The River Scheldt is an international river and runs from France through Belgium to discharge in the North Sea in the Netherlands, spanning ca. 400 km. It is one of last larger river basins in Europe with a well-developed estuary and tidal influence up to 160 km inland. Even more, since 2004 artificial wetlands are being developed (i.e. the Sigma Plan) to stimulate biodiversity and flood protection. Due to its free connectivity with the sea, it is an important migration route for diadromous fish species such as the European eel, river lamprey and twaite shad. Obviously, the system houses numerous obligate freshwater fish species as well such as bream, roach, pike, zander, perch, gudgeon, wels catfish etc and reintroduction programs for example brown trout are in the running.

Water quality has improved substantially since the last 15 years due to the installation of water treatment plants. Also the construction and optimization of fish ways are planned the coming 5 years. Nonetheless, pollution spill calamities still occur and all to frequent. The river just recovered from a major spill 8 years ago or another natural disaster struck again on the 9^th of April 2020: 100,000 m³ liter of sugar beet residues from the sugar company Tereos ran into the River Scheldt, leading to a total oxygen depletion and hence natural disaster for aquatic life. Although the abundance of dead fish is still being quantified, it is suspected that 99.5% of the fish died in the first 87 km downstream of the spill. As the severity of the spill became clear in Belgium, authorities cooperated at an unseen level to reduce its impact on the environment by, for instance, placing aerating devices and activating water treatments plants. Nonetheless, for the 87 km of Scheldt River, all conservation efforts to stimulate aquatic biodiversity and life have been brought down to zero.

Hence, as long as such large pollution spill calamities occur, aquatic habitat and life depending on clean water are unlikely to improve. Actually, among the victims was a female Allis shad full of eggs; a first in a 100 years and probably gone again. Also many large eels (> 80 cm) were drifting motionless on the surface, individuals likely over 10 years old and never to contribute to the next generation.

Water is a vital life source and a precious resource, which is becoming more scarce in some parts of the world due to climate change. It is therefore of prime importance to create awareness about the incredible life blow the water surface, halt aquatic pollution and improve biodiversity in our rivers.

---

---

---

Dr. Pieterjan Verhelst
Marine Biology research group
Ghent University
Belgium