Influência das baixas salinidades na composição microbiana e no desempenho de Juvenis de Litopenaeus vannamei cultivados em sistema super-intensivo sem Renovação de Água

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Considered environmentally friendly, due to minimal water use and effluents emission, the production systems performed without water exchange present the additional advantages of the possibility of rearing marine shrimp far from the valued coastal zone and close to consumption centers, as well as supplementation of the animals diet through their characteristic microbial community. The shrimp Litopenaeus vannamei, due to accelerated growth and tolerance to a wide range of salinities, represents a species of interest to rearing in such production systems. In this context, the objective of this study was to evaluate the influence of salinity on water quality, microbial composition and performance of L. vannamei juveniles reared in system without water exchange. The experimental system was installed inside a greenhouse and consisted of 16 circular tanks (bottom area of 0.36m2) with useful volume of 163L. Groups of 110 shrimps, with initial mean weight of 0.24 0.08g, were randomly distributed in the experimental units (300 shrimps/m2) and reared during 40 days at different salinities (0, 2, 4 and 25) with four replicates each treatment. Prior to the stocking, during 10 days the shrimps were properly acclimated to the different salinities. The feeding (commercial diet - 42.5% CP) was performed through feeding trays, twice daily, in an initial rate of 8% of the biomass in each tank with posterior adjustments according to the observed consumption. The physical, chemical and biological water parameters (temperature, dissolved oxygen, salinity, pH, alkalinity, ammonia, nitrite, nitrate, phosphate, total suspended solids and chlorophyll a) were monitored periodically. The microbial community present in the different salinities was characterized and analyzed as its proximate composition. The animals performance (final weight, weight gain, specific growth rate, final biomass, total individual feed consumption, feed conversion and survival) was evaluated. The most of the water quality parameters was not significantly influenced by salinity, except for total suspended solids concentration and pH. Despite no significant differences (P>0.05), it was observed a tendency of intensification on the nitrification process according to salinity increase, and lower values of ammonia and higher values of nitrite and nitrate were obtained at the highest salinity (25). It was verified a tendency of reduction on ciliates concentration and increase on flagellates concentration according to salinity increase. The microalgae were predominantly represented by diatoms in the highest salinity and by chlorophytes in lower salinities. The crude protein percentage in microbial flocs reduced according to salinity increase, whereas the ash content showed inverse tendency. Survival, final weight, final biomass and total individual feed consumption were positively influenced by salinity increase (P<0.05). The others performance parameters, although also tended to improve with increasing salinity, did not differ among treatments (P>0.05). In the present study, better results were obtained with L. vannamei juveniles reared in system without water exchange at salinity 25; however, satisfactory productivity was also verified at salinity 4, suggesting the viability of implementation the culture at low salinity.

ASSUNTO(S)

zootecnia vannamei sistema sem renovação de água salinidade recursos pesqueiros aquicultura

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