As a bit of historical trivia, muskrat is approved for consumption during Lent in the Archdiocese of Detroit.
It dates back to the days of the Jesuit missionaries to the local tribes. Their word for ‘fish’ also included aquatic mammals.
In a concession to aid in conversions, the Jesuits requested a dispensation from the Bishop in Montreal.
The dispensation was renewed as particular law when Detroit became it’s own dicoese and still remains.
Up through the turn of the century, it was somewhat of a tradition in Detroit to have muskrat during Lent. I know of one butcher shop that still caries it during Lent, but the custom is all but disappeared.