WILDLIFE MANAGEMENT- WARM WATER FISH FARMING
Warmwater fish farming in KwaZulu-Natal
T. Pike
The possible aims of fish farming include the production of fish for domestic consumption or as staff rations, the sale of fresh or processed fish on the open market, the sale of fry for aquaculture or angling purposes, or the provision of personal or rented angling.  

 
These aims could be met by merely cropping the natural production of existing impoundments or by semi-intensive production involving precise management.
Intensive fish farming is costly and requires careful management.
Therefore, before embarking on a full-scale project it is advisable to run a pilot scheme to judge the feasibility of, and market for, a larger operation.
Water

Water is the most critical factor in a fish farming development. The source of water could be a spring or borehole, local surface runoff, a stream or river, a dam, or even heated power station effluent. A flow of 100 litres per minute could support 0,28 ha of fishponds that are 0,5 to 1m deep. A minimum flow of 1700 litres per minute during the growing season is needed to support the smallest commercially viable fish farm comprising 5ha of ponds. If the water supply is limited it can be supplemented by being recycled through a biological filter. Temperature affects growth, thus the number of days per year that the water temperature does not drop below 15° C constitutes the growing season. The ideal range for growth is 15 - 34°C. Water temperatures above 36°C or below 8°C, or a sudden drop of 4° can kill most species of warmwater fish.

Silting or pollution renders the water supply less suitable for fish farming. Possible pollutants include cattle dip, insecticides, herbicides, industrial and sewage effluent, soaps, detergents or petroleum and its by-products.

The site
An altitude of 500m above sea level is about the maximum acceptable for efficient warmwater fish farming. The farm should be located fairly near to its potential market so as to limit transport costs. Good road access to the site itself is essential. There should be no danger of flooding by either river or surface runoff. A ground slope of 1:20 is ideal. This facilitates water gravitation and pond drainage. Ponds built on level ground are difficult to drain, and it is expensive to build ponds on steep slopes. A frost-free north facing aspect sheltered from any cold prevailing winds, is preferable. Although light frosts are tolerable, heavy frosting inhibits fish growth, and can be lethal. Loamy soil with a moderate clay content is ideal for pond construction, whereas sand, shale and rocky soil necessitate sealing and may be expensive to excavate.

Layout and ponds
Water supply, preferably by gravity feed, and pond layout should be designed according to terrain, using the contours. Reticulated water supply and drainage lines, comprising furrows or pipes should be interconnected but each pond should be able to be isolated if necessary for maintenance purposes or to prevent the spread of disease. Hatchery, office and storeroom buildings should be located adjacent to the area developed for ponds.

Fish can be reared in farm dams, earth or concrete ponds, or in portable plastic pools. Fishponds should have sloping sides and it should be possible to drain them completely. Ideally, the water depth should be from 0,5 to1m. Fish can also be reared in floating or fixed cages placed in a dam. The ponds should be protected against fish predators (birds, otters, platannas) and be safeguarded against human interference and theft.

Management
Fertilizing the water with organic or inorganic fertilizers helps to stimulate the production of natural food organisms. Supplementary feeds such as grass cuttings. Kitchen vegetable and grain waste or commercially available pellets may be provided, depending on the species of fish being cultured. Aeration of the water enhances fish growth. Aeration is essential if the ammonia or oxygen level becomes critical, which may be caused by overstocking, over fertilization, excessive waterweeds or algae, high water temperature, or extreme humidity. Aeration of the soil by the periodic drying out of the ponds and the addition of lime also enhances production. The levels of dissolved oxygen, pH and ammonia need to be monitored to prevent them reaching unproductive or lethal limits.

Equipment
The scale and type of the fish farming operation will govern the type and quantity of equipment. Large dragnets, with mesh sizes suited to the size of fish to be caught, as well as long- and short- handled nets are essential. Other equipment needed includes accurate scales, measuring boards, thermometers, water testing apparatus, incubation funnels, troughs and gauze trays for sorting and rearing fry, water tanks, buckets and drums for holding and transporting fish.

Disease
If hygienic conditions are maintained and if overstocking or nutritional deficiencies do not occur, most diseases and infections will be prevented. The commonest fish diseases include malnutrition ailments, and parasite or skin infections, which can be treated by the farmers. Overstocking increases the likelihood of disease breaking out, and pathogens can be transmitted by water passing from pond to pond, therefore infected ponds need to be isolated. Assistance in disease diagnosis and advice on controls are available from Allerton and Onderstepoort veterinary laboratories, the KwaZulu-Natal Nature Conservation Service, and from various universities.

