养殖密度对食用褐鳟Salmo trutta生长和水质的影响

摘要

Two year old brown trout (Salmo trutta) with body weight of (17.52 ±0.22) g was reared in a flowing cylindrical flat bot-tomed glass steel tank (45 cm in diameter and 60 cm in height) at stocking density of 6.8 (group SD1), 10.4 (group SD2), 14.0 (group SD3), 17.5 (group SD4), 21.0 (group SD5), and 24.5 kg/m3 (group SD6) at water temperature of 5.6 ~ 10.5 ℃ for 70 days with triplication in order to detect the effects of stocking density on the growth performance and water quality to find out the suitable stocking density. No significant effect of stocking density on survival rate of the 2 year old brown trout was observed within the present experimental stocking density, while the net weight of the fish was shown to be increased with the elevated stocking density, with the maximum (116.55 g/(m2·d)) in group SD5. The brown trout in group SD4 had significant higher daily weight gain (0.25 g/d), weight gain rate (102.07%) and specific growth rate (1%/d) than the fish in group SD3(P< 0.05). During the experiment, dissolved oxygen levels (DO) were very significantly decreased with increase in stocking density (P< 0.01), very significantly higher in groups SD1, SD2, and SD3 (10.14 ~ 11.84 mg/L) than in groups SD5 and SD6(9.62 ~ 11.53 mg/L)(P< 0.01). There was significant difference in NO2-level between group SD1(0.02 ~ 0.06 mg/L) and groups SD3, SD5 and SD6 (0.04 ~ 0.06 mg/L) in 29 d and 50 d (P< 0.05), without significant difference during other rearing period (P> 0.05). There was significant lower NH4-NT level in groups SD2 and SD3 (0.17 ~ 0.22 mg/L) than that in group SD6(0.25 ~ 0.38 mg/L)(P< 0.05). The findings indicate that it is recommended that the opti-mum stocking density be 17.5 kg/m3, at least no less than 10.4 kg/m3, for two year old brown trout.%在涌泉水温度5.6~10.5℃下,将体质量(17.52±0.22)g的2龄褐鳟Salmo trutta饲养在流水圆柱形平底玻璃钢(半径45cm,高60cm)水槽中,水深40cm,密度分别为6.8kg/m3(SD1)、10.4kg/m3(SD2)、14.0kg/m3(SD3)、17.5kg/m3(SD4)、21.0kg/m3(SD5)和24.5kg/m3(SD6),每个密度组设3个重复,探讨养殖密度对褐鳟生长的影响.70d的饲养结果表明:本试验范围内的放养密度未显著影响2龄褐鳟的存活率(P>0.05),净增重随养殖密度的增加而增大.SD5组褐鳟净增重(116.55g/(m2·d))最大;SD4组褐鳟的日增重(0.25g/d)、增重率(102.07%)和特定生长率(1%/d)显著高于SD3组(P<0.05).随着养殖密度的增加,溶解氧含量(DO)呈极显著下降趋势(P<0.01),SD1、SD2、SD3(10.14~11.84mg/L)组极显著高于SD5、SD6组(9.62~11.53mg/L)(P<0.05);养殖29d和50d时SD1组NO2-含量(0.02~0.06mg/L)与SD3、SD5、SD6组(0.04~0.06mg/L)差异显著(P<0.05),其他时间不显著;36d后SD2、SD3(0.17~0.22mg/L)组的NH4-NT显著低于SD6组(0.25~0.38mg/L)(P<0.05).比较分析认为,2龄褐鳟的最佳养殖密度应为17.5kg/m3,不要低于10.4kg/m3.