Thats the footprints:

But be careful, the are not easy to identify!
      front                   rear

           hearing: Example soundfile for download
 

Scats:

The fishotter is quite helpful in this respect.
İt preferes "standing out" places, like single bolders or or even big branches of tree.

Colours can be lightly greyish to green or black.
The smell is very caracteristic, but not unpleasant. Once you had it in your nose, you wont forget it! That is why the animal leaves the scats, they should be found! Not by humans of course, but by their neighbour otters.