After having a few incidents with mouse-filled boats, the best option we've found is traps everywhere.
We tried poison but it is really a LAST RESORT. Anything eating the mice will also be poisoned (owls, snakes) which in turn lets the mouse population explode.
About a decade ago, we thought we had a snake problem at the cabin. After killing a couple dozen snakes we had an explosion in the mouse population (mice in the coffee pot, drowned in the toilet, etc). Just like removing wolves and watching the deer population explode - mother nature keeps everything in balance unless we f*** with it.