If deep ponds are not mixed, large volumes of oxygen depleted water will accumulate near the pond bottom due to thermal stratification. Stratification occurs during the warm season when warmer, less dense water remains near the pond's surface. Water which is too deep to receive much sunlight becomes cooler and often deficient in dissolved oxygen. Cool water is more dense than warm water and remains near the pond bottom. Without adequate water circulation, much of the bottom habitat available to the prawns could be eliminated due to the absence of dissolved oxygen.
Individual size decreases as stocking density increases.
Since, substantial pond bottom habitat may be lost due to the presence of anoxic waters in stratified ponds, stocking density may have to be reduced to obtain marketable sized prawns. Low D.O. may cause prawns to crawl out of the ponds or congregate at the pond edge during daylight. This will increase their vulnerability to predation. Prawns can tolerate temporary low D.O. conditions, however exposure should be avoided if possible. Dissolved oxygen meters should be used to monitor D.O. in the early evening hours and before dawn.