The effect of pH on sex ratio, gonadal devolopment, growth and survival rate in zebrafish ( Danio rerio)

In this thesis, the effects of different water pH levels on zebrafish (Danino rerio) sex ratio, gonadal development, growth and survival rate were investigated. The principal goal of the research was to evaluate an environmentally friendly method for mono-sex population in zebrafish. Different concentration of water pH levels (6; 6,5; 7; 8; 8,5, and 9) were tested by immersion of newly hatched larvae for a duration of 3 months. The experiment was performed as six groups with three replications and was carried out in 18 aquariums with the dimensions of 22x18x9cm. The water temperature maintained at 28±0.33°C in all treatment groups. Of the water pH levels used in the present stdudy, the water pH level 9 groups were the most effective in terms of masculinization, resulting in a maximum male ratio of 100% (p<0,001). Sex ratio of 25 and 82.35% at water pH levels 6 and 8,5, respectively, were also significntly different from the expected 1F:1M ratio (p<0,05). Histological examination revealed that the gametes of fish at low water pH levels entered early maturation stage than at higher water pH level groups. Some deformalities in the gonads at low water pH level groups were also detected. The best growth, gonadal development and survival rate were recorded in the water pH level 8 groups. Survival rate were lowest in the water pH level 9 groups. It was suggested that at low pH level feminisation (for female production) and/or at high water pH level masculinisation (for male production) for monosex production of zebrafish can be used. For maximum growt, gonadal development and survival rate water pH level 8 was suggested.