STANDARDISATION OF REPRODUCTIVE PERFORMANCE OF THE HIGH VALUE ORNAMENTAL FISH, DISCUS Symphysodon aequifasciatus IN RELATION TO TEMPERATURE

The effect of temperature on reproductive performance of discus was evaluated to standardize the optimum temperature for effective spawning and seed production of this high value ornamental fish.  18 pairs of brooders were placed in tanks of 60 litre capacity, equipped with a plastic strip for egg attachment. The breeding pairs were allowed to spawn at 25^oC, 26.5^oC, 28^oC, 29.5^oC, 31^oC and at room temperature (control) with three pairs for each temperature regime for a period of three months. All experimental tanks except 31^oC and control were kept in air conditioned room where ambient temperature was set at 23^oC. The breeding pairs were fed commercial dry feed (Tetra bits) ad libitum twice a day. Data on the time of spawning, number of eggs laid, number of fertilized eggs, hatching time and number of spawn produced were recorded at each spawning session. The spawn were reared for a period of 12 days along with their parents after yolk sac absorption (to enable mucus feeding) and then isolated. No spawning was recorded in tanks housing brooders that were maintained at a temperature of 25^oC and 26.5^oC. Rate of egg fertilization were highest between 27⁰C and 30⁰C. The egg hatching time decreased significantly with increase in temperature. The results (Table 1) proved beyond doubt that a temperature range of 27.5^oC to 30^oC is optimal for breeding, egg incubation and maximum yield of spawn. This inference is worthwhile for breeders of this high value fish since profit from seed sale may be maximized if optimum temperature is maintained for optimal spawning success.