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Fish Survival Rate ( % ) Is Correlated With The Crop Duration

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Shrimp survival rate (%) is correlated with the crop duration in 2012 (p = 0.0006, r = 0.75) and in 2013 (p = 0.0031, r = 0.71). Shrimp yield (kg/ha/crop) was correlated with the crop duration in 2012 (p = 0.0028, r = 0.68) and in 2013 (p = 0.0016, r = 0.74). The crop duration is negatively correlated with average culture period water temperature, while it is positively correlated with CV of hourly water temperature, and with the count of hours fall in the following temperature zones: out of best, out of optimum, and tolerated temperature (Table 4). Of course, when the crop duration is longer, either early stocking or late harvesting, it is extended to cooler days which will lower the average water temperature and increase the temperature variation, and increase the count of undesirable temperatures.
Aeration rate was inversely correlated with daily shrimp production (kg/ha/d) (p = 0.0432, r = -0.36) and positively correlated with FCR (p = 0.0452, r = 0.36); While it was not correlated with all other shrimp production parameters and water temperature parameters (P > 0.05). It is obvious that higher aeration rates are needed when dissolved oxygen levels decrease. This decrease is inversely affecting shrimp growth, survival and production, and is increasing the FCR. The correlations of all shrimp performance and water temperature parameters with pond surface area to volume ratio were not significant (P > 0.05) which agrees with what was observed by Prapaiwong and Boyd (2012b)
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