"Everyone uses mussels for bait"
Mussel: Miesmuscheln-2
GNU Free Documentation LicenseMussel: Miesmuscheln-2 - Credit: Rainer Zenz

Barnacles and Mussels and a Bit of Plastic
Creative Commons Attribution Share AlikeBarnacles and Mussels and a Bit of Plastic - Credit: garlandcannon
 Mussels are a type of clam. They have a hard shell exterior with a soft, rubbery and often edible interior. They are indeed used as bait and are recommended for cod fishing, especially as they are freely available.