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Producción Científica, Water temperature and flow velocity directly affect the fish swimming capacity, and thus, both variables influence the fish passage through river barriers. Nonetheless, their effects are usually disregarded in fishway engineering and management. This study aims to evaluate the volitional swimming capacity of the northern straight-mouth nase (Pseudochondrostoma duriense), considering the possible effects of water temperature, flow velocity and body size. For this, the maximum distance, swim speed and fatigue time (FT) were studied in an outdoor open-channel flume in the Duero River (Burgos, Spain) against three nominal velocities (1.5, 2.5 and 3 m s−1) and temperatures (5.5, 13.5 and 18.5°C), also including the changes between swimming modes (prolonged and sprint). Results showed that a nase of 20.8 cm mean fork length can develop a median swim speed that exceeds 20.7 BL s−1 (4.31 m s−1) during a median time of 3.4 s in sprint mode, or 12.2 BL s−1 (2.55 m s−1) for 23.7 s in prolonged mode under the warmest scenario. During prolonged swimming mode, fish were able to reach further distances in warmer water conditions for all situations, due to a greater swimming speed and FT, whereas during sprint mode, warmer conditions increased the swim speed maintaining the FT. In conclusion, the studied temperature range and flow velocity range influence fish swimming performance, endurance and distance travelled, although with some differences depending on the swimming mode. The provided information goes a step forward in the definition of real fish swimming capacities, and in turn, will contribute to establish clear passage criteria for thermo-velocity barriers, allowing the calculation of the proportion of fish able to pass a barrier under different working scenarios, as well designing of the optimized solutions to improve the fish passage through river barriers., Junta de Castilla y León (proyecto VA299B11-2), Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 101032024

This study aims to describe pre-reproductive movements of Luciobarbus bocagei and Pseudochondrostoma duriense in a regulated canyon-stretch of the Tormes River (Spain), with high environmental variability, semipermeable barriers, and fishway retrofitting actions. The main objectives were to identify peak migration dates and environmental drivers, test ensemble-learning techniques to model fish migration and propose adaptive management measures. To achieve this, fish movements were 5-year monitored in a stepped fishway and Survival Analysis and Random Forest techniques were used for data analysis and modelling. Results showed that migration occurred in May–July, a wider period than the one previously reported in the literature. Movements were triggered by the increase in water temperature and photoperiod, and were strongly affected by the hydraulic river scenario (water levels and discharge) at the semipermeable barriers. Random Forest was able to include the effect of each barrier and predict accurately timing and number of migrants, classifying and ranking the importance of variables. Moreover, developed models allowed to assess fishway retrofitting actions and to predict positive effects in fish number under new, scheduled and variable environmental flow scenarios. Long-term monitoring together with ensemble-learning methods can allow the definition of cost-effective adaptive management strategies to ensure endemic fish conservation.

