It may happen if the urban lake is near to estuarine region and over flooded if the freshwater was mixed with estuarine water before. Fish are movable. Oreochromis niloticus might die in the lake, then Cichlidoryrus spp. might tolerate to survive in the gills of H. malabaricus. For example, some sea fish move towards river to breed during spawning season, then the parasites shift to other flora and fauna bodies.