臺南虱目魚之生態研究

Abstract

1. 氣壓變化與虱目魚池溶氧瞬度無關。 2. 氣溫與虱目魚池水溫間的差異因水深而增加。 3. 週日間的溶氧濃度隨著溫度而增加。 4. 混濁度較高者則溶氧濃度較低。 5. 日照量多則溶氧量高。 6. 溶氧量週日的變化隨各測定時間而有極顯著的差異。 7. 底藻的燒失量與溶氧濃度均因飼養日期愈久而愈少。 8. 底藻的多寡與溶氧量有顯著的正相關。 9. 虱目魚苗的致死溫度；高溫為42.7℃以上，低溫為8.5℃以下。 10. 虱目魚的耗氧量因魚體的大小而有異，致死濃度約0.11ml/l至0.25ml/l之間。 11. 虱目魚苗的抗鹽力極強，其致死鹽度大約為108.6±7.82?。 12. 虱目魚之消化道為體長的倍數，大魚較小魚的倍數為大。 13. 虱目魚的消化系統屬於攝食底藻與浮游生物者。夜間或清晨幾乎攝食動物性浮游生物，書間則主食Lyngbya；於養殖期末主食Chroococcus 14. 消化道內含物與體重的百分比和溫度的週日變化有顯著的正相關。 15. 消化道內含物與體重的百分比經Bliss表轉化後隨時間的不同而有顯著的差異。 16. 於五月所得的資科：溶氧量，水溫和消化道內食物與體重之百分比有正相關。 17. 於五、六月所得的資料，虱目魚體長與體重的關係式為W=0.0000009811•(F.L.)3.07299316 18. 五、六月虱目魚的肥滿度較十月的略大，各為14.7238±1.2683與14.0247±0.7262，兩者之間有顯著的差異。 19. 於十月測得的溶氧量之週日變化絞小（0.00-5.36 ml/l）終日消化道內均存內含物。其含量之多寡與溶氧量的多寡有一致的趨勢。於五月溶氧量的週日變化大（0.36-14.78ml/l）時，溶氧量3.2ml/l以下食量極少以上則食量大增。 20. 如七月資料所得，溶氧太低的魚池則虱目魚易於死亡。

1. There is no correlation between the atmospheric pressure and dissolved oxygen concentration in milkfish pond. 2. The water temperature of shal1ow wilkfish ponds is more easily inflennced by air temperature than deeper ponds. 3. The diurnal fluctuation of dissolved oxygen concentration follows quite closely to the water temperature. 4. The higher the water turbidity, the lower the dissolved oxygen concentration. 5. The greater the sum of the diurnal duration, the higher the concentration of the dissolved oxygen. 6. The dissolved oxygen concentration varies with the time of the day. 7. Pettom algae decreases with the advance of culture period, and so is the dissolved oxygen concentration. 8. The correlation of dissolved oxygen and abundance of bottom algae is significantly positive. 9. The lethal temperature for juvenile milkfish lies above 42.7℃ and below 8.5℃. 10. The oxygen consumption of milkfish varies according to body weight; the lethal concentration is 0.11-0.25 ml/l. 11. Milkfish is euryhaline; the maximum lethal salinity for juvenile milkfish is 108.6 ± 7.82 per mille. 12. The ratio of the alimentary canal and the body length of milkfish is smaller in juvenile than in adult. 13. The disestive system of milkfish is adapted essentially for benthic alga and plankton feeding. The food of mildfish varies with time; during night and early morning the milkfish feeds almost all on zooplankton. In day time it takes essentially Lyngbya and in the later part of the culture period Chroococcus. 14. The weight of the content of the digestive tract as percentage of the body weight is significantly correlated to the diurnal fluctuation of the water temperature. 15. The above percentage after transformed into degrees of angle by Bliss, shows a significant difference in different time of the day. 16. Data obtained in May show that dissolved oxygen concention, water temperature and alimentary content in percentage of the body weight are positively correlated. 17. The relationship of body weight and body length (fork length) of mildfish calculated from the data of May and June can be expressed by the equation: W=0.0000009811•(F.L.)3.07299316 18. The degree of well being of milkfish in May and June is better than that in October, I.e. 14.7238±1.2683 against 14.0247±0.72615 respectively, this difference being statistically significant. 19. When the range of oxygen concentration is small during the month of October the alimentary canal content varies little showing poor digestion due to insufficient supply of O2. But when the range of O2 concentration is wider (for example between 0.36 and 14.78ml/l.)the content of alimentary canal varies to great extent, signifying that the fish almost stop eating at low level of O2 content and begin to eat vigorously and digest rapidly at higher level of O2 conantration. 20. As shown by data obtained in July, the milkfish is apt to die gradually because of low dissolved oxygen concentration.