California-Italian Fish House (or an Italian Fish House located in California).

"Pesci"= Plural Italian for Fish.
So, "Capesci".

Then the word is a play off "Capisci", which is the Italian (tu) form of the verb "Capire", which means "to know or understand". Capisci / Capesci. It's all the same in the proposed taglines:

"You Know Fish. So Do We."
"You Know Fish."