Chapter 15: Tilapias
Tilapia are one of the most commonly cultured species in the tropics, adaptable to a variety of culture techniques. They are native to Africa and portions of the Middle East, but have been introduced into almost all remaining tropical countries as well as many temperate ones. They are true tropical species and will not survive at temperatures of 8 to 10°C and below. The name tilapia refers to over 100 species divided between the genera of Oreochromis, Sarotherodon, and Tilapia. Much of the earlier literature uses Tilapia as the genus name for the three groups now recognized as separate genera, but tilapia remains as the common name for all three.
Substrate spawners, such as Tilapia rendalli and T. zilli (Figure 15.1) have been cultured for aquatic weed control, or in production systems relying on the addition of macrophytes as a feed. Pond production of T. rendalli can be increased feeding a pelleted feed but yields are much lower that obtained with Oreochromis species. Few hatchery techniques have been developed specifically for T. rendalli or T. zilli. They are both prolific species capable of spawning numerous times a year in a static water pond, and if not harvested frequently will result in stunted populations. Stunted T. zilli females as small as 7 cm, weighing 12 g, have been found to be sexually mature, similarly males as small as 5 cm weighing <8 g were mature.
Pitted saucer-shaped nests are made by T. rendalli while T. zilli makes a cluster of 5 to 10 small holes in the pond levee or bottom that can damage the levee (Figure 15.2). Both parents will build the nest and guard the eggs. A female may spawn as frequently as every 26 days releasing on average over 3000 eggs/spawn. The eggs hatch in about 5 days. The male will aggressively defend the nest sites and the fry for several weeks. Most-appropriate hatchery techniques for producing T. rendalli or T. zilli are not well established. A spawning-rearing technique may be acceptable for the hatchery production of this group, but care must be given to not allow the pond to become overcrowded.
Among the mouth brooding tilapias Oreochromis aureus, O. mossambicus, and O. niloticus are the most commonly cultured tilapias, with O. niloticus the predominate species cultured. They spawn naturally in ponds with no manipulation of the environment needed to induce spawning when the temperature is 23°C and above. The males sweep out bowl-shaped nests in the shallow areas of a pond (Figure 15.3). A male and a female spawn in the nest over a period of up to two hours. A batch of eggs is deposited in the nest by the female, fertilized by the male, and then the eggs are picked up by the female and held in her mouth. This is repeated several times until spawning is complete. The female will then incubate the eggs in her mouth (Figure 15.4) until hatching and may shelter the fry in the mouth until through the swim-up stage. The reproductive cycle for a female is about one month, but can be shortened by collecting eggs or fry from the female’s mouth.