The Blue Tilapia (Oreochromis Aureus)
Blue tilapia (Oreochromis aureus) is also known as Israeli tilapia. It is an appreciate food fish and a common species in aquacultures worldwide. Blue tilapia is also sold as bait and aquarists keep it as a pet.
Habitat and geographical range
Oreochromis aureus is native to Cameroon, Chad, Egypt, Israel, Jordan, Mali, Niger, Nigeria, Saudi Arabia, and Senegal in tropical and subtropical African and the Middle East. It can for instance be encountered in the Jordan Valley, the Lower Nile, the Chad Basin, the Benue River, the middle and upper Niger, and the Senegal River.
Since Oreochromis aureus is such a popular food fish, it has been introduced by man to many other parts of the word through aquaponics, such as South East Asia and the Americas.
Oreochromis aureus lives in both freshwater and brackish environments, but it is most common in freshwater. In a few locations, it actually occurs in marine waters. Even though it hails from the tropics and subtropics it occurs at temperatures ranging from 8 to 30 degrees C (47 to 86 degrees F). It can tolerate a water temperature up to 41 degrees C (106 degrees F). A minimum temperature of 20-22 degrees C (68-72 degrees F) appears to be necessary for reproduction to occur.
Oreochromis aureus can adapt to many different types of habitats and occurs in open water as well as in densely grown environments. It lives in lakes, streams, ponds and impoundments.
Blue Tilapia Appearance
The largest scientifically measured Blue tilapia was 45.7 cm in length. The maximal published weight is 2,010 grams. The caudal fin of the Blue tilapia has broad bright red or pink distal margin. During the breeding period, the head of the male fish will change into a bright metallic blue shade and he will also display a vermilion coloration on the edge of his dorsal fin and an intense pink coloration on the margin of his caudal fin. A breeding female fish will develop a pale orange color on the edges of her dorsal and caudal fins.
Blue Tilapia Behavior
Blue tilapias form schools. They can sometimes be territorial.
Blue Tilapia Feeding
Young Blue tilapias eat a varied diet while adult fish tend to be fairly strict herbivores. Young Blue tilapias are known to include plenty of copepods and cladocerans in their diet and they will also eat small invertebrates if they get a chance. Adult fish feed chiefly on phytoplankton and epiphytic algae, combined with zooplankton once in a while. Blue tilapia can occasionally eat small fish. Blue tilapia seems to adapt their diet to the surrounding environment, because research carried out in different bodies of water has yielded different results.
Blue Tilapia Reproduction
Just like many other African cichlids, the Blue tilapia is a maternal mouth brooder. The male will build a nest and defend the territory. If his displays are not enough to fend of intruders, he can engage in mouth fighting. During spawning, the female fish will release her eggs in the nest and the male will fertilize them there. After fertilization, the female fish will pick up the eggs and head for deeper waters. She will keep eggs, larvae and fry in her mouth until the fry are large enough to be released.
Female Blue tilapias will usually reach sexual maturity when they are around 10 cm long (almost 4 inches), but reports of smaller females with ripe ovaries do exist.
As mentioned above, Blue tilapia seems to require a minimum temperature of 20-22 degrees C (68-72 degrees F) to breed. The species can reproduce both in fresh and brackish waters.
Conservation status for Oreochromis aureus
Oreochromis aureus has not been evaluated for the IUCN Red List of Threatened Species.
Oreochromis aureus as an invasive species
Blue tilapia that is introduced to non-native waters can be become a problematic invasive species. Compared to many other tropical fish species, it is fairly cold resistant and can therefore survive even in warm temperate environments. Studies indicate that the fish is more cold tolerant in waters with low salinity (5 ppt) than in freshwater. It should however be noted that Blue tilapia seems to require a minimum temperature of 20-22 degrees C (68-72 degrees F) to breed.