Blame the communists...
I just learned something today that I never knew before!!! I wrote a few days ago about the custom of eating carp on Christmas Eve. Other fish is eaten too--sometimes trout, and herring is very popular. But carp is not a long-standing Polish tradition.
During the lean communist years, carp was simply the only fish available. People couldn't get anything else, so they had carp, because fish was the traditional meal.
But here is what is kind of funny--not all Polish people know this! The woman who told me (in her 50's) didn't know it until recently. So here we have a glorious tradition--big stores and outdoor markets offering live carp, and people lining up to buy it...just because their parents and grandparents had to make do with this not-very-tasty fish.
There's a message here somewhere, and if it weren't so late on Sunday night, I'd try to figure it out.