DefinePK

Abstract

A local fish farmer experienced high mortality rate of fishes from his fish pond located in a city of Port Harcourt, Nigeria. In order to ascertain the cause of the death of these fishes, some selected physicochemical and microbiological parameters were used to determine the concentration which resulted in lethal effect on the fishes. Test results indicated that among the parameters determined, the concentration of ammonia in both the storage tank and aquarium exceeded the maximum limit of 0.2mg/l for aquatic life. The ammonia concentrations from test results ranged from 0.25mg/l to 0.50mg/l. The sample with 0.50mg/l also indicated the highest level of total coliform of 3.52 x 103(cfu/100ml) as against the sample with 0.25mg/l with Total Coliform of 0.0 (cfu/100ml). Moreover, higher values of pH (7.45), TDS (104mg/l), Electrical conductivity (208µScm-1), Chloride (75.76mg/l), Nitrate (2.00mg/l), Calcium (0.94mg/l) respectively were seen in the sample with the highest level of ammonia (0.5mg/l). The death of the fishes was more evident with the sample having 0.5mg/l, followed by the sample with 0.35mg/l of ammonia.  Test result therefore confirms that ammonia concentration of above 0.20mg/l in fish ponds has a tendency to harm the fishes.