V.C. Mwambazi (Ms)
Department of Fisheries
Fisheries Research Division
P.O. Box 350100
This paper is a general review of post-harvest fish technology trends in Zambia. The importance of fish in the country and existing methods of its handling, processing, storage and distribution are outlined. Post-harvest losses of cured fish are briefly discussed. Extracts on what has been done and so far carried out on the improvement in handling and processing of fish in Zambia are outlined.
Le document passe en revue le les tendances générales dans la technologie du poisson après la capture. L'importance du poisson dans le régime alimentaire en Zambie y est soulignée, et les méthodes de manutention, transformation, stockage et distribution y sont décrites. Les pertes après la capture sont examinées brièvement. De brèves information sont également données sur les activités menées jusqu'à présent dans le domaine de la conservation et de la transformation du poisson.
Zambia, being a landlocked country, derives all its fish from inland waters which are in the form of lakes, rivers, dams and fish ponds. The fisheries are located far from urban areas where most of the fish marketing takes place. This means that the greater part of the fish marketed in urban areas is not fresh but processed in one form or the other. The prevention of post-harvest losses is important at various stages of the fish marketing chain.
Most fish landed in Zambia is caught overnight by artisanal fishing through gill netting and seine-netting. The gillnets are set before dusk and hauled in during the early morning hours. The time that the nets are in the water ranges from 11 to 14 hours. Research surveys in the Kariba area show that an average of about 35% by weight of the total catch of Hydrocynus vittatus spoils due to bacterial attack and autolysis if nets are set for more than 13 hours (Fig 1). Percentage spoilage was calculated as the total weight of fish found rotten or showing signs of spoilage through general appearance over the total weight of catch from a particular haul as shown below:
The results were obtained from loss assessment surveys made between April 1986 and April 1990.
2. TRADITIONAL METHODS OF HANDLING FRESH FISH
Traditional methods of handling fish do not include gutting or the use of ice and as a result the quality of fresh fish suffers greatly before it can be processed. Fishing is done mostly at night by artisanal fishermen.
Fig 1. Relationship between fresh spoilage and time after death at ambient temperature
The fishing ground can be as near as 30 m from the harbour but many kilometres may be covered by fishermen using dugout canoes during their fishing exercise.
There are no proper containers on the boat for collecting fish during the fishing exercise and as no ice is used, aquatic weed is used as a cover to protect the fish from the tropical heat. Even among commercial fishing companies like those active on Lake Kariba, very few if any have adopted the use of ice or chilled water and consequently the quality of kapenta is usually very poor. Bacterial contamination on the fish is high because of these unhygienic handling methods. The reasons why the use of ice is uncommon among fishermen in Zambia are wide and varied:
Lack of ice plants near fishing areas.
Cost of the commodity (ice) is very high.
Due to the warm environment ice melts quickly and is lost before it can achieve the desired results for which it is intended.
Fresh fish is sold whole and ungutted, directly from the boat at the harbour. The majority of fish traders are women marketeers who use anything, from metal buckets to dishes as containers for carrying fish from the harbour to the markets. Some marketeers wash the fish before packing but the water at the harbour is rarely clean. A little crushed ice may be sparingly sprinkled on top of the fish in the container and then covered with a sack to temporarily preserve the ice both during transportation and before marketing of fish. When available sawdust can be used as the best insulation material for keeping the ice intact for a long time. In most cases only water weeds are used to keep the fish fresh in the absence of ice.
The mode of transporting fresh fish is either by open vans or lorries for distances of not more than 100 km. For longer distances, e.g., from Luapula Province to Lusaka, insulated boxes are used. Most fresh fish is retailed in urban markets. The larger markets like Kamwala in Lusaka, have sheds with concrete stalls, running water and drains. Smaller markets have makeshift wooden stalls, but lack running water and have poor drainage facilities. The fish being sold is kept in iced containers. And during sales, the product is vulnerable to blowfly attack and dust. The fish is washed or sprinkled with water from time to time to remove dust, slime and to keep away flies. At times fish is covered by a wet sack cloth to prevent both flies and dust from settling on it.
