I have a friend who works on similar programs in the UK. They are rebuilding marshland near Cambridge and building grates/sluices to let eels swim through and back to their spawning points. It's cool stuff!

Edit: Eels and other similar fish often have a mild electrical sense, it's like echolation but zaps instead of yelling. Some can use their zaps like a taser but most are just using it to know where they are: https://dwazoo.com/animal/electric-eel/