| Summary: | 碩士 === 國立高雄海洋科技大學 === 漁業生產與管理研究所 === 97 === 1. Low temperature is the main cause affecting milkfish(Chanos chanos) cultivation. Ten tests of temperature reduction have been done repeatedly in this research from 25℃ to 11℃. At 16℃, the whole group of milkfish drops to the pool bottom and one of them dies. At 15.0℃, 2% of them die. At 14.5℃, 10% die. At 13℃, 100% die. As a result, 13℃ is the fatal temperature for milkfish.
2. Output of single milkfish cultivation in Taiwan is 36,500 tons. Total stocking area is 9,617.9 hectares. Critical output is 3,795 kg/hectare. At average adult milkfish of 0.8kg/each, appropriate stocking density is 4,743.75 milkfish/hectare. This proves single cultivation model of 5,000 milkfish is appropriate. Based on critical price of NTD50/kg, the average price of NTD46.05/each in the pat 16 years is making single cultivation industry in difficult situation.
3. Total cost of polyculture of milkfish and white shrimp(Litopenaeus vannamei) is NTD624,780 and total revenue is NTD826,700 with net profit of NTD201,920 at E/P ratio of 32.32. It is better than that of traditional cultivation industry at 14.86. Milkfish price has been decreasing in recent years. To select larger milkfish fries with white shrimps to have polyculture of the two for one year and two seasons will bring maximum profits.
4. The density of 10,000 milkfish and 1.05 million white shrimps per hectare does stabilize water quality and enables milkfish and white shrimps to grow steadily. The tension on bred species is also eased. Death rate is reduced, indirectly making milkfish and white shrimps grow quickly. The cultivation period in summer is around 2 months shorter than that of traditional cultivation industry.
5. Polyculture of the two do reduce white shrimp cultivation cost to NTD17.87/kg and increase overall profits. It is suggested the industry try the cultivation model for higher profits.
6. Purchase price of milkfish and white shrimps through winters is higher between October and November. Milkfish fries over 3” and white shrimps fries are mixed and harvested before Tomb Sweeping Day. This will increase revenues of sales of milkfish and white shrimp in the 2nd stage. With higher poolside price after winter, traditional cultivation industry can adjust operation model to enhance yearly profits.
7. Based cost output elasticity, under increased output of milkfish cultivation industry for1%, total cost increases 0.731%; polyculture of milkfish increases 0.817%. Milkfish fries cost has greatest changes, followed by cost of feeds. When monoculture of milkfish fries goes up by 1%, total cost increases 0.451%; polyculture cost of milkfish fries increases 0.315%.
8. The major source of milkfish fries is from Taiwan Milkfish Cultivation Field. The industry can buy first batch milkfish fries at the beginning of 2nd quarter to harvest in July/August. The 2nd batch of milkfish fries is bought at the end of 3rd quarter to go through winter. In this way, milkfish fries is bought at lower cost to minimize impacts of higher cost. Cost elasticity of feeds is the second most important factor after cost of milkfish fries. The input cost elasticity of monoculture is 0.191% and that of milkfish polyculture is 0.138%.
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