they're being served as appetizers.
for a main dish I usually use about 3 pounds for 4 people. For an appetizer, I think it would depend on what will follow. If it's a light entree, then I might go with 3 pounds for no more than 6 people, stretching it a little further if you have a heartier main course.
Sadly some guests refuse to eat mussels. But more for everyone else.
That would be a nice dinner for my wife, but 1 pound per person is usual. Use white wine or vermouth for the broth with some shallot Peres onion, about of celery and carrot slivers. Serve a nice warm baguette to dip into the broth. Yum yum yum.
Damn iPad autocorrect ...should say red onion.
You can turn off the autocorrect in the settings. I turned it off the first day I had the iPad.
For an appetizer you should feel comfortable serving six to eight people. But then there may be a few bad boys that won't open. These days you don't have to worry about the mud thing as much as mussels are being sustainably farmed (they grow on ropes).
Fortunately (?), I don't know what the "mud thing" is, but do know you still need to remove those beards. Few things worse than eating a mussel, full of anticipation for the taste sensation to come, and chomping on a beard. I've had it happen at restaurants that DEFINITELY should know better!
Beards are really easy to strip off by hand, and in fact I like to see them there. The "mud thing" occurs when mussels are gathered from beds (that's how they live in the real world), mud can collect inside the shell. You can usually tell if it feels heavier in your hand than it should.
I love mussels, so for me that would be dinner for 3 and if arm-twisted, 4. That's assuming there are some nibbles before dinner; the mussels are the entree and some shells won't open; and the only accompaniments are good bread for soaking up the broth and a simple salad of mild greens in a light vinaigrette. I'm smiling because I just had mussels with my nephew at a restaurant recently... It was fun to show him how a friend from France taught me to use an empty shell (one still able to click top & bottom together), as a pincers to pluck the mussel to be eaten from its shell. He loved being given permission to eat with his fingers. Envious of your largesse - bon appetit!
Perhaps we are pigs, but we usually get 3 lbs. for 2 people. That's allowing to throw away some that do not open and with nothing else on the menu except some bread to sop up the sauce.