbel tended to approach the weir around dusk and dawn, reflecting observed patterns of localized activity, or at night, but crossed the weir only at night. Those fish which crossed the weir moved substantial distances upstream to spawn, while those that were unsuccessful moved down-stream. The weir delayed the net upstream progress of all adult barbel. Successful traversal was not closely related to flow or water temperature conditions. The study emphasizes the impact of relatively minor obstructions on the natural migrations of barbel.     

Assessment of a vertical slot fishway in south‐eastern Australia designed to pass numerous species and size classes of fish

In the Barwon River, Australia, a tidal barrage formed a major impediment to fish movement so in 2013 a vertical slot fishway was installed. The assessment of fishways on tidal barriers is rare in Australia so to ensure the fishway was achieving its ecological objective (i.e. successfully passing the target size range of fish of 20–400 mm total length), fish were trapped at the entrance and exit on 12 occasions and the species composition, abundance and length of fish at the two locations were compared. Additionally, a section of the river downstream of the fishway was sampled to ensure fishway trapping accurately reflected the species composition wanting to use the fishway to move upstream. Eighteen species and 69,246 individual fish were caught in the fishway traps. Catch rates between locations did not differ for Common Galaxias (Galaxias maculatus) or Australian Smelt (Retropinna semoni), although species‐specific catch rates were lower at the exit for Flat‐headed Gudgeon (Philypnodon grandiceps), Tupong (Pseudaphritis urvillii) and Yellow‐eye Mullet (Aldrichetta forsteri). Length distribution between locations only differed for Australian Smelt with small fish under‐represented at the exit location (<25 mm total length). Eight species of fish were collected downstream of the fishway that were not collected in it; however, all of these were estuarine dependent except the non‐native Common Carp (Cyprinus carpio). Our results indicate that vertical slot fishways are a suitable design for improving river connectivity at a low head, tidal barrages in south‐eastern Australia. The study reiterates the importance of reinstating connectivity for species with obligate marine/freshwater migratory life history traits, and the indirect benefits of increased productivity made available to upstream areas.     

Phylogeography and the genetic structure of the land-locked freshwater prawn Macrobrachium asperulum (Crustacea: Decapoda: Palaemonidae) in Taiwan

Millions of fish ascend through fishways in South America every year, but there is no evidence that downstream passage is occurring in large dams. Based on this concern, this study monitored the fish ladder at Lajeado Dam, Tocantins River, a large Amazonian tributary. To investigate the extent of downstream movements through the fishway, ascending and descending movements were quantified between November 2007 and October 2008. Monitoring showed that the ladder is restrictive to many species in both directions, but downstream passage was much more limited: almost all fish captured in the ladder (99.5%) were ascending the facility. Consequently, the numerical ratio between ascending and descending fish (ind./m²) showed high positive values throughout the year (1508:1 on average); migratory species showed higher ratios. All results showed that downstream passage through the ladder is very limited, and that the facility allows only one-way movements (i.e., upstream). This is the first empirical evidence showing that a ladder is critically deficient for downstream passage of fishes in South America.     

Habitat quality affects the condition of Luciobarbus sclateri in the Guadiamar River (SW Iberian Peninsula): effects of disturbances by the toxic spill of the Aznalc��llar mine

This study analyzes the somatic condition of southern Iberian barbel Luciobarbus sclateri (Günther, 1868) in the Guadiamar River (SW Iberian Peninsula). This river was seriously affected by a toxic spill of about 4?million cubic meters of acidic water and 2?million cubic meters of mud rich in heavy metals. Once the spill removal works concluded, sites affected and unaffected by the accident were sampled to study its effects on the fish fauna. The ecological variables registered were related to water quality, physical state of reaches, ecological quality, resources exploited by fish, and potential intra-specific interactions. From an initial 15 ecological variables, seasonal water flow and pH explained most of the variation in barbel condition. This study shows that the Guadiamar River, 56?months after the accident, is still undergoing a recovery process where, beyond ecological variables, proximity to the affected area is the most influential factor for fish condition.     