espanolEl grado de alteracion antropogenica en los ecosistemas fluviales es elevado, debido, fundamentalmente, a la creacion de barreras transversales (presas, azudes, estaciones de aforo, canos de drenaje, etc.), que alteran su conectividad longitudinal, causando, entre otros impactos, la fragmentacion del habitat. Esta problematica afecta a los peces migradores, pues puede suponer un bloqueo o retraso en sus movimientos, reduciendo sus habitats, amenazando la viabilidad y abundancia de sus poblaciones, llegando incluso a su extincion. La capacidad de nado de los peces (velocidad de nado, tiempo de fatiga y distancia recorrida) es uno de los factores que determina su supervivencia. Un sistema que permite establecerla en condiciones naturales son los canales de nado voluntario. En el canal de nado de Vadocondes (Burgos) se ha determinado la capacidad de nado y como influyen en ella factores ambientales y biometricos, de dos de las principales especies de ciprinidos potamodromos de la Peninsula Iberica (barbo iberico –Luciobarbus bocagei– y boga del Duero –Pseudochondrostoma duriense–, con el objetivo de poder desarrollar unas directrices tecnicas y cientificas adecuadas, que garanticen un diseno optimo y eficaz de los pasos para peces, que repercuta positivamente en la conservacion de sus poblaciones. EnglishThe anthropogenic alteration in fluvial ecosystems is high, mainly due to the creation of transverse barriers (dams, weirs, gauging stations, drainage pipes, etc.), which modify their longitudinal connectivity, causing, among other impacts, the fragmentation of the habitat. This problem affects the migrating fish, because it can suppose a blockade or delay in their movements, reducing their habitats, threatening the viability and abundance of their populations, even reaching their extinction. The swimming capacity of the fish (swimming speed, fatigue time and distance traveled) is one of the factors that determine their survival. A system that allows to establish it, in natural conditions, are the voluntary open channel flume. In the flume of Vadocondes (Burgos) the swimming capacity has been determined, and how environmental and biometric factors influence in the swimming capacity, of two of the main species of cyprinids potamodromous of the Iberian Peninsula (Iberian barbel –Luciobarbus bocagei– and northern straight-mouth nase –Pseudochondrostoma duriense–, with the aim of being able to develop adequate technical and scientific guidelines, which guarantee an optimal and effective design of the fishways, which has a positive impact on the conservation of their populations.

espanolLa construccion de obras transversales en los cursos de agua causa, entre otros aspectos, un gran impacto en la continuidad longitudinal de los ecosistemas fluviales. Para paliarlo y permitir el libre desplazamiento de la fauna (especialmente peces) es frecuente la construccion de pasos piscicolas. Sin embargo, a pesar de haberse construido en gran numero durante las ultimas decadas, son pocos los casos en los que se ha evaluado su funcionalidad. Asi, la Confederacion Hidrografica del Duero, el Grupo de Ecohidraulica Aplicada (GEA) de la Universidad de Valladolid e Itagra.ct han desarrollado una nueva metodologia de evaluacion del funcionamiento de pasos para peces de estanques sucesivos (Metodologia AEPS) que ha sido aplicada en mas de 50 de estas estructuras. La metodologia analiza la idoneidad de los pasos piscicolas para una serie de especies objetivo atendiendo a multiples parametros de diseno y factores eco-hidraulicos, pudiendo ser utilizada con pequenos ajustes en diversas areas y para diferentes especies. Por otro lado, su aplicacion ha permitido conocer la situacion actual de los pasos para peces en la cuenca del rio Duero, identificar sus problemas y como solucionarlos. EnglishCross-sectional barriers in rivers cause, among others, an impact on the longitudinal connectivity of river ecosystems. It is frequent to build fish passes to palliate this impact and to enable free movements of the fauna (especially fish). However, even though they have been massively built during the last decades, their functionality has been scarcely assessed. Duero River Authority (Confederacion Hidrografica del Duero), Ecohydraulic Applied Group (GEA) of the University of Valladolid and Itagra.ct have developed a new assessment methodology of the functionality of stepped fish passes (Methodology AEPS). This methodology has been tested in 50 of these structures. It analyzes the suitability of the fish passes for target species attending to design parameters and eco-hydraulic aspects. It can be used in different areas and for different species with minor modifications. Its implementation has allowed to know the current situation of the fish passes in the Duero River basin, identifying their problems and how to solve them.

Knowing the relationship between size, morphological traits and swimming performance of fish is essential to understand the swimming capacity to successfully surpass these obstacles and the selective pressure that barriers in rivers and streams could exert on fish. Northern straight-mouth nase, an endemic potamodromous cyprinid fish species from the Northwest of the Iberian Peninsula, was selected to carry out volitionally swimming performance experiments in an open channel against three different flow velocities, using telemetry and video cameras. The use of thin-plate spline, on 10 landmarks, evidenced unknown patterns linked to velocity barriers. At lower flow velocity, size is the main factor explaining the swimming performance; thus, large individuals swim up more efficiently. In contrast, at high flow velocities, shape becomes the essential explanatory variable; thereby, streamlined body shapes with a higher relative position of the tail and a narrower caudal peduncle are more efficient. The obtained results show the existence of a relationship between fish morphology and swimming performance, with potential consequences due to selection pressures associated with velocity barriers and their implications on behavioural and dispersal processes. To sum up, velocity barriers could exert a selection pressure on nase populations, so the fishway design and removal should be (re)considered.

