Levelling Up on a European Eel Extinction?

The Levels is a flat landscape in north and central Somerset. These Levels are essentially 69,000 hectares of wetland and coastal plain. This area has, since ancient times, been drained and farmed by humans. The Levels have also been a regular breeding area for the European eel, after making its long migration from the open sea. It seems, however, that eels (once so prolific, they were used as currency in the area) are completely absent from the Level's drains (https://www.theguardian.com/environment/2023/aug/23/no-evidence-eel-dna-somerset-levels-analysis-water-shows). The Sustainable Eel Group and the Somerset Eel Recovery Project paid for DNA studies of filtered water samples from the Somerset Levels drains. They were shocked to find there were no traces of eel DNA. Perhaps, barriers erected in the wetland, to keep water back from farmland and homes, have played a role? If so, eel 'ladders' facilitating fish migration over barriers, may prove helpful.