The fish is not the issue

 

The issue is what responsibility this 15-year old has as a guest.

He felt his responsibility to his mother, who was not there.  His action distracted him from, or diluted, the fulfillment of his present responsibility to the host.

Your concern is legitimate.

 

(Did he feel guilty to be among the wealth, while his mother is waiting for him in that shabby surroundings?  Should he feel guilty?  Should he just enjoy himself as the host has intended for him to be?  Has the guilt become a substitute for his responsibility to the host?  Should the mother make him feel quilty, or be happy to see him having a good time by himself?  The answers depend on your values.  Right or wrong is hard to say.)