Beginning on February 2, 2018, I had the privilege of watching a family group of 3 otters fishing, swimming, and playing on the ice at a small mill pond in Sharon, Massachusetts. Trowel Shop Pond is right off of route 27 on North Main Street. As of February 10, 2018, the ice broke up and the otters have appeared to move on.
I watched the otters catch many fish, averaging about one fish every 5 minutes while I was on the shore of the pond. Most of the fish were sunfish, primarily bluegills and pumpkinseeds. I also saw the otters catch crappie, perch, and largemouth bass.
Otters are secretive, but there are characteristic patterns when they are using a pond that has frozen over.
While I watched the otters over 7 days, it was clear that they were maintaining a series of holes in the ice, even on days below zero. At the ice holes, there was a characteristic that indicated otters were present. If you look at the photo below and the one on the left, you will notice that the ice refreezes fresh and clear every time an otter comes out on the ice to eat a fish. Even when otters are not visible, you can see these characteristic patterns of frozen ice.