Zimbabwe's Nyanga National Park has a unique trout hatchery, where the June/July winter weather conditions of the mountainous area are ideal for rearing the fish. Trout fishing in the park is a sport for both tourists and locals.
Matthew Gambe, in charge of the hatchery in the park's laboratory, explained the production rocess. "Trout is an exotic fish introduced here from South America and Scotland. It does not do n a natural system. It was tried and failed in the Odzi River because of the unsuitable weather onditions. But these fish can be farmed in cold weather and the high elevation of Nyanga National Park became the ideal home for the farming of trout. Water of over 23 degrees Celsius temperature is dangerous to the trout, which develop a fungal disease. "
"We established two types, the rainbow and the brown trout. The rainbow responded to the conditions positively and survived; the brown struggled and died because it required deeper waters," he said. These are carnivorous fish; they feed on pellets and insects and worms. When fully grown from a good breed, the fish weighs between 500grammes and a kilogramme.
“The hatchery is the centrepiece for the mass production of trout. Everything is controlled, especially temperatures. Breeding is done in winter, especially in the coldest months of June and July and rarely in August. In winter, we take each of the trout for testing, which involves squeezing eggs from the female and sperm from the male. This is carried out under carefully controlled light in the a hatchery and the eggs are collected in special plastic containers, " said Gambe.
The eggs are measured and the ideal volume of good eggs is about 300ml. Trout fish differ in size and this affects the quality of both the eggs and the sperms. Breeding takes this into consideration. The bigger the eggs, the bigger the breed. Also, the bigger the egg, the bigger the female. The breed stock are collected. Those that fail to meet the grade are taken back to the waters; their eggs are not used for fertilisation. The trout offspring from the hatchery are placed in so-called quality dams, where fishing is permitted.
"We normally breed thousands of trout in the hatchery in a single sitting in June and July, but this depends on orders from the market," said Gambe. "Trout farmers around us have no hatchery and we get orders from them before the farming season begins in winter. But we do not just sell the trout to anyone; we consider the farmer's location as this has implications on temperatures,” he said.
When trout are infested with fungus, the water bubbles. This is an indication that something is wrong. The trout would have developed wounds and the quality of the water again has to be assessed consistently. Natural waters, far from being clean, are disease niches and only fully-grown trout can resist their hostility. We sometimes clean the ponds after every fortnight. For quality dams in which quality trout live, cleaning is done every day," said Gambe. The strict breeding requirements are one reason why growing trout is expensive.
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