Lethal reaction of Nile tilapia (Oreochromis niloticus) under low temperature stress.

The present experiment was conducted to study the tolerance of Nile Tilapia to low temperature stress and its duration.Nile Tilapia was continuously stressed by artificial decreasing temperatures and the lethal time of Nile Tilapia under different low temperature stress was recorded.The results showed that the semi-lethal duration of Nile Tilapia was 12.25,17.00,25.00 and 31.50 h(P0.05) under low temperatures of 7,8,9 and 10℃,respectively.That is,the semi-lethal du-ration decreased with decreasing temperatures,however,the mortality of Nile Tilapia was higher at lower temperature stress.The regression equation between death duration and mortality of Nile Tilapia was y =0.0024x2.2453(R2 =0.9667) and y = 0.0013x2.0554(R2=0.9516) at 7 and 8℃,respectively.While it showed linear correlation at 9 and 10℃ temperatures,and the e-quation was y=0.0552x-0.6854(R2=0.9535) and y=0.0288x-0.2875(R2=0.9523),respectively.