We fish often around the Ntfufu area just North of Port St Johns and we have found the same effect from eating Bronze Bream. Apparently at certain times of the year they eat a seaweed with halocionegenic properties that effects humans. The locals call it the dream fish due to the vivid dreams you have after eating it.
For years we used to wake up in the middle of the night high as a kite thinking there must me a gas leak in the house.