Problem is that eel numbers are down, probably down to various causes, pollution being one, and eels were apparently otters favourite food. Back in the 1980's the Wensum in summer you could see 100's on the bottom, then they started being caught with sores around the area of Hellesdon, just below the chemical factory outlet.
The Broads, lakes and rivers, it was almost impossible to use maggots as a hookbait if you fished the bottom.
On the Gipping I used to stand on the bridge to Sugar Beet pits and feed maggots to the silvers, what they missed, eels would pick up of the bottom, you could see them.
However this lack of eels is not restricted to East Anglia, it's nationwide.
Behind Barham Pits there was a pair of otters, the river was full of big chub, gudgeon, perch, roach and pike. Then an otter explosion saw more appear in the valley, so where 4 or 5 were between Ipswich and Stowmarket, 18miles, (by road) there were now at least 15 otters, and 4 were on Barham, and another 4 on Bosmere, munching everything sizeable.
As I mentioned though, my syndicate is not fenced, yet has little trouble. Coots go missing in winter and we lose occasional pike, not many. I think that at night otters stalk the rushes coot hunting as they will suddenly chirp and scatter. That is also pike territory!