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Browsing by Author "Poersch, L. H."

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    The Effect of Solids Removal on Water Quality, Growth and Survival of Litopenaeus vannamei in a Biofloc Technology Culture System
    Gaona, C. A. P.; Poersch, L. H.; Krummenauer, D.; Foes, G. K.; Wasielesky, W. J. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2011-06-01)
    Biofloc technology culture systems can increase the productivity of shrimp culture. Through the use of minimal or zero exchange, biofloc technology culture systems can also reduce the use of water. Diet enhancement through the addition of feed increases the amount of excreta. Together with unconsumed feed, the additional excreta increases the amount of suspended solids and reduces the concentration of dissolved oxygen. In addition, the excess of suspended solids can harm the culture by reducing light penetration. In turn, the lower light levels reduce the abundance of photosynthetic organisms (microalgae) that are also important for water quality and shrimp nutrition. The objective of this study was to evaluate the removal of suspended solids from the water of the culture system by a clarification process (i.e. particle settling). Two treatments were applied: with clarification and no clarification. Six tanks, each 35 m³, were used in the study. In the clarification treatment, 35 m³ of water with bioflocs was pumped from the experimental unit for 6 hours. The water passed through a settling tank (1,000 L) and was returned to the culture unit through gravity. The clarification treatment reduced total suspended solids (24.5%), turbidity (27%) and chlorophyll a (27.8%). The availability of dissolved oxygen and pH values were also greater in the clarification treatment. Growth, feed conversion ratio, survival and productivity were significantly higher (p<0.05) with the removal of suspended solids. Control of the concentration of suspended solids contributed to the improvement of water quality and the growth performance of the shrimp L. vannamei in the superintensive biofloc technology culture.