Do fish get lonely?

The lone neon, Preface to a Twenty Volume Suicide Note, is a survivor. He swims the tank in a series of jerky movements, resting every so often against the rocks at the bottom. Sometimes I can't decide if he is slowly dying, or slowly living. He must lead such a lonely life. I wonder if fish get lonely. Does he crave the contact of other fish? Does he long for a companion to live out his fish days with? Is he even a he?
Stephen Harper (my pleco) seems indifferent to the lack of life in the fish tank. He clings to the glass sides and lets the current the filter creates sway his tail ever so slightly. Every so often the neon will swim over to him, seemingly just to bask in the presence of another living thing. Does he feel an overwhelming sense of grief to be the last? Watching as his friends all fell victim to a filter with too much suction, one by one.
I can't imagine being the last. I can't imagine being that alone. I wonder if I'm not just projecting; if the fish really even cares that he is alone at all.
I think I'll buy some more fish.