Fish passage design for sustainable hydropower in the temperate Southern Hemisphere: an evidence review

The development of hydropower and other infrastructure that disrupts river connectivity poses a serious threat to highly endemic and genetically distinct freshwater fish species in temperate parts of the Southern Hemisphere. Such locations have been neglected in previous reviews on fish passage. Fishways have long been constructed to mitigate the impacts of riverine barriers on fish, yet they have often failed for all but the largest, strongest swimming taxa. This is a particular problem in the temperate south, which is home to native species that are non-recreational and generally small-bodied with weak swimming abilities (e.g. Galaxiidae) relative to typical target species for fishway design (e.g. Salmonidae). Using the Eco Evidence method for rapid evidence synthesis, we undertook an assessment of evidence for effective fishway design focusing on species representative of the temperate south, including eel and lamprey. Systematic literature searches resulted in 630 publications. Through a rigorous screening process these were reduced to 46 publications containing 76 evidence items across 19 hypotheses relating to design criteria for upstream and downstream passage. We found an overwhelming lack of evidence for effective fishway design in the temperate south. Particular deficiencies were found with regard to the design of effective facilities for downstream passage. The attraction and entrance of upstream migrating fish into fishways is also relatively under-researched. Given the urgent need for effective fishways in the temperate south, these results justify an approach to fishway design based on a combination of empirical data and expert knowledge. In the meantime, significant resources should be assigned to improve the evidence base through high quality research. The particular deficiencies identified here could guide that research agenda.     

Monitoring fish passes using infrared beaming: a case study in an Iberian river

An application of a new automated fish counting device – the Riverwatcher System (RW) – was used to monitor upstream fish movements in a pool‐and‐weir fish pass in the River Zêzere, Portugal, for 141 days from June 2002 to May 2003. Fish populations were also collected downstream using multimesh gillnets (5 different mesh sizes ranging from 30 mm to 85 mm knot to knot; ratio between mesh sizes of about 1.30) and electrofishing for comparison with fish records produced by the RW. More than 3000 individual Iberian nase Chondrostoma polylepis ascended the fish pass and moved through the RW during the study period. However, only 18% of the records produced by the RW contained silhouettes similar to fish; no individual smaller than 15 cm TL was recorded by the counter. Most seasonal movements (73.9%) occurred in spring and were associated with reproduction. Displacements seemed to occur independently of time of day. Water temperature (range: 12–22°C) was the only significant environmental variable (P < 0.01) influencing upstream movements of this species. Further development of hardware and software will be necessary to improve performance of the counter, particularly in Mediterranean rivers, where more turbid waters and a greater proportion of small‐size species are present.     

Comparison of fish communities between above‐ and below‐dam sections of small streams; barrier effect to diadromous fishes

To analyse the effects of small‐scale dams on fish communities, species diversity, population density, biomass, migration over dams and trophic relationships were investigated in the above‐ and below‐dam sections of three Japanese streams. The dams were 1·5–3·9 m high, constructed within 400 m of the sea, and had no impoundment or fishway. Fish communities were mainly composed of diadromous fishes. Of the 17 species sampled, only a few species of gobies, Rhinogobius spp. and Gymnogobius spp. were able to climb and migrate upstream over the dams. Consequently the number of species, and total density and biomass of fishes below the dams was high, but low above the dams. One of the most dominant fish below dams, Plecoglossus altivelis altivelis , predominantly fed on benthic algae, whereas other fishes preyed on benthic invertebrates. Trophic relationships above dams were very simple, the few species of gobies preying on chironomid larvae and other aquatic invertebrates.     

溪流鱼类群落对低水头坝的大小及功能的响应——以皖南山区河源溪流为例

以皖南山区的河源溪流为研究区域, 根据2016年7月和11月两次的调查数据, 在区分土著物种和本地入侵物种的基础上, 初步比较研究了低水头坝的坝上蓄水区和冲刷区鱼类群落的季节动态及所受水坝大小和功能的影响。共采集鱼类24种, 隶属4目10科, 其中土著鱼类13种, 本地入侵鱼类11种。尽管坝下冲刷区的鱼类群落无显著季节变化, 但坝上蓄水区的鱼类群落季节动态显著, 其中11月的鱼类个体数显著高于7月。水坝大小对鱼类群落的影响相对较小, 仅冲刷区入侵鱼类群落结构随水坝大小显著变化; 水坝功能对鱼类群落的影响较大, 蓄水区土著鱼类群落及冲刷区入侵鱼类群落等都随水坝功能显著变化——同蓄水坝相比, 引渠坝的蓄水区中宽鳍鱲较少但中华花鳅和吻虾虎鱼较多, 且引渠坝的冲刷区中高体鳑鲏和泥鳅具有更高多度。研究表明, 在研究区域内, 低水头坝对鱼类群落分布的影响视水坝蓄水功能而不同, 而水坝大小的相对重要性较低。研究也进一步证实, 因亲流性土著鱼类与广布性入侵鱼类对低水头坝干扰的响应不同, 在开展有关人类活动对溪流鱼类多样性的影响评价时, 有必要区分土著物种和入侵物种来进行, 以确保研究结论的科学性。     

