The effect of pH and conductivity on the electric behaviour of Apteronotus albifrons (family Apteronotidae) in a pollution monitoring system

The Electric Organ Discharge (EOD) frequency and waveform of the neotropical fish, Apteronotus albifrons (Gymnotiformes) are used to monitor water quality. This study evaluates the effects of two environmental variables, pH and water conductivity on the fish's electric behaviour. Variation in pH is shown to have no effect on the EOD waveform. On the other hand, the EOD frequency decreases significantly under acidic conditions (down to pH 3.6) and increases as the pH rises (to 10.6). A closer examination shows that the most satisfactory mathematical model for describing the pH frequency variation is a three degree polynomial. For narrow pH intervals, EOD frequency and pH are shown to be linearly related with significant increases in the discharge rate taking place on the two pH intervals: 5 to 7.6 (Student t-test value ≥23.47; degree of freedom = 48; probability < 0.001) and 9.2 to 10.5 (Student t-test value ≥6.186; degree of freedom = 48; probability < 0.001). It is also possible to show that the EOD freq...