Abstract
A river is an ecosystem where fish fauna represents an important structural element. To re-establish connectivity, it is imperative to allow movement between functional habitats. Due to the hydromorphological complexity of large anthropized rivers and the lack of study techniques that can be used in such environments, relevant data with regard to fish ecology are scarce. On the River Meuse, Belgium, at a point 323 km upstream from the North Sea, the Lixhe hydroelectric dam is equipped with two fishways. Both were continuously monitored using capture traps for 20 consecutive years (from 1999 to 2018), representing 4151 monitoring events. The objectives of the present study were to describe the overall abundance and movement indicators of mainly holobiotic potamodromous fish species and to analyse their temporal evolution. We captured 388,631 individuals (n = 35 fish species) during the 20 years of fishway monitoring; 22.7% were adults (>75% of which were cyprinids), and 83.3% juveniles (>90% cyprinids). From 1999 to 2018, the results showed a drastic reduction in yearly captures for some native species as well as the apparent emergence of non-native (e.g., Silurus glanis) and reintroduced species (e.g., Salmo salar). The annual capture periodicities associated with environmental factors were clearly defined and were mostly related to the spring spawning migration of the adult stage. This long-term monitoring demonstrated how the fishways are used by the whole fish community and allowed a better understanding of their movement ecology in a large lowland anthropized river. The appearance of non-native species and the drastic decline in abundance of some common and widespread European fish should prompt river managers to adopt conservation measures.
Highlights
In an ecosystem where fish fauna represents an important functional element, it is imperative to re-establish connectivity to allow each species to complete its life cycle [5,6,7], because these barriers fragment previously natural rivers and can preclude movement between functional habitats [8,9]
Over the 20 years of monitoring, we observed that fishways in a large anthropized river were used by diverse fish species across a wide variety of stages and size ranges
The increase in size of eel and bream were significantly associated with decreased numbers of annual captures
Summary
Rivers are fragmented by many obstacles for the purposes of hydropower, navigation, flow control, or water supply [1]. River fragmentation by dams causes physicochemical and hydromorphological modifications of upstream and downstream habitats, hydropeaking, alterations to the river’s natural flow, and obstruction to sediment and biological organisms such as fish and invertebrates [2,3,4]. In an ecosystem where fish fauna represents an important functional element, it is imperative to re-establish connectivity to allow each species to complete its life cycle [5,6,7], because these barriers fragment previously natural rivers and can preclude movement between functional habitats [8,9].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
