I grew up eating fish on Friday because I lived in Wisconsin. I have no explanation for that, other than It's What You Do. Of course, in the U.K., you could have fish and chips every day of the week and twice on Sunday. (or Friday.)
(As it happens, fish and chip shops aren't overabundant in Cambridge, and the couple I've sampled are just OK. Pub fish & chips are better.)
Anyway, this was my fish & chip dinner on this fine Friday, also featuring mushy peas. Darn tasty!