Tilapia is the third most-produced fish in the world due to its multiple productive and reproductive advantages.

Tilapia production in the world

Tilapia is the third most-produced fish species in aquaculture worldwide. Currently, the main producer of tilapia in the world is China with 1.7 million metric tons (MT). This species originated on the African continent and was introduced to China in the late 1970s. The other major producers of tilapia in the world are Indonesia and Egypt. Indonesia produces 1.1 million MT while Egypt produces 900,000 MT each year. For the last one, production is expected to increase by 10% this year.

On the other hand, the largest importer of tilapia is the United States. During the second half of the 20th century, tilapia spread to all continents for production.

Tilapia production has been increasing every year. In 2010 there was a production of 2,657.7 million tons, while in 2018 it reached 4,525.4 million tons. Tilapia in 2018 represented 8.3% of the entire world’s production of aquaculture species, ranking it as the third-largest producer.

Tilapia generalities

Tilapia of the species Oreochromis niloticus (Linnaeus, 1758) is the most widely used in aquaculture production. It is also called Nile tilapia due to its geographical and historical origin. It has an average life of 10 years and can weigh up to 5 kg.

It is considered a tropical species, which makes it a species with a great capacity to adapt to all producing countries. In addition to this, it is a very prolific and resistant species. They are colloquially called “the chickens of the water” due to their efficient production capacity. The reproductive cycle of tilapia explains this high capacity.

1. Rapid growth: Tilapia can reach 1 pound in 6 months.
2. Known reproduction: the reproductive cycle of tilapia is widely known.
3. Good reproduction: it has a high spawning rate, high fertilization rate, and high viability of larvae.
4. Easy handling: resistant to handling, diseases, and environmental changes.
5. Tolerates high densities: tilapia outperforms intensive or super-intensive farming, which lowers production costs.

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Reproductive aspects of tilapia

Sexual differentiation (sexing) in tilapia

An important part of the tilapia reproductive cycle is sexing. For this, some characteristics of each sex are considered. In the male, the tilapia has two orifices under the belly, corresponding to the anus and the urogenital orifice. Meanwhile, in the female, three orifices are observed: the anus, the genital pore, and the urinary orifice. Of these, the anus is always visible, being a round hole. The urogenital orifice of a very small point. Finally, the urinary orifice of the female is in the slit perpendicular to the body.

Nile tilapias reach sexual maturity at 3 to 4 months of age. At this point, its weight will be between 50 and 100g and its length will be between 10 and 12 cm. These are the optimal parameters for a successful tilapia reproductive cycle. Regarding temperature, the ideal temperature for spawning is between 25-30°C (77-86°F). This will allow a quantity of eggs between 100 to 2000 per female.

Tilapia reproduction process

The reproductive cycle of the tilapia begins with the male tilapia searching for a territory where he begins to dig until he forms a hole that will become the nest. From there, the male tilapia cares for and guards this nest. The female tilapia, when mature, spawns in this nest. Once the male has fertilized them, the female collects the eggs again by holding them in her mouth and leaves. In the mouth, the Tilapia eggs carry out their incubation process until the yolk sac is absorbed.

Due to this oral incubation process, the number of eggs per oviposition is lower compared to other fish species. On the other hand, this number of eggs also depends on the weight of the female. For example, a 100g female will lay approximately 100 eggs. On the other hand, the male can fertilize the eggs of different females, which is an important feature of the tilapia reproductive cycle.

Tilapia reproductive cycle management

The tilapia reproductive cycle and its other production stages can be done with several farming systems.

1. Extensive culture: it has a density of 1-2 fish/m3.
2. Semi-intensive culture has a density of 3-8 fish/m3 and requires a 50% water change every week and filtration systems.
3. Intensive culture: has a density of 10-15 fish/m3 and uses high-capacity concrete piles, plus an aeration system.
4. Super intensive culture has a density of 30-100 fish/m3 and uses concrete piles or high-capacity floating cages. It requires a 100% water change.

Sexual reversion

In commercial tilapia farming, only male (monosex) populations are managed since body growth is favored. To achieve this, some techniques have been implemented

1. Manual sexing: 85% accuracy, it is avoided because it can fail.
2. High-density culture
3. Crossbreeding with other tilapia species.
4. Experimental: to obtain sterile triploids; or super males with YY chromosomes.
5. Sexual reversion with hormones: this is the most used method.

Sexual reversion with hormones is the most used method within the tilapia reproduction cycle. This sexual reversion is part of the tilapia reproductive cycle to avoid growth disparity in mixed populations (females and males), dwarfism, or competition. In addition, monosex populations of males are obtained, which grow twice as fast as females, have better fat deposits, and avoid overpopulation.

For sexual reversion in tilapia, androgenic hormone 17-alpha-methyl-testosterone is first applied to the larval diet before yolk sac absorption (3 days after hatching). At this point, the gonads will not yet have developed in the larvae and the females will become phenotypically male. They are then fed with this mixture for 30 days or until the fry are less than 18 mm long.

It is mentioned that the efficacy of sexual reversion varies from 95 to 100%. However, if the success of sexual reversion of tilapia is to be tested, a significant percentage of the population (10%) is taken. These animals should weigh more than 50 grams and are sacrificed for abdominal dissection. Then, the development of testes or ovaries and the relationship of these individuals with the population are checked.

Obtaining fry

After the eggs are fertilized, the female incubates them and carries them in her mouth to protect them. When the fry hatch, they should be planted in ponds at a density of 20-25 fry/m3 for 2 to 3 months, until they reach 30-40g in weight.

After the reproductive cycle of the tilapia and the production of fry, they must pass to the fattening stage. Four main techniques have been used for this stage: ponds, floating cages, fast flow channels, and recirculation systems.

CONCLUSIONS

Tilapia is one of the most productive aquatic animals in the world. To achieve good production rates, it is important to know the reproductive cycle of tilapia. This stage of production is critical to the success of tilapia aquaculture. Parts of the tilapia reproductive cycle include sexual behavior, fertilization conditions, sex reversal, feeding, and fry production.