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The Effect of Low pH Level on Zebrafish (Danio Rerio) Reproductive Performance

Danio rerio or commonly known as zebrafish are a very popular fish among scientists and also a well-known vertebrate model species widely used in research. Zebrafish, are also a popular species among aquarists and have been put in aquariums all around the world as ornamental fish. The acid rain phenomenon has lowered the pH level of the wild habitat of zebrafish by shifting it to a more acidic pH level. This study was carried out to observe the effect of low pH level on the reproductive performance of zebrafish. The zebrafish were quarantined for a week to make sure they were healthy to be used in the experiment. The zebrafish were reared continuously for 14 days in three different pH treatments T1 (pH 2-4), T2 (pH 4-6), T3 (pH 6-8)). T3 (pH 6-8) was used as the control treatment. Hydrochloric acid (HCl) was used to control the pH level of treatments T1 (pH 2-4), T2 (pH 4-6), T3 (pH 6-8) with three replicates of each treatment. The male chasing female frequency was significant (p: 0.0001) and the data showed the highest frequency (2568.000±140.6272) at treatment 3 (pH 6-8). For the spawning frequency of zebrafish, treatment 3 (pH 6-8) showed the highest value (4.000±0.5774) followed by treatment 2 and treatment 1 and the data was significant (p: 0.0004). The fertilisation rate of the zebrafish was significant (p: 0.0001) and the highest was shown at T2 (pH 4-6) with 89.8018±0.3782, followed by T3 and treatment T1. For the hatching rate of the zebrafish, the data collected were significant (p: 0.0002) and the highest value of 2.9350±0.4070 was shown at T3 (pH 6-8), followed by T2 (pH 4-6) and T1 (pH 2-4). The overall result showed that pH 2-4 had the worst effect on the reproductive performance of zebrafish. Therefore, low pH has a significant effect on reducing the reproductive performance of zebrafish. The local fish population can be affected by the decrease of pH level due to acid rains and chemical waste pollution.