I'll second Dave's comment; since I don't enjoy dispatching anything without cause - but in the case of otters in fishing ponds, there's ample cause.
I've been helping a nearby landowner thin his beaver population since they were burrowing into the pond's levee at multiple sites. The 330 Conibears did the deed on 6 beavers - and then nothing else for 4 weeks. Out of nowhere, I caught a lone adult male otter in a beaver-set. One week later, I caught four adult female otters in one night - all four were taken from around the island in this photo.
I only set my Conibears underwater to avoid non-targeted critters such as coons, but any beaver-targeted set is subject to also nabbing an otter.
The pond in question is only an acre, so five otters could sure do some damage to the fishery if left to satisfy their penchant for fish-flesh.
330 Conibears are the way to go IMO, assuming you don't want to attempt relocating your fish-thieves to someone else's property.
