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.
<p>Las escalas de peces de hendidura vertical son estructuras hidráulicas diseñadas para permitir la migración de las especies piscícolas a través de obstáculos en ríos. El diseño adecuado de estos dispositivos depende de la interacción entre variables hidráulicas y biológicas, dado que las propiedades hidrodinámicas de la escala deben ajustarse a los requisitos de las especies objetivo. En este artículo se presenta una aplicación informática que analiza la eficiencia de un modelo de escala de acuerdo con criterios biológicos. El modelo propuesto aplica restricciones referidas a la capacidad de natación de los peces, a sus necesidades de calado y a sus requisitos en relación con la energía disipada en forma de turbulencias. Permite así comparar diseños de forma objetiva y determinar cuál será previsiblemente más eficiente. Con esta herramienta se busca facilitar a los técnicos involucrados en el diseño de escalas de peces de hendidura vertical la aplicación sistemática de criterios hidrobiológicos, que incorporen además los resultados de las investigaciones más recientes en este ámbito.</p>
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