Effect of rock salt salinity on morphometric and physiological Changes of Nile Tilapia (Oreochromis niloticus Linn.)(Thai)

Abstract

The purpose of this study was to investigate the effect of rock salt salinity on morphometric and physiological changes of Nile Tilapia (NT) (Oreochromis niloticus). A completely randomized design was used. Two hundred NT were divided into five groups (forty NT per group) and five replications. Group one was maintained in normal water. Groups two, three, four and five were maintained in water that had rock salt added at 10, 20, 30 and 40 g/l, respectively. Each group of NT was raised for 45 days. On days 1, 15, 30 and 45 of the experimental period, the respiratory rate of ten NT in each group was determined. On day 45, morphometric (total length, body length, head length and body width) and white blood cell parameters (neutrophil, lymphocyte, monocyte and eosinophil) of ten NT in each group were measured. The results showed that all NT maintained at 40 g/l of rock salt salinity died at an early stage of the experiment. Total length, body length and head length of NT in groups one, two, three and four were not significantly different (p>0.05). Body width of group two was significantly lower than group one (p<0.05). The respiratory rate of groups three and four were significantly higher than groups one and two (p<0.05). The percentage of monocytes in group four was significantly higher than groups one and two (p<0.05). These phenomena show that NT maintained in water with more than 30 g/l added rock salt were under salinity stress.