I don't know if this is a tuna or some other kind of large fish, but he better watch out. That bull is just about to step on him!
Not an expert, just my guess... Kingdom of Sicily, AE Denaro, 13th-14th century? Something like this perhaps : http://www.cngcoins.com/Coin.aspx?CoinID=22862 I don't see tuna in this coin though .