Many fish passes have been built across the world in recent years. This study analyses the performance of a modified type of pool and weir fishway with two access branches, using passive integrated transponder telemetry. A circum‐Mediterranean barbel, Luciobarbus bocagei (Steindachner, 1864), was chosen as the target species. Both hydraulic values (flow and volumetric energy dissipation) and biological parameters (attraction, entrance and passage success) were measured in the fishway, these being related to the environmental variables affecting upstream fish movement. Flow discharge, water temperature and atmospheric pressure were important for fish entering the fishway. There was no preference between path routes, even though the main discharge was concentrated in the turbine channel. This type of fishway design could be an alternative for the conservation of fish populations where multiple fish approach options are possible.

El hombre en el desarrollo de sus actividades ha utilizado los cursos fluviales como uno de sus principales recursos. En este proceso ha alterado su composición, estructura y funcionamiento, y en consecuencia alterado sus regímenes hidrológicos. En este sentido, una de las principales alteraciones es la existencia de obstáculos transversales que restringen o imposibilitan el movimiento de la fauna piscícola a lo largo de los ríos. Estudiar la capacidad de natación de las principales especies de la ictiofauna de la Península Ibérica es fundamental para poder realizar diseños óptimos y más eficaces de estos obstáculos, así como de las alternativas a su paso, Departamento de Ingeniería Agrícola y Forestal, Doctorado en Conservación y Uso Sostenible de Sistemas Forestales

Fishways are used worldwide to restore fish migration routes. However, there are few standardized metrics that allow the comparison of their performance in a consistence manner. This paper aims to assess fishway internal passage using two standardized metrics: passage success and transit time. Data from selected 20 field stepped fishways evaluation were gathered from a systematic review and own field experiments, considering potamodromous species as target fish. The influence of main biological and hydraulic parameters on these metrics was analyzed and modeled by logistic regression and survival analysis techniques. Passage success and transit time described reliably fishway performance. Both metrics were significantly influenced by fishway type, volumetric power dissipation, height drop between pools, slope, obstacle height, pool depth, species and fork length in fishway passage. This work may serve as a guide for all engineers and managers working in fishway assessment, design and management to assess and compare other fishways, select proper design parameters and open the discussion and future research on these topics.

Restoring the longitudinal connectivity of rivers is one of the main objectives of environmental European directives and policies. Fish passes or fishways are one of the most common actions for its restoration. Despite the great number of fish passes constructed during the last two decades to comply with these policies, few of them have been assessed and their suitability for fish movements is unknown. There are different options to assess fish passes, but time and economic costs frequently limit their application. Coarse fishway assessment methods (CFAMs) are an easy, fast and economic alternative for this purpose. This study aims to display the potential of CFAMs to evaluate a large number of fishways, to show the actual status of fishways in an Iberian representative river basin, and to diagnose their suitability and problems. For this, the Spanish Duero River Authority promoted the assessment of 64 stepped fishways in the Duero River basin (Spain) using the AEPS methodology. The results were analyzed considering the four stages that a fish must overcome in a fishway (attraction, entry, passage and exit), the fishway type and the construction period. Among others, results show that 50% of the assessed fishways allow the free movement of fish. However, this percentage could have been greater applying an adequate monitoring program for the fishway design and construction. Furthermore, the diagnosis by stages of the AEPS methodology allowed to identify the attraction and passage as the most problematic stages and also helped to define specific retrofitting solutions for each fishway. The study concludes that the application of CFAM during fishway design, construction and first operation stages can increase their effectiveness and, thus, the number of fish passes that contribute to the restoration of the longitudinal connectivity of rivers.

