Desarrollo y aplicación de una nueva metodología para la evaluación de pasos para peces de estanques sucesivos

Resumo

Watercourses around the world are fragmented by the presence of human-made transversal obstacles. To restore their longitudinal connectivity, structures named fish passes are massively constructed. Despite their large number, their performance is studied just in some cases, with very different results. Among the existing alternatives to evaluate their performance are the hydraulic assessment methods, characterized by their easy, fast and economical application. The main objectives of this thesis are to develop, test and apply a new hydraulic method to evaluate reliably the most common typology of fish passes, the stepped or pool-type fishways, in order to know the performance of some of these structures located in the Iberian Peninsula. To achieve these objectives, different actions were performed. An assessment methodology was developed based on bibliographic information and field experiences. It analyses the aspects of the fishways that influence the ascent of three Iberian fish species. The methodology was applied in different river basins to study the effectiveness of various fish passes. The results of its application were analyzed attending to the typology of the fishways, the different stages to overcome by fishes into a fish pass (attraction, entry, passage and exit) and the time when they were constructed. The methodology assesses many fish passes in detail and objectively based on hydraulic and biological information, allowing it to retains the advantages and reduce the disadvantages of the hydraulic assessment methods. The results of its application reveal that 55 % of the evaluated fishways are adequate for fish movements, being most of them recently constructed. The observed deficiencies in the fish passes are due to their design, construction and operation, demonstrating the need to evaluate these structures during the three phases to enhance their final performance. This thesis provides a practical tool for understanding the performance of stepped fishways, identifying their problems and helping to solve them to improve the current and future fish passes.