After a few days of trying to figure out what the Otter was feeding on and finally I have found an answer. At first I think it may have been Fish, Freshwater Mussels, Water Birds but a walk the other evening revealed what I think the Otter was feeding on. While taking an sunset walk we spotted movement in the water as the light began to fade so I used my torch and the movement maker was revealed which was toads. As the canal has warmed up in the warm weather it has set off the Toads breeding season when they leave the safety of the reed beds in the area to begin there short breeding season.
On my way back I heard a crunching in the reeds and a Moorhen alarm calling it turned out there was a pair of Foxes also having a snack on either Frogs' Toads or eggs in a birds nest.