Effect of the thickness of sowing in the managament of the first feeding of grubs of catfish Sorubim Cuspicaudus

Efecto de la densidad de siembra en el manejo de la primera alimentación de larvas de bagre blanco Sorubim cuspicaudus

In the larviculture of fish, it is necessary the handling of the first feeding to make the grubs viable for the later stages, being the thickness of sowing an important variable in process of production of fries; for which the target of the study was to evaluate the effect of the thickness of sowing in the larviculture of catfish target, at the beginning of the exogenous feeding. Three thickness of sowing were evaluated: 100 (T1), 200 (T2) and 300 grubs/L(T3), fed for six days with cultivated zooplankton (Diaptomus sp, Diaphanosoma sp, Moina sp), offered two times / day; two hours after the feeding, it was siphoned and 40% of water volume was changed. There were used 18 aquariums of four liters of useful volume, six copies by treatment, arranged in a design completely at random. Every day there were realized measurements of dissolved oxygen, temperature and pH; whereas hardness, alkalinity and entire ammonium was measured itself every two days. The profit was estimated in length (Gl), profit in weight (Gp), valuation of specific growth (G), survival (S) and endurance test to the stress (Re). To the minor thickness of sowing (T1) there was obtained the best growth (Gl 6.7±0.2 mm, Gp 7.4±3.9 mg and G 34.2±8.3 % / day). The average values of S ranged between 61.9 (T2) and 65.7 % (T1) and was not observed significant difference (p> 0.05); equally in the test of Re significant difference was not observed (p> 0.05). In T3 there was obtained the biggest productiveness of grubs (186.3 grubs/L) and minor in T1 (66 grubs/L), there being observed significant difference between these values (p <0.05). The results of the present work allow to conclude that to handle the first feeding of the larviculture of catfish target, in the conditions of the experiment, it is more efficient when 300 grubs are sowed /L than to minor thickness.