Diferentes salinidades no desempenho, histologia do fígado e brânquias de juvenis de colossoma macropomum criados em sistemas de reciculação de água (ras)

Abstract

This study evaluated the effects of different water salinities on the performance and gill and liver histology of juvenile Colossoma macropomum cultured in a recirculating aquaculture system (RAS). A total of 448 juveniles (1.37±0.02g) were distributed across four RAS systems, each with a different water salinity: S0 = fresh water (control); S2 = 2 g of salt/L of water; S4 = 4 g of salt/L and S6 = 6 g of salt/L. Animals were housed at a density of one juvenile/L and fed an extruded commercial diet (45% crude protein) ad libitum at 08:00 and 15:00 h, for 45 days. pH was inversely proportional to salinity, while electrical conductivity was directly related to it (P<0.05). Dissolved oxygen, temperature and total ammonia did not differ significantly among salinities (P>0.05). In general, performance, survival and batch uniformity did not differ significantly among salinities at 30 days of cultivation (P>0.05), and still at 45 days of cultivation for survival and batch uniformity (P>0.05). However, weight and daily specific growth rate were higher than the value estimated by the derivative of the equation at 1.98 g of salt/L and 1.58 g of salt/L, respectively. Apparent feed consumption per fish was inversely proportional to salinity. Weight gain and apparent feed conversion showed a Linear Response Plateau effect, with a constant value up to 4.08 g of salt/L and 3.60 g of salt/L, respectively, and a reduction beyond these salinities (P<0.05). The hepatosomatic index was lowest for S6 (P<0.05). Histological analyses revealed changes in structural components and lamellar diameter of gills, as well as structural components of the liver and hepatocyte area, for the different treatments. Colossoma macropomum can be maintained in salinities of up to 4 g of salt/L without compromising performance and liver and gill function.