Tilapia has been farmed in ponds for thousands of years, and the Ancient Egyptians are for instance known to have raised Nile tilapia in ponds along the river Nile. During the 1950s an important step in the history of farmed tilapia was taken when Tel Aviv University zoologist Prof. Lev Fishelson developed a hybrid of tilapia that could withstand both high salinity levels and high temperature – a fish ideal for growing in desert ponds near the ocean. Israel comprises vast areas of land where the conditions are too arid for traditional crop growth and the available underground water is too salty for many animals and plants. Fishelson’s hybrid tilapia was therefore welcomed with open arms by Prof. Fishelson’s fellow countrymen.
When fish is farmed in countries where water is a scarcity, the water is usually meticulously managed. Instead of releasing the water at each harvest, a practise common among fish farmers living in more humid parts of the world and one which can easily lead to overt-fertilization of nearby water ways, the water is saved and used to grow algae. They algae will grow quickly by feeding off the organic waste products left by the fish and can soon be harvested as food for cattle and poultry or be sold for use in industrial products like dye and medicine. But this is not enough; once the algae are gone the water can be used to irrigate salt-tolerant crops like tomatoes to yield a third harvest.
In addition to being remarkably tolerant to salt and heat, Fishelson’s hybrid tilapia exhibits a strangely skewed sex-ratio. When certain species of tilapia are crossed, the resulting offspring will be virtually all male and Fishelson’s hybrid tilapia. Any females in the batch are normally the result of foreign genetic material in the parent fish, caused by earlier hybridization. Tilapia readily hybridizes with closely related species even in the wild.
In Fishelson’s hybrid tilapia, roughly 95% of the offspring is male which has made it an appreciated choice for fish farmers since fish that do not spend any energy on reproducing reaches a marketable size faster. Male tilapias are also known to grow faster and bigger than females.