Possible Clues:

• Tough to get hold of
• Not easy to hang onto
• Mention of Fenland place being devious
• Long and slimy
• Difficult to grasp, as an elongated fish
• Wet and squirmy
• Too wriggly to get hold of
• Wriggly, as a fish
• Too wiggly to hold
• Elusive, in a way