Effects of temperature and floating materials on breeding by the paradise fish (Macropodus opercularis) in the non-reproductive season

Effects of temperature and floating materials on breeding by the paradise fish (Macropodus opercularis) in the non-reproductive season. Zoological Studies 45(4): 475-482. The paradise fish, Macropodus opercularis, is native to Taiwan, and its reproductive season spans from Mar. to Oct. This experiment was conducted to examine paradise fish breeding in winter, a non-reproductive season, using different treatments of water temperatures (23, 27, and 31 degrees C) and floating materials (floating ferns, green Styrofoam pieces, and no floating material). The fish built 1-3 bubble nests during the 20 d experimental period. A significant negative correlation was found between the temperature and the frequency of nest building, indicating that a high water temperature of 31 degrees C was unfavorable for building nests. In the treatments with floating ferns and green Styrofoam pieces, the fish built more nests than in the treatment without floating materials. The sizes of the 1st bubble nests built were significantly larger at 27 and 31 degrees C than at 23 degrees C. Floating materials played an important role after the fish acclimated to the temperature. In the treatment with green Styrofoam pieces, the fish built smaller-sized 2nd nests than in the treatment without floating materials. One female in a tank treated at 27 degrees C with green Styrofoam pieces laid 421 eggs during the 20 d experimental period. Two hundred and eighty larvae hatched the next day, for a hatching rate of 66.5%. In short, the paradise fish can breed at appropriate temperatures, such as 27 degrees C, in winter, normally a non-reproductive season, and artificial floating materials are conducive to successful reproduction.