I have found if you are close to a river you will have otters, and in the long term, cannot win. After the big loss we have taken in the past seven months due to otters, we are reluctant to spend much more on the ponds. A place far from a permanent stream is better to build ponds in. The otters will eventually eat every fish in the pond that is bigger than 4 or 5 inches, leaving only fingerlings. Discouraged.