We have a 20ha dam that is very regularly stocked with Rainbows.

Unfortunately, we also have a healthy population of Cape Clawless Otters (About 8). Does anyone have any evidence of otters' impact on trout populations? We also have herd of Largemouth Bass as a food source for the otters.

Otters are a protected species, so a .22 with a silencer is not really an option, how else can I get rid of these, if it is actually necessary?