Oreochromis mossambicus

Geographical range and conservational status
Despite its name, the Mozambique Tilapia (Oreochromis mossambicus) is not only native to Mozambique; it can also be found in Malawi, Swaziland, Zambia, Zimbabwe and South Africa. You can for instance encounter it the lower Orange River, in the rivers of Namibia, in Bushmans River, in the Lower Zambezi and Lower Shire, and in Transvaal in the Limpopo system. In its native range, Oreochromis mossambicus is listed as Near Threatened (NT) on the IUCN Red List of Threatened Species. The main threat against the survival of the species is its willingness to hybridize with other tilapia species.

Due to its popularity as a food fish, the Mozambique Tilapia has been introduced by man to many other parts of the world, including some subtropical and even warm temperate parts of the globe. In some places, Oreochromis mossambicus have become a problematic invasive species. You can find more info about this further down in this article.

Mozambique tilapia habitat
The adaptable Mozambique tilapia lives in many different habitats but is not found in fast-flowing rivers and streams. It is primarily a freshwater species but there are thriving populations to be found in estuaries as well as in salty coastal lakes, especially in the southern part of its geographical range.

This fish can tolerate temperatures from 40 degrees F (4.4 degrees C) to 104 degrees F (40 degrees C) and it is also very resilient to organic waste, low oxygen levels, and many types of pollution.

The Mozambique tilapia is a laterally compressed fish with a deep body. The body is predominantly yellow, but the exact colouration and pattern varies within the species. Mozambique tilapias have a long dorsal fin with protective spines.

Oreochromis mossambicus is an opportunistic omnivore that feeds on a long row of items, such as insects, fry, aquatic invertebrates, higher plants, diatoms, macroalge, and detritus (decomposing organic matter). It is however chiefly a filter feeder; it filters plankton out of the water and secrets a special mucous that traps them.

To extract sufficient amounts of nutrients from plankton, the Mozambique tilapia grinds them between its two pharyngeal plates and this fish also has a highly acidic stomach where the pH-value stays around 2. When the grinded planktons come in contact with the acid, their cells burst.

Oreochromis mossambicus is a flexible species so its exact diet will vary depending on available food sources. Tilapias living in one location may therefore stick to a very different diet than members of the same species living somewhere else.

Mozambique tilapia in aquacultures
Due to its sturdiness and adaptability, the Mozambique tilapia is a fairly common sight in fish farms around the world but it is not one of the most favoured species. It is a much appreciated food fish with white and mild flesh, but despite this Oreochromis mossambicus make up no more than approximately 4 percent of the total global tilapia aquaculture production. The species is however used extensively by the industry to create new hybrids and strains, since it has a lot of desirable traits.    

Keeping Mozambique tilapia in aquariums
Since this species can exceed a length of 40 cm (16 inches) it is only kept by aquarists with large and roomy aquariums. It is usually offered as a small, juvenile specimen but it grows really fast so don’t get it unless you know where they house it when it reaches its adult size. It is quite a messy eater to be prepared to carry out frequent water changes. Young specimens are quite docile but older ones tend to become aggressive and hostile towards other fish.
Mozambique tilapia is an omnivore and very easy to feed in captivity, but you can’t house it with any animal small enough to be considered prey and it might damage live plants. Keep it on a varied diet, e.g. by feeding it a base of prepared foods like green flakes, pellets and algae wafers combined with fresh vegetables and occasional servings of meaty live or frozen foods, e.g. shrimps and mosquito larva.

Oreochromis mossambicus breeding
Oreochromis mossambicus readily breeds in ponds and is not very tricky to breed in aquaria either. Sexing is tricky since both sexes look very similar, so most breeders keep a group of at least 5-6 juvenile specimens together and let them form their own pairs as they mature. This tilapia usually attains sexual maturity at an age of 8-9 months.

Once a pair has been formed, the male will dig out a saucer-shaped nest in the bottom substrate, so make sure you use sand in the aquarium. Coarse gravel can injure the fish. The female will then place her eggs in the nest and the male will fertilize them.

Like many other African cichlids, Oreochromis mossambicus is a maternal mouthbrooder, i.e. the female fish protects the offspring inside her mouth. In many African cichlid species the female will pick up the eggs before they are fertilized and let the male fertilize them inside her mouth, but Oreochromis mossambicus females do not pick up the eggs until they’re already fertilized. The eggs will hatch inside her mouth (typically within 3-5 days) and the fry will stay inside until she deems them large enough to be released. Don’t expect to see any fry in the water until at least 10-14 days after the eggs hatched.

As soon as the fry is released you can start feeding them powdered flakes and newly hatched brine shrimp. In the wild, newly released Oreochromis mossambicus fry seek out shallow waters where they form a small school and they will try to carry out this behaviour in the aquarium as well.

Once the couple has spawned for the first time you can expect them to get a new batch of fry every 3-4 weeks throughout the breeding season.

Conservation status for Oreochromis mossambicus
As mentioned above, Oreochromis mossambicus is listed as Near Threatened (NT) on the IUCN Red List of Threatened Species, with the main threat against it being hybridization with other tilapia species. With the help of anglers and fish farmers, the O. niloticus (Nile tilapia) has entered into the geographical range of O. mossambicus in the Zambezi and Limpopo systems. The IUCN fears that O. mossambicus will soon be extinct in those systems.

Oreochromis mossambicus as an invasive species
Oreochromis mossambicus has been nominated to the group “100 of the World’s Worst Invasive Alien Species” by the IUCN Invasive Species Specialist Group (ISSG).

When introduced to regions outside its range, Oreochromis mossambicus can easily become a problematic invasive species that disrupts the local ecosystem. The Mozambique tilapia is for instance responsible for a sharp decline in the number of Striped mullets (Mugil cephalus) in Hawaii, and it has also been fingered as the culprit behind the dwindling populations of Desert pupfish (Cyprinodon macularius) in California’s Salton Sea.