Occurrence of cyprinids in fish ladders in relation to flow

To analyse the relationship between spawning migrations and flow, cyprinids from ten fish ladders of the Elbe River (Czech Republic) were collected during the period of spawning migrations (April–June) in 1996, 2000 and 2001. Number of species and individuals in the fish ladders increased with increasing flow up to medium values, followed by further decrease during high flows, whilst length of individuals increased with increasing flow. Moreover, occurrence of four the most numerous species (bleak, roach, silver bream and barbel) showed species specific differences in response to flow variability. In early spring, the highest number of bleak in fish ladders occurred during the low flow, whilst later increased with increasing flow. Occurrence of roach and silver bream achieved the maximum during the medium flow values across the whole studied period. In opposite, occurrence of barbel increased with increasing flows during the whole period. Furthermore, it can be assumed that occurrence of fish in ladders was associated not only with spawning migrations but also reflected shifts in local fish distribution in response to flow variability in the main channel.     

Mismatch between fishway operation and timing of fish movements: a risk for cascading effects in partial migration systems

Habitat fragmentation is a growing problem worldwide. Particularly in river systems, numerous dams and weirs hamper the movement of a wide variety of species. With the aim to preserve connectivity for fish, many barriers in river systems are equipped with fishways (also called fish passages or fish ladders). However, few fishways provide full connectivity. Here we hypothesized that restricted seasonal opening times of fishways can importantly reduce their effectiveness by interfering with the timing of fish migration, for both spring‐ and autumn‐spawning species. We empirically tested our hypothesis, and discuss the possible eco‐evolutionary consequences of affected migration timing. We analyzed movements of two salmonid fishes, spring‐spawning European grayling (Thymallus thymallus) and autumn‐spawning brown trout (Salmo trutta), in Norway's two largest river systems. We compared their timing of upstream passage through four fishways collected over 28 years with the timing of fish movements in unfragmented river sections as monitored by radiotelemetry. Confirming our hypothesis, late opening of fishways delayed the migration of European grayling in spring, and early closure of fishways blocked migration for brown trout on their way to spawning locations during late autumn. We show in a theoretical framework how restricted opening times of fishways can induce shifts from migratory to resident behavior in potamodromous partial migration systems, and propose that this can induce density‐dependent effects among fish accumulating in lower regions of rivers. Hence, fragmentation may not only directly affect the migratory individuals in the population, but may also have effects that cascade downstream and alter circumstances for resident fish. Fishway functionality is inadequate if there is a mismatch between natural fish movements and fishway opening times in the same river system, with ecological and possibly evolutionary consequences for fish populations.     

Behaviour and Locomotor Activity of a Migratory Catostomid during Fishway Passage

Fishways have been developed to restore longitudinal connectivity in rivers. Despite their potential for aiding fish passage, fishways may represent a source of significant energetic expenditure for fish as they are highly turbulent environments. Nonetheless, our understanding of the physiological mechanisms underpinning fishway passage of fish is still limited. We examined swimming behaviour and activity of silver redhorse (Moxostoma anisurum) during its upriver spawning migration in a vertical slot fishway. We used an accelerometer-derived instantaneous activity metric (overall dynamic body acceleration) to estimate location-specific swimming activity. Silver redhorse demonstrated progressive increases in activity during upstream fishway passage. Moreover, location-specific passage duration decreased with an increasing number of passage attempts. Turning basins and the most upstream basin were found to delay fish passage. No relationship was found between basin-specific passage duration and activity and the respective values from previous basins. The results demonstrate that successful fishway passage requires periods of high activity. The resultant energetic expenditure may affect fitness, foraging behaviour and increase susceptibility to predation, compromising population sustainability. This study highlights the need to understand the physiological mechanisms underpinning fishway passage to improve future designs and interpretation of biological evaluations.     

