Possible Clues:

• Shilling — another twenty needed for calamari?
• Ika, in a sushi restaurant
• Engineer dismissed by gentleman who's landed day's seafood
• Animal pound
• Crew, not top grade, bring in one sea creature ...
• Creature that squirts ink
• Octopus cousin
• One shilling, then twenty times more animals
• Calamari, essentially
• £6 (not 9) for seafood