匙吻鱘養殖生物學之研究

Abstract

匙吻鱘屬於北美洲特有種的大型淡水魚類，主要分布於密西西比河主要流域， 其魚肉和魚卵和一般鱘一樣具有高商品價值，尤其是被稱為黑色黃金的鱘魚子醬，更是價值不斐，匙吻鱘屬於濾食性動物，成長快速、存活率高，近年來為養殖市場的新寵兒。本實驗的研究目的為針對育苗及育成部分做基礎生物學之研究。 實驗一探討水深對匙吻鱘攝食之影響，使用平均為15公克的匙吻鱘為試驗材料，以水泥池流水式飼養，每組10尾，二重複，分別測試匙吻鱘能否接受沉性飼料，及匙吻鱘對於水深對於匙吻鱘攝食浮性飼料之影響，結果顯示匙吻鱘無法攝食沉飼料，但對於水深的要求並不嚴苛，在40公分以上的水深時，匙吻鱘即可正常攝食浮性飼料。 實驗二探討投餵次數對匙吻鱘攝食及成長之影響，使用平均為5公克的匙吻鱘為試驗材料，採水泥池流水式飼養，每組5尾，二重複，以每天固定100顆飼料量的前提下，分為每天投餵2、4、6、8等不同的投餵次數，在計算其殘餌量，結果顯示每天投餵6次和投餵8次對於匙吻鱘的成長為最佳，而殘餌為最少。 實驗三探討不同照度環境下對匙吻鱘攝食之影響，使用平均為5公克的匙吻鱘為試驗材料，採水泥池流水式飼養，每組5尾，二重複，將匙吻鱘置於500lux、1000lux、2000lux、4000lux等不同照度環境下探討對匙吻鱘攝食之影響，結果顯示，500lux、1000lux的環境下，匙吻鱘可以維持正常的攝食行為，而在另外兩個照度下則否。 實驗四探討不同鹽度對匙吻鱘存活之影響，使用平均為5公克的匙吻鱘為試驗材料，以FRP桶飼養，每組5尾，二重複，實驗分為直接將匙吻鱘放置於5、10、15、20ppt的環境下，在96小時內記錄匙吻鱘的行為變化，另外以逐步增加鹽度，每天增加1ppt、階段性增加鹽度，在第1天時加至4ppt適應3天後增加3ppt再3天增加3ppt，突然增加鹽度，每5天增加5ppt等三個不同增加鹽度的方法增加鹽度到10ppt為止，測對匙吻鱘存活之影響，結果顯示在10、15、20ppt等組別，匙吻鱘均會依序出現以下的行為：1.緩慢繞養殖FRP桶游動。2.快速游動，甚至衝撞養殖FRP桶。3.活動明顯減弱，慢慢下沉到FRP桶底部，並且慢慢失去平衡。4.停止活動死亡。而在5ppt的環境下匙吻鱘則沒有出現異常行為，在三種不同的增加鹽度方法中，以逐步增加鹽度的方法為最佳，其餘兩個方法皆會造成匙吻鱘的死亡。 實驗五探討商業飼料對於匙吻鱘成長、存活及體組成之影響，使用平均為20公克的匙吻鱘為試驗材料，每組10尾，以水泥池流水式飼養，分別餵食鰻魚浮性飼料粗蛋白質為45％(高蛋白組)，粗脂肪為11％，吳郭魚浮性飼料粗蛋白為28％(中蛋白組)，粗脂肪為6％，虱目魚浮性飼料粗蛋白為24％(低蛋白組)，粗脂肪為6％，測試增重率、日成長率、飼料換肉率、存活率、體組成等部分，實驗進行120天，結果顯示不管是在增重率、日成長率、飼料換肉率上，皆以投餵鰻魚飼料的高蛋白組為最佳，另外兩組則是無顯著性差異，且鰻魚飼料有較高的EPA及DHA，也有助於提升魚肉中EPA及DHA的含量。總結匙吻鱘無法攝食沉性飼料，在攝食浮性飼料上對於水深要求不高，只需要40公分以上即可正常的攝食，而且可以耐受5-10ppt的鹽度，並且可利用控制照度促進匙吻鱘攝食，在飼料的選擇上面以鰻魚浮性飼料對於匙吻鱘的成長效果最佳，而投餵次數以每天6次為最佳，可有效減少殘餌。