2.1 Dried Fish Handling
Because of the scarcity of ice and the cost involved in procuring it, about 80% of fish caught in Zambia is traditionally processed by drying. Some of the factors which make dry processing of fish a popular method are:
the product can be stored for up to nine months before it is marketed;
poor transport network makes it difficult for fish to be transported in its fresh form;
consumer preferences: many Zambians prefer to eat fish which is processed by drying, salting or smoking, since this is part of their culinary tradition.
3. TRADITIONAL METHODS OF SUN-DRYING FISH
The most popular traditional method of processing fish in Zambia is sun-drying with mild smoking depending on the size and species of the fish and also on the fishery. Most fish are dried on wooden boards and reeds and grass mats which are laid on the ground (giving no protection from rodents, ants, insects, chickens and probably dogs). Since the fish is laid on the ground, water accumulates around it instead of draining away. Traditional drying process offers no protection to the product from rain and high humid environment (Fig. 2b). A 10% contamination of sand, grit and dirt has been recorded due to the above drying methods.
Chisense from Lakes Mweru/Luapula, Mweru-wa-Ntipa and Bangweulu are dried in a similar manner. However, kapenta (sardine) from Lake Tanganyika is dried on concrete slabs or cemented floors which are used as an improved alternative. Fig 2a illustrates an improved drying rack.
|Fig. 2a. Fish drying rack|
The inadequacy of drying the fish makes it susceptible to blowflies, mould and beetle attack. As a result, fishermen and fish traders have resorted to insecticides in order to reduce losses. A gas chromotograph analysis carried out on dried fish samples obtained from fish traders operating around Siavonga on Lake Kariba showed a content of about 0.224 ppm of Deltametrin. Since no maximum residue limits have been set internationally for most of the insecticides on cured fish, emphasis should be on better drying methods to prevent the use of insecticides as a way of prolonging the shelflife of cured fish. In Zambia the use of insecticides as a means of preventing post-harvest fish losses is banned although some fishermen and fish traders use them illegally.
Almost all cichlids in Mweru-wa-Ntipa of medium size are scaled, gutted and cleaned but not split. They are sun-dried for about 20 min to remove surface moisture and then smoked for 2–3 days.
In swampy areas like Lukanga and Bangweulu smoking is difficult due to lack of wood fuel. Fishermen have to buy wood and transport it long distances across the swamps in dugout canoes.
The use of salt for curing fish is not widespread in Zambia since salt is an expensive commodity in the country and not readily available in some areas. Because of this, fishermen are reluctant to use brine although research has shown that salt has the following effects on fish:
it improves the quality of the product;
it achieves longer storage life and improves texture of the cured fish;
it inhibits microbial and mould growth;
it reduces fragmentation;
it reduces losses from insect attack by more than 50% and the shelflife is longer.
Fig. 2b. Traditional drying versus drying racks
|Traditional drying||Drying racks|
Traditional dry salting techniques are used extensively around Lakes Mweru and Mweru-wa-Ntipa. This is so because cheap salt is found around the area (Mweru-wa-Ntipa). The local residents have devised a technique of processing salt which is later sold to fishermen or fish traders.
Hot smoking is another popular traditional method of processing fish in Zambia. The fish is smoked on pits or raised smoking racks where the control of heat is difficult. The fish thus processed results into an overdried, brittle and irregularly shaped product. Wet weather is also a constraint when processing as most of the traditional processing methods offer no protection to the product and the processor from the rain. Smoke densities and temperatures are very crudely controlled by regulating the fire and the process requires a high degree of supervision by an experienced operator. Apart from drying, hot smoking partially cooks the product and also imparts a smoky flavour.
Investigation on fish processed by fishermen show that about 10% or more of fish losses are due to fragmentation.
As a means of preserving fish, traditional methods have certain technical limitations. Very fatty fish may not dry satisfactorily and in wet weather fish drying may not be possible at all.
4. TRADITIONAL PRACTICES OF HANDLING, STORING AND DISTRIBUTING CURED FISH
The storage period of fish in Zambia is short due to a high demand for the commodity. However, a fish trader often spends 6–8 weeks in a fishing camp buying fish before it can be transported to the markets (peri-urban and urban).
