Effects of different low temperature continuous stress on Litopenaeus vannamei survival.

【Objective】The tolerance of Litopenaeus vannamei against low temperature continuous stress was tested to provide scientific references for evaluating risks caused by low temperature for Litopenaeus vannamei breeding industry and cold disaster relief measures. 【Method】The experiments were conducted at 6 different low temperatures, viz., 7, 8, 9, 10, 11 and 20℃(control). Through observing the response of Litopenaeus vannamei to low temperature stress and recording the death duration, the mortality rate and lethiferous period were statistically analyzed and set up a relation model. 【Result】 During the experiment, the survival rate of the Litopenaeus vannamei in the control group was 100% meaning there was no death. The results of the experimental group showed that within certain low temperature range, the higher temperature, the longer death duration at the first and 100% mortality; for example, sustaining stress at 7℃, the death duration at the first and 100% mortality was 2.6 and 13.3 h, respectively, but at 11℃ , it was 27.0 and 158.4 h, respectively. Litopenaeus vannamei was sensitive to low temperature. At the temperature range of 7-11℃, sustaining cold stress induced mortality, but the death duration from the first to 100% was different: it was 24.4 h at 7℃ and 145.1 at 11℃ , respectively. With lower temperature, the mortality period was shorter. The confidence coefficient in the regression equation of mortality rate and death duration was over 0.9500. At 7, 9 and 11℃, the survival rate and death duration conformed to power function equation with the power function index of 1.2751, 1.0508 and 1.117, respectively. While at 8 and 10℃, the survival rate and death duration were in line with polynominal equation. 【Conclusion】Litopenaeus vannamei is unable to endure low temperature; its cold-lethiferous period lasts for a range, and the death speed accelerates with the decreasing temperature. That suggests that emergency management should be enhanced in cold seasons so as to fend off cold risks. The duration managed to avoid cold-dependent mortality under 7℃ was no longer than 24 h; at the temperature over 11℃, there are at most 6 days for emergency management.