Fish farming is the way of the future

ONALENNA MODIKWA
Staff Writer | Friday June 11, 2010 00:00

It is either because aspiring farmers know little about fish farming or they are not aware that it is another sector that can be explored especially because greater opportunities are available in it than in any other agricultural sector.

Even the majority of people around Mmadinare area are not aware of the existence of the fish hatchery, the biggest or possibly the only one in Botswana.  It lies in an isolated place past Letsibogo Dam. There is not much activity by people touring the place like one would expect in a national facility like this hatchery, yet officials are there to teach them about fish farming.

Assistant scientific officer in the Department of Wildlife and National Parks, John Choto, says 90 percent of their clients are willing to engage in commercial fish farming, however, they are delayed by the lengthy processes of securing funds.  Only 10 percent of the hatchery's clients are subsistence farmers. 'We want commercial fish farmers to come forward for assistance because fish farming has not been fully utilised in the country.

People should know that this sector is still open and this facility can produce sufficient supply of fish affordably. 'A single fish costs only 50 thebe. To venture into fish farming, simply requires the availability of adequate water supply and enough land to cater for ponds, storage facilities and offices.  'Currently, no permits are required to own a fish farm but before embarking in this business the prospective farmer has to request for site assessment from our department and to gather enough information on the nature of the business'.  The fish hatchery's major objective is to produce fish up to a finger size for sale to prospective fish farmers and for stocking in community dams and Water Utilities Corporation dams. It also acts as a demonstration and education centre on fish farming to different user groups such as students, institutions, organisation and prospective farmers and individuals. 'We do encourage fish farmers to do market research first lest they run unprofitably with overpopulation of fish,' says the farm spokesperson.

The fish hatchery cultures only two fish species being the catfish and the bream due to the fact that they are good commercial aquaculture species in Southern African conditions. 'They were selected considering that they are able to reproduce in captivity, simple culture for the young ones, growth rate, market demand, food preference and disease resistance'.The catfish do not usually reproduce in captivity when kept in small ponds so Choto indicates that they inject them with hormones that triggers them to start laying eggs.  This fish lays up to one hundred thousand eggs once or twice in a year. The eggs are laid in water and left to hatch on their own and this normally takes 24 hours.

He indicates that normally less percentages of eggs hatch due to natural environmental constraints. This fish species is a carnivore and may feed on the bream species if they are stocked together. As a result, the species are kept separately with the aggressive catfish having to be kept a reasonable distance from others as it can spring out and feed on them. The catfish has the ability to grow well when stocked in large numbers in a small area.

They can gain and reach market size within a period of six months. With the breams, they lay eggs in water and the male fertilises the eggs externally. The female takes up the eggs in her mouth to protect them from the environment and predators.  The mouth also acts as an incubator until they hatch and delivered in a safe place. This species is able to reproduce in captivity when conditions are favourable and they can breed every month.

This normally creates a population problem in small ponds for commercial fish farmers. When collecting eggs from the breams in the hatchery officials open the mouths of female fish and flush eggs out and place them in an incubator. 'It has been scientifically proved that male breams grow big and fast in a short period of time when compared to the females who use most of their energy for reproduction while males use their energy for muscle gains,' says the fish farmer.

The stock in the hatchery is sourced from Letsibogo dam and taken to the ponds at the hatchery. They are kept there for sometime to monitor them for diseases and other possible effects that they may bring to the fish already in the hatchery. They are then taken into culture tanks so that they can mate and act as a source of eggs in the hatchery. Choto noted that in a case of commercial fish farming only males are wanted because they grow fast and gain weight fast in a short period of time. 'Males also help in stocking density management since the farmer do not have to worry about high population which results in competition for space, food and oxygen resulting in stunted growth and extended periods of reaching market weight leading to a commercial loss'.

He further indicated that for a farmer to make a profitable business from the bream species since it is the widely accepted fish in the market the only solution is to identify males and females and separate them and raise males alone. Mmadinare fish hatchery produces monosex bream fingerlings for supply to prospective fish farmers. The hatchery converts most fish fingerlings that are to be sold to commercial farmers into males so that farmers do not have to worry about stocking density.

The process is called sex reversal and it is achieved by feeding the fish with hormone treated feeds that help suppress the development of female gonads so that all fish become male and behave like males. 'The hormone has no side effects to the fish, to the environment and even to the consumer. The hormone treated feeds are fed for 30 days from hatching eight times a day at two hours intervals.

'After a month of feeding we then check to see if they have all changed their sexes. They are then fed starters until they are ready to be sold to prospective fish farmers. The infrastructure in the hatchery is the hatchery building and the outside pond. The purpose of the hatchery building is to produce the fingerlings. This is where the eggs are collected and incubated then after hatching the newly hatched fish are fed until they reach the finger size. Oxygen is supplied and the temperature is controlled and fish rely only on artificial feeds. Due to these artificial supplements the hatchery can produce a large number of fish in a small area.  The outside ponds, on the other hand, are used to house fish. The fish in the ponds depend on the natural environment from oxygen supply and for temperature regulation.  They may also rely on natural food production, which includes microscopic organisms. The water in the pond is not treated so the number of fish has to be regulated in order to reduce pollution. Under good management the pond system may prove to be the cheapest method of raising fish.