Evaluating water quality: a case study of two fish hatcheries in distress

Abstract

Some fish hatcheries situated at the Lekki stretch of Lagos State have recently experienced repeated production failures. Successful management of fish hatcheries to meet production goals assumes that the quality of the water used to fill the incubation and nursery tanks is consistently high. Analysis of water from two privately owned hatcheries located at Lakowe indicated water quality that is outside the acceptable range. Sources of the water quality problems varied between the hatcheries, but include poor exchange, and daily additions of nutrient-rich feed which exacerbates existing water quality problems if no exchange is carried out routinely. Complaints of total fish kills at days 3 to 5 of age had been presented by the hatchery owners. Extreme water parameter values were observed after an assessment of the water collected from the two hatcheries. Farm I showed low pH values that ranged from 4.5 – 6.5 while for Farm II it was 6.5 – 7.2. Lethal levels of phosphate and ammonia were obtained for Farm II which ranged from 0.5 – 10 mg/L and 1.5 – 8 mg/L respectively, however the phosphate and ammonia levels for Farm I were 0 mg/L and 0 – 1 mg/L respectively. Nitrite levels for both hatcheries were satisfactory at 0 mg/L. Poor water quality has a deleterious impact on fry survival and result in huge economic losses for a hatchery operator. This paper attempts to present the outcome of the water chemistry from the case studies and juxtapose them with water parameters from a fish hatchery in a research institute where successful breeding cycles have been obtained.