Consequences of Decreased Water Temperature Caused by Aerator-Induced Evaporation on Growth of Pacific White Shrimp Litopenaeus vannamei in Ponds

Abstract

Two studies were performed related to water temperature in aquaculture ponds. The first study evaluated the influence of aeration on evaporation and water temperature in ponds, and compared the effects of daytime and nighttime aeration on pond evaporation and water temperature. Water temperature and water loss by evaporation were monitored in ponds with different rates of aeration (9.2, 18.4, 27.6 and 36.9 kW/ha). The mean decrease in water temperature at 70-cm depth was greater than that at the surface in aerated ponds than in control ponds. Nevertheless, the mean decrease in water temperature at 70-cm depth was greater during daytime aeration than during nighttime aeration. The decrease in surface temperature was greater during nighttime aeration than during daytime aeration. The greater the aeration rate during either day or night, the cooler was both surface and water at 70 cm. Increasing the aeration rate also increased pond evaporation. Pond evaporation increases water loss by 32 and 92% over 24 h in ponds aerated with one and four 0.37-kW Air-O-Lator aerators, respectively. The nutrient-enriched control pond was more turbid, had cooler surface and deep water temperature, and had greater evaporation loss than the control pond without nutrient addition and less turbid water. The second study determined water temperature patterns on a shrimp farm in different ponds and different years and revealed the effects of bottom water temperature in ponds to variation in shrimp performance. The study was conducted at Greene Prairie Aquafarm located in west-central Alabama. Water temperature at 1.2 m depth in 22 ponds and air temperature were monitored at 1-h intervals during the 2012, 2013, 2014 and 2015 growing seasons. Records of stocking rates, survival rates, and production were provided by the farm owner. Correlation analysis and linear mixed model analysis of variance were used. Results showed that the hourly water temperatures were different among ponds. The range of water temperature in each pond explained 41% of the variance in average final weight of shrimp harvested from each pond. In conclusion, results suggest that variation in water temperature patterns has a major influence on shrimp performance in ponds.