Traps are the only way to get rid of them - I have never seen an otter near the pond. They are careful.... You can't shoot animal that you don't see
Unless you have traps and nightvision snipers 24-7 the best way to keep otters out is an electric fence, they don't appreciate 8000 volts. The only drawback is during winter when heavy snow covers the fence. There's always a chance a Heron could airdrop an otter into the pond.
The only drawback is during winter when heavy snow covers the fence. There's always a chance a Heron could airdrop an otter into the pond. 
