The effect of a commercial bacterial supplement on the high-density culturing of Litopenaeus vannamei with a low-protein diet in an outdoor tank system and no water exchange

The effect of adding a commercial bacterial supplement to shrimp growout fa cilities was studied with respect to shrimp yield and water quality paramet ers. Shrimp (Litopenaeus vannamei) were grown in 12 10.5-m(2) outdoor tanks with no water exchange. Each tank was stocked with juvenile L. vannamei (a verage weight, 1.69 g) at a density of 40/m(2). The shrimp were fed with a 21% protein diet. Six randomly assigned tanks were treated with the bacteri al supplement, which was added five times per week, throughout the test per iod. The other six shrimp tanks, which did not receive the bacterial supple ment, served as controls. The test lasted 14 weeks, at which point the shri mp from all the tanks were harvested. Water quality parameters were tested daily or weekly. Sludge slurries were examined at harvest time. There were no significant differences in the water and sludge parameters between the u ntreated shrimp tanks and those tanks that were treated with the commercial bacterial supplement. The harvested shrimp were weighed and counted to cal culate shrimp survival, mean final weight and feed conversion ratio (FCR). The untreated and bacterially treated shrimp tanks had mean survival rate o f 91 and 93%, mean final weight of 12.17 and 11.69 g, and a FCR of 2.15 and 2.19, respectively. There was no significant difference in these values be tween the treated and untreated tanks. The addition of the bacterial supple ment showed no improvement either in water and sediment quality or in shrim p yield over the untreated tanks. It appears that the natural microbial flo ra in the shrimp tanks was sufficient to maintain high water quality, and s upport the growth and survival of the shrimp, thus fulfilling the task inte nded for the bacterial supplement. Therefore, there was no need for such an outside bacterial intervention. (C) 2000 Elsevier Science B.V. All rights reserved.