Growth, feeding factors and the effect of salinity stress on thesurvival rate on roach (Rutilusrutiluscaspicus) juveniles fed with different levels of betaine and tryptophan

The effect of different levels of betaine and tryptophan on growth and resistance to salinities in the Caspian roach was investigated. Fish (1.90 ± 0.04 g body weight) were divided into 9 groups (4 treatments groups containing betaine (0.5 and 1), tryptophan (0.25 and 0.5), betaine and tryptophan mixtures (0.25- 0.5, 0.25, -1, 0.5-0.5 and 0.5- 1), and control group). After recording the growth factors, the fish were exposed to salinities (12, 16 and 20 ppt) and clinical symptoms and mortality rate were recorded. No mortality occurred in 12 ppt salinity. At 16 ppt, the lowest mortality (16.66%) was recorded in the treatment containing 1% betaine and 0.5% tryptophan, while the highest mortalty (59.98%) occurred in the control group. At 20 ppt salinity, 100% mortality occurred within 6 hours in the control, while in the other treatments 100%-mortality occurred after 24 hours. Behavioral symptoms, such as jerky movements, ataxia, increased respiratory rate, were more prominent in higher salinities. Tryptophan did not reduce food consumption meaningfully. Increaesd food consumption as the result of betaine did not show significant effect on the fish growth rate.