According to a friend of mine who works closely with the fishermen in the city, the kuppam in Triplicane has an interesting story about their relationship with the Parthasarathy Temple there. The fishermen claim that the temple actually used to be theirs, but that they ceded control over it a long time ago, although they still participate in many of the temple rituals. Ironically, the temple board is now claiming that the fishermen are encroaching on temple land, so the fishermen are fighting to stay on land that was once all theirs.
This makes sense. Even the Kapaleeswar Temple in Mylapore apparently used to be located right on the seashore. It, too, must have been a fishermen’s temple before it was moved inland.