![]() ![]() This requires hatcheries to be set up in such a way that brooding females can be easily captured and their eggs/fry “robbed” on a regular basis. To be able to consistently produce high proportions of males (over 99%), hatchery managers need to begin the sex-reversal treatments on young fry, at first feeding. The difficulties described in trying to generate all-male fry through the use of hybridization means that most hatchery managers have turned to methods of direct sex-reversal of fry, using 17α-methyltestosterone in the feed. Single sex populations also reduce size differences in harvested fish related to the sexual dimorphism in growth performance between male and female fish. Most largescale production systems try to produce single sex male fry to minimize problems associated with breeding and fry production during grow out, particularly in pond-based systems. The breeding behavior of tilapia has a major impact on the hatchery techniques used to produce the large numbers of fry needed by ongrowers. This behaviour can last for several weeks in the wild ( Turner and Robinson, 2000). However, if the fry are threatened they will return to the female’s mouth. The female will then move into shallow water to release the fry to minimize predation. In Oreochromis, which are maternal mouthbrooders, it is the female alone that picks up the eggs and incubates them in her mouth, moving to more protected areas away from the lake until the fry are ready to feed, roughly 10–12 days postfertilization. In the case of Sarotherodon, which are paternal or biparental mouthbrooders, either the male or both the male and female will pick up and incubate the eggs in their mouths. In the mouthbrooding Sarotherodon and Oreochromis species, small batches of eggs are laid by the female and fertilized by the male. Both parents will then guard the eggs and young. the female lays eggs that stick directly to the bottom of the nest and the male fertilizes the eggs in situ. However, most have a flexible and opportunistic feeding behaviour, which has made them ideal species for aquaculture.Īll tilapias are lek-spawners, in that the males dig circular nests in areas with a suitable substrate and females are attracted into the area and will enter and mate with the male. have coarse pharyngeal teeth and few gill rakers and tend to eat higher plants whereas the Sarotherodon and Oreochromis have finer teeth and gill rakers and are predominantly microphagous, grazing on epiphythic and benthic algae, detritus and filter feeding on plankton in more open environments ( Trewavas, 1983). ![]() Tilapia are primarily herbivorous and detritivorous feeders: Tilapia spp. Tilapias are naturally found in a wide range of tropical and subtropical African riverine and lacustrine ecosystems with some of the species also entering brackish water estuaries and lagoons. ![]() Stefanie Wehner, in Genomics in Aquaculture, 2016 Life history ![]()
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