Suitable species
The following fish species are recommended for warmwater fish farming:
Mozambique tilapia Oreochromis mossambicus
Redbreast tilapia, Tilapia rendalli
Sharptooth catfish, Clarias fariepinus (barbel)
Common carp, cyprinis carpio
Grass carp, Cyprinus idella
Silver carp, Hypophthalmichthys molitrix
Largemouth black bass, Micropterus salmoides
Fish importation or the collections of stocks from the wild are subject to control by permit from the KZN Nature Conservation Service.

Breeding and production
All of the fishes listed in the previous section are summer spawners. Spawning can be allowed to take place naturally when the fish mature in spring or can be aided by providing suitable nesting materials. Spawning of some species may also be induced by hormone injection or by water level manipulation. Eggs and milt can be manually stripped from the fish, and the fertilized ova artificially incubated. Mass-production of fry of some species can be achieved by removing the fry at an early stage for artificial rearing. The breeding season can be extended by means of light and temperature control.

Fish can be cultured as single or multi-species populations and as single sex (one sex only) or mixed sex populations. Polyculture using several compatible species together can maximize the use of all the natural food types and pond space available.

Production can be improved by means of strain selection, single sex culture, which saves energy loss through spawning, or by combining fish culture with the use of byproducts from duck, pig, or market garden farming.

Fish stocking densities should be regulated to maximize growth and to prevent stunting by overcrowding. For best growth the fish should be graded by size so that each pond contains fish of more or less uniform size.

Marketing
Fish may be sold on-site at urban outlets, alive or freshly slaughtered, whole or dressed. Fish to be sold alive must be transported in aerated water. After slaughtering, fish should be gilled and gutted immediately so as to prevent deterioration, but should be scaled only at the point of sale so as to prevent unnecessary drying out. Slaughtered fish can be sold filleted, dried, smoked or canned.

Fish sold for consumption should be attractively packed and presented. Production should be geared to market demand. Refrigerated storage could facilitate the provision of steady supplies to the market. Marketing strategy depends on the producer’s fish farming objective. Local market research is essential to determine the economic viability of the project. The developer needs to undertake his or her own market research and advertising, since little is yet known about these aspects in KwaZulu-Natal.

NB: The preparation and preservation of fish is subject to health regulations. Failure to comply with requirements could result in closure of the operation.

Economics
Capital costs will include land purchase, roads, buildings, water system construction, and the purchase of specialized equipment and vehicles. Running costs include the provision of fish feeds, fertilizer, power, staff salaries and clothing, expendable equipment and medications, as well as transport costs and vehicle maintenance. Feed costs can be reduced if waste from ducks, pigs, or from the food industry are available.

The fish farmer should assess the potential sale price of his product, as well as the cost/benefit balance for himself. Potential prices of some fish are R2 to R3 per kg for dressed tilapia, carp or catfish, and R7 per Kg for catfish fillets. Processed fish such as filleted, smoked or canned fish should fetch higher prices than dressed fish. Additional income can be obtained from the sale of ducks and pigs reared on a multi-purpose project.

Legal aspects
The water act 54 of 1956 as amended, regulates the abstracting of water in excess of a volume of 100 Litres/second from any source, and the quality of the effluent water returned. The Nature Conservation Ordinance 15 of 1974 regulates the establishment and operation of fish farms. A fish-farming permit is required, and the importation of fish and their introduction into KwaZulu- Natal waters are also subject to a permit. The introduction of alien freshwater organisms into KwaZulu-Natal is prohibited because of the danger of undesirable crossbreeding and genetic pollution, or competition with indigenous species. The Health Act 63 of 1977 and the Foodstuffs Act 54 of 1972 regulate the handling and abattoir requirements for saleable foodstuffs. The Standards Act 33 of 1962 regulates the standard of products sold for consumption.

The development and operation of a fish farming enterprise remains the responsibility of the individual, although various authorities can provide advice. No guarantee is made that a given development will be financially viable.

Information
Further information on aspects of fish farming is available from the KwaZulu-Natal Nature Conservation Service, P O Box 13053 Cascades 3202.

Acknowledgments
I express my gratitude to Mark Sasman, Mike Coke, and Terry Ferguson who contributed to the production of the original manuscript.

KEY POINTS
A reliable, clean water supply and frost-free climate are essential.
Research the market and economics before starting.
Start with a small pilot scheme.
Good production depends largely on careful design and good management.