The fish is a symbol of christianity. There is not only the fish in the freezer, if you pay attention fish symbolism is all over the film. The picture of him and the welder is when he caught the tuna in the freezer, over a year ago. There are many other instances the bumper sticker, fish paintings in marie's house, even in his pencil bowl there is a rubber fish. The significance the the christian theme ties into the plot, Reznik has guilt because he killed the child in a hit and run. Several times throughout the movie he comes to a fork in the road where he has to choose a path, the right side is illuminated which represents justice and salvation. The left path is dark, the way to hell. Reznik goes left on three different occasions, spiraling deeper into chaos. The character Miller also strengthens the Christian theme, he is easy to forgive Reznik for the loss of his arm, something that is not easy to do, he provides a Christian example. Reznik is played by Christian Bale which is pretty weird too. This film deserves more credit then it gets. It's full of symbolism and the look and cinematography are quite interesting throughout, lot's of meaningful composition. Not to mention one of the best paced modern thrillers, it defiantly has a tone and pace reminiscent of Hitchcock films, complete with the post it note McGuffin. Brad Anderson one ups Hitchcock by actually incorporating the McGuffin into the resolution. Brilliant filmmaking one of my new favs.