Concrete walls, tidal flaps, sluice gates and weirs are just some of the many obstacles these tiny creatures come up against as they try to swim up rivers to reach the inland waterways where they can grow to adulthood. Consequently, the number of eels in Britain's waterways has slumped.
Now a review of British rivers will identify structures that can be pulled down, or sites that are suitable for eel-friendly bypasses. In some cases, a pipelined with grippy mesh is all that is needed for the eels to get past a man-made obstacle.