应用于工厂化养殖的凡纳滨对虾耐流性研究

Research on flow resistance of Litopenaeus vannamei related to industrial culture

工厂化对虾养殖中,需要根据对虾耐流性,并结合污物聚集效果调控池内水流速度大小和持续时间长短。本研究利用垂直循环水槽,分别测定5种流速(20. 3、23. 0、30. 2、34. 9和41. 3 cm/s)下凡纳滨对虾(Litopenaeus vannamei)[(3. 62±0. 50) g]的可持续游泳时间,并以此为指标衡量凡纳滨对虾相应流速下的耐流性。结果显示:同一流速下,外部特征相似的凡纳滨对虾可持续游泳时间具有较大的个体差异性;个体差异性的表征参数(离散系数)随流速的增大先增大后减少,在34. 9 cm/s时达到最大;由累积疲劳比例随时间的变化关系曲线可知,高流速(30. 2、34. 9和41. 3 cm/s)试验组中,接近50%的对虾会在10 min内因疲劳触网而不能继续游泳;曲线拟合决定系数R2显示,指数函数能最好地呈现平均可持续游泳时间随流速的变化关系。研究表明,工厂化养殖中水流调控要考虑对虾耐流性的个体差异性,而不是仅考虑对虾的平均耐流性。对于本研究所用的对虾(3. 62±0. 50) g,池内流速建议控制在30. 2 cm/s以下,并且参考累积疲劳比例随时间的变化关系曲线,确定相应流速下的水流持续时间。

In industrial shrimp culture,it is necessary to control the flow velocity in the pond and the duration of the flow according to the flow resistance of the shrimp and in combination with the effect of the accumulation of pollutants.In this research,vertical circulation flume tank was used to measure the sustainable swimming time of Litopenaeus vannamei(3.62±0.50 g)under five flow velocity levels(20.3,23.0,30.2,34.9 and 41.3 cm/s),and the time was taken as the index to assess its flow resistance at corresponding flow velocity.The results showed that at the same flow velocity,the sustainable swimming time varied significantly among the shrimps having similar external characteristics.The characterization parameter for the variation(coefficient of variation)increased and then decreased with the increasing flow velocity,peaking at 34.9 cm/s.The relationship curve of cumulative fatigue percentage and swimming time indicated that for the high velocity cases(30.2,34.9 and 41.3 cm/s),nearly 50%of the shrimps got fatigue within 10 min and could not swim anymore.The coefficient R^2 for curving fitting showed that exponential function could express the relationship between average sustainable swimming time and flow velocity best.The findings in this research suggested that it is not only to take the average flow resistance of shrimp but also the variation of flow resistance among shrimps into consideration when performing the flow control in industrial culture.For the shrimp(3.62±0.50)g used in this research,the flow velocity in the pond should be controlled below 30.2 m/s,and the duration of the flow at corresponding flow velocity should be decided based on the relationship cure of cumulative fatigue percentage and swimming time.