Avaliação da biomassa do microcrustáceo Daphnia similis (Crustacea, Cladocera) cultivado com a inoculação da microalga Chlorella vulgaris (Beyrinck, 1890) em água do cultivo de tilápia do nilo em sistema de bioflocos

Abstract

Applied widely in the aquaculture as live food to both fish and crustacean on larvae and juvenis stages because the high nutritional values, the microcrustacean from Daphnia genus are mainstream found out in environments with high content of organic matter, microalgae, bacteria and fungi, and that conditions are similar with that found in biofloc system. In this regard, the biofloc water reuse to Daphnia production becomes an option to environmentally friendly aquaculture system. This research aimed assesses the Daphnia similis culture using wastewater from tilapia farming in biofloc system. The experiment was carried out at Laboratório de Produção de Alimento Vivo – LAPAVI –UFRPE, during 30 days, with three treatments DCCW – D. similis culture in clear water with the addition of C. vulgaris; DCBW –D. similis culture in biofloc water from Nile tilapia farming without C. vulgaris adding; and DCBWC - D. similis culture in biofloc water from Nile tilapia farming with C. vulgaris adding were conducted entirely at random with five replicates each using 20L tanks (42 x 17 x 29 cm), with 12 L of useful volume and stocking density of 9 org.L-1. The culture water from Nile tilapia farming in biofloc system had a carbohydrate:nitrogen ratio of 12:1, 45 day of culture, stoking density of 40 fish.m-3 and mean weight of 30.57 ± 10.04 g, was collected and shared on the experimental units. It were evaluated both water quality and growth variables from the microcrustacean. The water quality variables pH, temperature and total dissolved solids (TDS) showed significant positive correlation (P<0.05) with the densities changes of D. similis by Spearman correlation, in that the temperature obtained the highest correlation (r = 0.59). Statistic differences (P<0.05) were found to specific growth rate (SGR), duplication time (DT), maximum mean density (MXD) and yield (Y) among the treatments, in that DBC achieved a Y of 1,065.8 ± 313.3 org.L-1.day-1 and a DMX 800% higher than DACC treatment. Thus, the use of water from Nile tilapia farming in biofloc system in Daphnia similis culture showed a promising alternative to live food production in the aquaculture