This paper presents sprinting data from Iberian barbel (Luciobarbus bocagei) and northern straight-mouth nase (Pseudochondrostoma duriense), volitionally swimming against high velocity flows (1.5, 2.5 and 3 m s−1) in an open channel flume. Swimming endurance and speed greatly exceeded previously published observations with both species attaining swim speeds >20 body lengths s−1. Flow velocity was the primary variable limiting the distance both species were able to traverse. Barbel swam greater distances than nase at higher flow velocities, with longer individuals attaining greater distances than smaller ones. The results challenge established fish passage guidelines, suggesting that in some cases these species are capable of passing much higher velocities than was previously believed.

espanolEl presente trabajo analiza la capacidad voluntaria de nado del barbo iberico (Luciobarbus bocagei Steindachner, 1864) en un canal abierto durante su epoca de migracion, relacionandola con factores ambientales y biometricos. La temperatura del agua, la velocidad de flujo y la longitud del pez fueron los factores de mayor importancia que condicionaron la velocidad de nado de los barbos y su tiempo de fatiga. Dentro del rango de valores estudiado, el barbo iberico pudo mantener velocidades de nado en sprint (> 15 BL/s) durante 3-10 s, y de 17-117 s en el modo de natacion prolongada (7-15 BL/s). Los resultados aportados pueden ser empleados como una herramienta util para la gestion de sus poblaciones, principalmente para el diseno de pasos para peces. EnglishThis paper analyzes the volitional swimming capacity of the Iberian barbel (Luciobarbus bocagei Steindachner, 1864) in an open flume during its migration period, in relation to environmental and biometric factors. Water temperature, flow velocity and fish length were the most important factors which affected the swimming speed of barbels and their fatigue time. Within the range of values studied, the Iberian barbel was able to maintain sprint swim speeds (> 15 BL/s) for 3-10 s, and 17-117 s in prolonged swim mode (7-15 BL/s). The results can be used as a tool for the management of barbel populations, mainly in the design of fishways

When engineers and ecologists face a fishway design, many issues need to be considered, the type of fishway being the first and foremost. It is an especially complex issue in areas with species whose migratory and swimming behavior are as yet poorly known as Mediterranean barbels. The present study focuses on the fish passage of two of the most common types of technical fishways: Vertical Slot (VS), and Submerged Notch with Bottom Orifice (SNBO). Both types were studied and compared in terms of ascent ability (as the success rate and transit time) and motivation (as the proportion of attempts and attempt rate), with Iberian barbel (Luciobarbus bocagei) as the target species. Ascent ability in VS and SNBO were similar. More than 90% of fish ascended the fishways successfully and the median transit time to ascend a total water height of 2.25 m was less than 23 min. Fish length had an effect on ascent time, with the biggest ones being faster. Motivation was greater for VS, although not seeming to have a relevant influence in the passage. These results support the use of VS and SNBO in areas with Iberian barbel and provide new data of fishways performance helping ecologists and engineers with their decision making, mainly in Mediterranean areas with similar habitats and species.

Sprinting behavior of free-ranging fish has long been thought to exceed that of captive fish. Here we present data from wild-caught brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta), volitionally entering and sprinting against high-velocity flows in an open-channel flume. Performance of the two species was nearly identical, with the species attaining absolute speeds > 25 body lengths·s−1. These speeds far exceed previously published observations for any salmonid species and contribute to the mounting evidence that commonly accepted estimates of swimming performance are low. Brook trout demonstrated two distinct modes in the relationship between swim speed and fatigue time, similar to the shift from prolonged to sprint mode described by other authors, but in this case occurring at speeds > 19 body lengths·s−1. This is the first demonstration of multiple modes of sprint swimming at such high swim speeds. Neither species optimized for distance maximization, however, indicating that physiological limits alone are poor predictors of swimming performance. By combining distributions of volitional swim speeds with endurance, we were able to account for >80% of the variation in distance traversed by both species.