Research findings have shown that beetle attack can start as early as the first week of storage. Watanabe and Cabrita (1971) estimated that 10% of the processed fish produced is spoiled due to beetle infestation. Packaging techniques in Zambia offer very little protection to the dried product from fragmentation. Often the dried fish is wrapped in a bundle. This can be made either from reeds or grass and at times brown paper mainly from empty cement bags. It is tied with flexible sticks and fibre which act as a frame. The bundles are then transported by road from the camps to the markets where they are sold. The fish is either sold in bundles or in small heaps depending on the size of the fish.
5. IMPROVED PROCESSING METHODS
The introduction and construction of raised fish drying racks during sun-drying has brought the following advantages:
it protects fish from being eaten by animals like dogs, cats and some insects;
there is less contamination from dirt and dust;
drainage of water from the wet fish is facilitated;
air currents or winds can pass both above and underneath the fish hence effecting a quick and efficient drying process;
during wet weather fish can be protected from rain and ground water by covering with a sheet of plastic or any other waterproof material. The use of drying racks has become popular among the kapenta commercial fishermen along Lake Kariba. Fig. 2b illustrates the difference between traditional and raised drying racks.
5.2 Improved Smoking Processes.
Various research findings and recommendations have been made in Zambia on improved processing techniques. Watanabe and Joeries (1967) proposed a drum-smoker for processing the catch of an individual fisherman. This design had one or two advantages over the traditional open-pit method of hot smoking used throughout Zambia. It is much easier to regulate temperature and smoke concentration inside the kiln. The product produced is less brittle and has an attractive yellowish-brown colour if the right smoke density is applied. One of the disadvantages of the drum smoker was its limited capacity; very little fish can be processed at a time.
Watanabe and Cabrita (1971) proposed a smoking kiln for a medium or large scale smoking operation under rural conditions.
Clucas (1976) recommended the mud and pole type of a smoking kiln which was easier and cheap to construct.
The Chorkor fish smoker proved to be the most appropriate technology for fish smoking for the Zambian environment. This was a recommendation of the FAO Expert Consultation on Fish Technology in Africa (1985). Materials for the construction of the Chorkor smoker can be obtained locally and cheaply.
Fig 3. Chorkor oven with tray (up to 15 trays can be stacked)
5.3 Improved Storage Facility
Cured fish is usually stored at the processing site, at intermediate collecting centres and at the point of marketing and distribution. There are various reasons for storage, some of which include the need to accumulate an economic load for transport, evening out seasonal variations in supply, waiting to find buyer/transport and commercial strategy. The duration of storage at each point in the chain varies substantially. Although the storage period of processed fish is short in Zambia, severe damage on the fish still occurs due to bad storage facilities.
A good storage facility should provide:
security, appropriate to the location;
a roof to shade the stored fish, to keep off rain and reduce any possible overnight formation of dew on fish;
protection from groundwater, either by raising the product above the ground or by providing a floor incorporating a water vapour barrier.
In Zambia much needs to be done to reduce the high percentage of post-harvest losses. Not only is the product poor in quality but also reduced in quantity. Wastage begins from the time the fish is caught, and continues as it is processed, packaged, transported and stored.
Research in fish processing has had very little impact in improving traditional processing practices in the fishing industry. Some of these problems have already been outlined. There are few data available to show the reasons why improved smoking kilns which were initiated by researchers like Watanabe and Joeris have not yet been adopted by fishermen or fish traders; reasons include the following:
The drum smoker, proposed by Watanabe and Joeris (1967) was of limited capacity, restricting the quantity of fish processed at a time.
Fishermen preferred using the drum for brewing beer and other purposes to smoking fish.
Artisanal fishermen are highly nomadic people going where the catches are high, hence they did not like structures such as proposed by Clucas (1976).
Costs and other restraining factors like permanent clean water supply, has made building good smoking kilns like the one designed by Watanabe and Cabrita (1971) an unattractive venture to both fishermen and fish traders.
Extension services are probably not adequate.
Lastly, there are no incentives given to fishermen, traders and marketeers for improved quality of their product. The fish is sold regardless of the quality.
The Prevention of Losses in Cured Fish. FAO Fish.Tech.Pap., (219)
Fish Processing in Africa. FAO Fish.Rep. (329)
Clucas, I.J. 1976. Present fish drying techniques in Zambia and suggested improvement.
Lawson, R. 1984. Economics of Fisheries Development
Watanabe and Cabrita. 1971. Salted and smoked fish
Watanabe and Joeries. 1976. How to smoke fish in a drum-smoker