Possible Clues:

• Bachelor in solitary confinement? One lives in a shell
• A bachelor only taking shellfish
• Mother-of-pearl could have come from sailor on his own
• Unaccompanied sailor has seafood
• Found on Elba, a strange gastropod
• Shell used for decoration
• Seafood sailor has without anything else
• Marine mollusc sailor single-handedly gathered
• Seafood sustaining sailor on solo voyage?
• A learner tucking into a dog's dinner or some seafood?