> it was ok to eat barnacle geese at lent.

I think that was just a way to ethically cheat the fast...In southern Germany they got around it by wrapping the meat in a dumpling (Maultaschen), so that god wouldn't notice: "The Swabian German nickname for the dish, Herrgottsbescheißerle, means "small God-cheaters""

https://en.wikipedia.org/wiki/Maultasche#History

EDIT: just remembered another similar cheat, where beavers were defined as fish, allowed to be eaten at lent.