Pond Wars: Raccoons vs Goldfish

Hello all,
   This is very much off of the topic, but an interesting problem
    I have a friend who has kept goldfish in his small pond for 3 years
without problems.  Recently, though, raccoons have eaten most of his fish.
 He had several generations crowded into his little pond.  Now he has three
    I am going to loan him a spare 15 gallon to keep the survivors in over
the winter (he had wintered them outside in previous seasons).  In the
spring, what can he do to keep the raccoons out of his pond?  I suggested
perhaps raising the edge a foot or so, but this was only to prevent him from
enclosing the entire thing in chicken wire.  I am actually completely
      Any help would be VERY much appreciated by both my friend and I.
 Again, I'm sorry to pollute the APD with this off topic problem, but I trust
you folks.
                Tony Thorpe