Bringing an existing fish production demonstration unit into operation and the planned establishment of a national aquaculture diagnostic laboratory are positive developments that will improve fish health and boost farm productivity, says the Fish Producers’ Association of Zimbabwe.
The aquaculture diagnostic lab will be housed at the Veterinary Research Laboratory, which is presently the national livestock diagnostic testing centre of the Department of Veterinary Services. The fish production demonstration unit is located at the Henderson Research Institute in Mazowe, about 40 km north-west of the capital Harare.
In a statement, the association said since fish-focused research is part of the mandate of the demonstration unit at the Henderson Research Institute, its reactivation could help boost fish health by providing testing for aquatic environmental health and fish diseases.
“Successful commercial fish production starts with the sourcing of healthy fingerlings from environmentally clean and disease-free stocks. Biosecurity should be practiced to ensure that fish diseases are not introduced into a fish project from another source.
“Maintaining the aquatic environment in a condition that will not compromise fish health or precipitate disease is also critical, as it is difficult to isolate diseased fish to avoid contamination, which can easily spread in an aquatic environment,” the association said.
For optimum health and performance, fish farmers were advised to meet the nutritional requirements of growing fish, while ensuring that they are not subjected to stress.
AQUACULTURE CODE OF PRACTICE
Fish health lies at the core of the new draft code of practice for aquaculture spearheaded by the association. The code forms the national best practices aquaculture guideline for the production, processing, health, hygiene, as well as environmental and food safety of fish.
“The code recognises the Department of Veterinary Services as the national authority in fish disease surveillance and control, and emphasises the importance of environmental stewardship in sustainable commercial fish production.
“The importance of good aquaculture practices can be seen when it is realised most bacterial diseases in fish are secondary infections that occur in fish that are under stress from poor water quality, ectoparasites or poor nutrition,” the producers said.
DISEASES THREATEN FISH FARMING
Presently, aquaculture in Zimbabwe is threatened by bacterial diseases that include Streptococcus iniae and Flavobacterium, which are blamed for causing mass mortalities on fish farms. However, the association said the two fungal diseases that affect national fish production can be easily prevented.
“To avoid Saprolegnia, which is a waste or sewage water-borne disease, wastes should never be emptied into fish ponds. Aspergillus can develop in mouldy feeds, so only fresh feed should be fed to fish. Like all other livestock, fish can be infected with parasites. Some of those are detrimental to fish health and are transmissible to humans.
“However, the risk of aquatic parasites can be minimised with biosecurity measures. These include disinfecting equipment, monitoring of water quality and disease, general sanitation of the aquaculture facility, and use of protective wear by personnel working at the operation,” the association advised.
Some indications of disease in fish include stunted growth, unresponsiveness to external stimuli, lack of interest in feeding, breathing difficulties, and lesions on the skin. Other symptoms include uncharacteristic behaviours such as gasping, lethargic swimming, spinning and sudden deaths.
Among other high mortality fish diseases, Zimbabwe is also monitoring the emergence of the Tilapia Lake Virus and working to contain a spreading outbreak of the epizootic ulcerative syndrome, which has been confirmed in 25 bodies of water across the country.