WATER QUALITY MANAGEMENT FOR CATFISH HATCHERIES
The success of every fish hatchery depends largely on the quality of water available for its fish breeding processes. Hatching fish eggs entails providing suitable environment (mainly water), for hitch free incubation of eggs and eventual development of hatchlings (fry) to attain life stages that command market value.
Man’s primary purpose for artificial breeding of fish is to augment natural reproduction of fish in the wild, which over the years has lagged behind the rate at which fish populations are demanded for human consumption.
A worthwhile fish hatchery venture must thus be efficient enough to profitably yield fish seed (fingerlings) in reasonable and consistent number.
To achieve the aforementioned, availability of abundant water of optimum quality is non-negotiable. Water quality for a fish hatchery is assessed in two broad sets of characteristics. These are;
- Physicochemical characteristics / parameters
- Biological Parameters
The following are physicochemical parameters to look out for, and ensure their optimum levels in water designated for fish hatching purpose, recorded alongside their corresponding optimum limits.
Temperature at 25° – 30° Celsius
Dissolved Oxygen at >/= 5 ppm (parts per million)
Carbon IV Oxide at <12ppm
pH at 6.5 – 8.0
Ca2+ (Calcium Hardness) at >20ppm
Mg2+ (Magnesium Hardness) at 20 – 100ppm
Total Hardness at 60 – 150ppm
Salinity at 500 – 1,000ppm
NO2- (Nitrite) at <0.05ppm
NO3- (Nitrate) at <250ppm
Fe2+ (Iron) at <0.6ppm
NH4+ (Ammonium) at <8pp
Nitrogen at <100% Saturation
It is a wise decision for every hatchery to seek to identify what values each of these parameters measure in their source water. A lot of effort in futility goes to running a hatchery blindly (without an analysis of the water that runs it).
Evaluating a source water sample and taking measures to correct parameters that measure values outside the optimum limits had helped resuscitate many hitherto unproductive fish hatcheries. A number of measures can be applied to correct water quality parameters that happen to fall outside optimum limits. These will be discussed under subsequent headings.
Because water designated for fish hatching purpose is normally first identified physically as free of unwanted materials, the main biological Parameters of concern are usually microbial in nature.
A given clear looking water could habour dense populations of microorganisms that are capable of hindering successful fish hatching. Biological matter that could be present and of concern in water for fish hatcheries include;
Each of these could be present in water in a wide variety of strains, from the safe and beneficial, to the parasitic and very harmful ones.
Water for fish hatching can be almost completely rid of harmful biological matter by employing the use of Ultra Violet lighting devices.
A number of antimicrobial chemicals are also used (with expert handling) to wipe out populations of harmful microorganisms in fish hatcheries, while causing no harm to fragile fish hatchlings.