Paddlefish, one of the largest freshwater fish, are endemic to most river and tributaries of Mississippi basin and are found in 22 states in United States. Paddlefish, like sturgeon, are highly valued for its grayish-black roe that is processed into caviar and for their boneless, firm, white meat. Paddlefish have many outstanding characteristics as a food fish. Paddlefish filter feed primarily on zooplankton throughout most of their life and grow rapidly, also have high survival rate .Aquaculture of paddlefish is attracting increasing attention as an aquaculture species. A study is conducted examining the culture biology of paddlefish. The first experiment was conducted examining the influence of water depths for feeding regimen of paddlefish. Twenty paddlefish juveniles of mean weight 15g were randomly stocked into cement ponds with flow in order to test the restriction for feeding paddlefish pellets from the bottom and the effect of water depth on floating pellets were fed. Results show that paddlefish cannot consume pellets from the bottom, and paddlefish can only be fed when the water depth is deeper than 40 cm. The second experiment was conducted examining growth and feeding regimen of paddlefish as different times of pellets was fed a day. Twenty paddlefish juveniles of mean weight 5g were randomly stocked into cement ponds with flow. Paddlefish were fed one hundred pellets a day, but they were fed in twice, four times, six times, eight times a day, respectively. After measuring remnant of pellets, the result shows that paddlefish is fed six times and eight times a day the most adequately and there are less pellets left. The third experiment conducted examining the effect of different irradiances on feeding regimen of paddlefish. Twenty paddlefish juveniles of mean weight 5g were randomly stocked into cement ponds with flow under the irradiances of 500lux, 1000lux, 2000lux, and 4000lux respectively. The result shows that paddlefish can maintain normal feeding regimen under the irradiances of 500lux and 1000lux but not the irradiances of 2000lux and 4000lux. The fourth experiment conducted examining the effect of different salinity on survival of paddlefish. There was two phases in this experiment. Phase I: twenty paddlefish juveniles of mean weight 5g were randomly stocked into FRP tanks and 5ppt, 10ppt, 15ppt and 20ppt of salinity respectively. The activity of paddlefish was recorded within following 96 hours. Phase II: three different ways to increase the salinity was implemented in reservoirs. One was to increase 1ppt of salinity daily until the salinity of water reaching to 10ppt. Another was to increase 4ppt on first day, and wait for three days, and then increase 3ppt every three days until the salinity of water was 10ppt. The other was to increase 5ppt every five days until the salinity of water was 10ppt. The result shows that paddlefish in 10ppt, 15ppt, and 20ppt tanks will present following reaction accordingly: 1. Paddlefish would swim around the reservoirs, FRP tanks, slowly. 2. Paddlefish would swim fast, or even strike themselves against the tanks. 3. Paddlefish would move slowly down to the tanks and lose their balance. 4. Paddle would stop moving and die in the end. However, in the tank of 5ppt of salinity, there were no abnormal activities shown for paddlefish. The result also shows that the best way of raising salinity in water is to increase 1ppt of salinity daily, and the other ways will cause the death of paddlefish. The fifth experiment conducted examining the effect on growth, survival, and fillet composition of paddlefish when fed commercial feeds differing in protein and lipid level. Thirty paddlefish juveniles of mean weight 20g were randomly stocked into cement ponds with flow, and were fed floating commercial eel feeds (45% protein, 11% lipid, the highest protein), commercial floating tilapia feeds (28% protein, 6% lipid, the medium protein), and commercial floating milk fish feeds (24% protein, 6% lipid, the lowest protein) respectively. The paddlefish were harvested after 120 days. At harvests, it shows there are no differences in relative growth, specific growth rate, feed conversion rate, percent survival, and fillet composition of paddlefish between the medium protein and the lowest protein treatments. Yet, the ratio is significant higher for paddlefish fed the eel feed (the highest protein treatment) compared with the others. Paddlefish fed the eel feed contain much EPA and DHA because of higher EPA and DHA of eel feed.