The tilapia They include a group of fish from Africa that are used by man mainly due to their high productivity and rapid development characteristics. The genera to which these fish belong are typically Oreochromys, Tilapia and Sarotherodon.
Of these genres the most important is Oreochromis, which includes 32 species of fish, most of which are severely affected by human activities and are included in worrying global threat categories. Hybridization with species of the same genus introduced in the distribution areas of the others, represents one of the strongest threats.
Tilapias generally have a diurnal activity. During the day, they feed and reproduce and during the nights they usually move into deep waters..
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These fish have typical characteristics of cichlids (Cichlidae family). They are laterally flattened fish with an incomplete lateral line that is typically interrupted at the level of the dorsal fin and they have deep bodies. The body is lined by relatively large and fairly resistant cycloid scales.
The dorsal and anal fins have strong spines and soft rays; the pelvic and pectoral fins are larger and anterior, which allows them better performance in swimming and maneuverability. The number of scales, the number of vertebrae and the number of gill spines is variable and characteristic of each species..
Males have well-developed, swollen mouths. Adults have a tricuspid dentition, associated with herbivorous habits, although they consume a wide variety of resources during their development..
Tilapia bodies typically have lightly colored vertical bars that contrast little with the striking coloration. This gives these fish the ability to change color in response to changes in environmental conditions by controlling chromatophores..
The eyes are well developed which gives them good visibility, they also have large nostrils and an obvious lateral line.
The taxonomy and classification of tilapia is quite confusing and is subject to continuous change due to the morphological similarity of many of the related species and genera..
Currently the genre Oreochromis it has 32 recognized species. Other genera of tilapias such as Sarotherodon Y Tilapia they have 13 and 7 species respectively.
These fish reach sexual development very quickly, so the species can constitute an ecological risk when it is introduced in areas where it is not native. Tilapia species reach maturity very quickly. This occurs, since they reach a weight between 30 and 50 grams and can breed in fresh and brackish water.
Females can lay several clutches a year. In very favorable temperature conditions they can carry out 4 to 5 layings in a year. The number of eggs per clutch varies according to the development of the females. Despite this, the total number of eggs ranges between 200 and 2000 in the best-studied species..
When the female is ready to mate, it generally descends in the water column and goes to the bottom where the males have prepared a kind of enclosure or nest for the eggs, which can reach two meters in diameter and 60 cm deep..
After a brief courtship presented by the male, the female begins to lay the eggs, which are fertilized when the females oviposit..
Once fertilized, the eggs are protected by the female in her oral cavity where they are protected until they hatch. After a short incubation period that ranges from three days to three weeks, depending on the temperature and the species, the eggs hatch..
The fry can remain in the mouth for a period of two weeks. Upon release, they remain close to the mother for a few days and, when threatened, quickly retreat to their mother's mouth. The fry then settle in areas with shallow water.
The period of parental care of the fry can be extended for a period of two to three weeks. On some occasions the males can protect the eggs in their mouth, however, they are frequently consumed by this.
The female resumes her feeding activities after abandoning the young and recovers the condition of her ovaries quickly, around four weeks, to prepare for a new oviposition..
In nature these fish feed on a wide variety of items. In their early growth stages, fingerlings feed on phytoplankton and zooplankton. Debris is also an important resource in the diet.
After the first stages, the juveniles assume a more complex and varied diet that includes a large number of aquatic crustaceans such as copepods and cladocerans..
In addition to these, they consume other assorted bottom-dwelling invertebrates, from which they can extract pieces. They can consume various aquatic insects and their larvae, as well as worms and shrimp. Due to the broad spectrum of the diet of growing individuals they are considered omnivores / carnivores.
The adults of most species have tendencies to be herbivorous, being able to consume from algae to aquatic plants and riparian vegetation.
It has also been reported that in certain situations, when food availability is low, individuals of larger sizes can take advantage of smaller fish of other species and even eat members of the same species..
In those habitats where they have been introduced into natural environments, they have managed to displace and eliminate native species as they also feed on their eggs..
There are three most important species found under the name of Tilapia, Oreochromis aureus, Oreochromis niloticus Y Oreochromis mossambicus.
This species is recognized by the presence of between 14-17 rays in the dorsal fin, between 11-15 anal spinal rays, 8-11 soft anal rays and between 28-31 vertebrae. Adults have narrow preorbital bone. The lower pharyngeal jaw has a short blade, the lower jaw does not exceed 36% of the length of the head.
The caudal fin does not have dark vertical stripes but the distal margin is pink or bright red. In breeding females it is usually orange in color. Breeding males have an intense and bright bluish color on the head and a more intense pink on the tail fin..
This species reaches maturity in an optimal range between 13 and 20 cm. They can reach lengths of up to 46 cm with a maximum weight of 2 kg. It is a cold tolerant species, occurring at temperatures that vary between 8-30 ° C.
In addition, it tolerates fairly brackish conditions. It is usually territorial in confined spaces, inhabiting ponds, warm reservoirs, lakes and streams both in open waters and spaces reduced by rocks and vegetation..
Black tilapia can occupy varied fresh and brackish water habitats, generally at a depth of up to 12 meters in the body of water and with temperatures between 17 and 35 ° C. The reproductive maturity range is between 6 and 28 cm reaching an average total length of 35 cm.
It has 15-18 dorsal spines, 10-14 soft rays on the dorsal fin, 3 anal spines, 7-12 soft anal rays and 28-31 vertebrae. The muzzle is long, the forehead has relatively large scales. They have two scales between the eyes followed by a continuous row of nine scales up to the dorsal fin.
Males have a sharp snout relative to females and have enlarged jaws. Non-breeding males and females are brightly colored with 2 to 5 lateral spots. Breeding males are characteristically black with white underparts.
It is a euryhaline species, which indicates that it supports a high salinity range. It prefers estuarine habitats or lake bodies close to the sea without occupying permanently open estuaries and the open sea. In addition, it can tolerate environments with low oxygen availability..
Red tilapia is characterized by the presence of 15-18 dorsal spines, 11-13 dorsal soft rays, 3 anal spines, 9-11 soft anal rays, and 30-32 vertebrae. Reproductive maturity is reached in a range between 6 and 28 cm. Reaches lengths of up to 60 cm and weighs 4.3 kilograms.
It is one of the tilapias with the highest body mass, the head is relatively small compared to other species. In sexually mature males, the jaws are not very enlarged and occupy about 30% of the length of the head. The genital papilla of the male does not have tassels.
The most striking feature of this species is the presence of regular vertical stripes throughout the depth of the tail fin. Adult males are usually bluish-pink in color, with dark throat, belly, anal and pelvic fins. Females have a silvery-brown coloration and are clear ventrally..
The species is not very tolerant of low temperatures or brackish conditions, however, it can survive in a small salinity gradient. Its activity is mainly daytime. It is the most important tilapia species worldwide in fish farming and consumer production activities..
Many of the countries in which tilapia species have been introduced into natural ecosystems, intentionally or by accident, have reported some degree of ecological impact. The aggressive and voracious characteristics of many of the species make them highly competitive with respect to native species.
The high reproductive rate and rapid development has allowed this species to easily outcompete and displace other species. The latter has caused in many localities where they have been introduced, a critical decrease in local species and even their extinction..
On the other hand, the introduction of the Nile tilapia, very adaptable to a wide range of temperatures and other environmental conditions, has caused hybridization with other species of Oreochromis, which irreversibly affects the genetic integrity of these populations and they are currently very close to disappearing.
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