The influence of freshwater flows on two estuarine resident fish species show differential sensitivity to the impacts of drought,flood and climate change

Estuaries are particularly susceptible to climate change and drought resulting in atypical changes to freshwater flows. How such changes in flow impact on the ecology of estuarine fishes may depend on how a species moves in response to changing flow conditions. Acoustic telemetry was used to interpret fine-scale movements of two co-inhabiting estuarine fish species, black bream, Acanthopagrus butcheri and estuary perch, Macquaria colonorum in relation to freshwater flows, season and moon phase. We found black bream to be highly mobile, regularly travelling the length of the estuary and into the neighbouring estuaries. In contrast, estuary perch had particular home ranges and made occasional, upstream or downstream movements. Possibly influenced by freshwater flows, estuary perch moved at greater rates in the Tambo compared to fish in the Mitchell. Black bream resided in the upper estuary during winter and spring and the lower estuary during summer and autumn, whereas estuary perch remained in the upper estuary throughout the year, with occasional downstream movements in winter and spring. This study revealed 1) significantly large increases in freshwater flows result in mass downstream movements in both species, 2) fish moved upstream during full moons and 3) there are contrasting spatio-temporal patterns in movement between species. The results from this study highlight that estuarine fishes are likely to show differential sensitivity to the impacts of drought and climate change and illustrate how acoustic telemetry methods can be used to determine the environmental needs of fishes and help efforts to conserve and manage estuaries worldwide.     

Anthropogenic changes in the freshwater fish fauna of Italy, with reference to the central region and Barbus graellsii, a newly established alien species of Iberian origin

In a survey of the west-central Italian rivers Ombrone, Fiora, Albegna and Bruna, among established exotic species, the Iberian barbel Barbus graellsti was recorded in Italian fresh waters for the first time. Morphological identification was supported by comparison of cytochrome b sequences with those from related barbel species. Other exotics of particular note were Barbus barbus, Pseudorasbora parva and Leuciscus cephalus , together with the Padano-Venetian Chondrostoma genei and Padogobius bonelli. Native species still present included Leuciscus lucumonis, Telestes muticellus, Rutilus rubilio and Padogobius nigricans , but were now more restricted to upper reaches and smaller watercourses. The deleterious effect of alien species on native forms is discussed with particular reference to probable competition between C. genei and L. lucumonis , and between the two gobies. The checklist of species introduced to the fresh waters of Italy is now updated to 34. For the Italian freshwater fish fauna in general, the conservation status of three native species ( Acipenser naccari, Salmo marmoratus and Knipowitschia punctatissima ) has been improved but five species are believed to be at risk ( Salmo carpio, L. lucumonis, Scardinius scardafa, Gobio benacensis and P. nigricans ) and four anadromous species ( Petromyzon marinus, Lampetra fluviatilis, Acipenser sturio and Huso huso ) no longer breed in Italian fresh waters. The processes of change in the composition of the Italian freshwater fish fauna as a whole may be summarized as successively 'padanization', 'danubization' and now 'globalization'.     

Comparing fish assemblages and trophic ecology of permanent and intermittent reaches in a Mediterranean stream

Mediterranean streams are characterised by seasonal droughts, the frequency and intensity of which vary spatially and are expected to increase with global change. We studied the potential effects of drought and climate change on the fish assemblage and its trophic ecology in a Mediterranean stream by comparing an intermittent tributary with two more permanent neighbouring reaches. Although the three sites were dominated by the same two fish species, Mediterranean barbel (Barbus meridionalis) and chub (Squalius laietanus), the intermittent tributary had a lower overall fish density and fewer eel (Anguilla anguilla). The intermittent tributary had macroinvertebrates with lower density, smaller taxa and higher diversity. Fish in the intermittent tributary had significantly lower biomasses in their gut contents (adjusted for fish length) and more negative electivities than those in the permanent reaches, as well as significantly lower taxonomic diversity. These results indicate that there was reduced resource availability in the intermittent tributary, which resulted in significantly lower condition and gonadal weight (adjusted for length) of barbel and chub. The data obtained in this Mediterranean stream support the observation that reduced water flow may affect fish at both individual and assemblage levels.     

Fish migration through a fish passage associated with water velocities at the Changzhou fishway (Pearl River,China)

Hydraulics play an essential role in successful fish passage through fishways, yet little is known about the response of fish species to specific hydraulic characteristics. This study aims to determine the response of fish presence to water velocity that results from the flow regulation in the Changzhou Fishway (CFW). Water velocity meters and fish traps were used in the study to monitor water velocities and the presence of fish species at flood control levels as well as at normal pool levels. Water velocities in the CFW have a varied significantly as result of flow regulation, whereby water velocities at flood control levels are significantly higher than at normal pool levels (P = 0.014). A total of 3558 fish representing 28 species collected in the CFW were divided into two groups by cluster analysis. This type of divergence in species is strongly associated with the two controlled water levels in the fishway, wherein pelagic species predominate at normal pool levels, and demersal species predominate at flood control levels. This study suggests that the variations in water velocities trigger the shifts in species compositions that in the use of CFW.