Maine’s lakes enjoy some of the best water quality in the country, for the simple reason that they have some of the coldest water in the country. Lake health, including the health of the fish population, is directly correlated to water temperature, which, in turn, is directly correlated to the length of time that a lake maintains its ice covering. Global warming is shortening the time each year when Maine lakes are ice covered, and this may eventually result in a decline in water quality and adverse effects for lake fish populations.
Please see this excellent article on the subject from the Portland Press-Herald: Diminishing Ice Cover on Maine's Lakes Could Impact Fish Populations.
As for West Harbor Pond, Leslie Volpe has been monitoring ice-in/ice-out since 2010, and the data that she has collected are compiled in the table below. You will note that in 2021 the Pond was ice covered for only 49 days, the shortest period in Leslie’s data. She also points out that there was an earlier almost-ice-in December 2022, but it was precarious due to the warming weather and quickly disappeared with the rain over Christmas.