Mozambique Tilapia, Oreochromis mossambicus
The Mozambique Tilapia, Oreochromis mossambicus, whose Spanish common name is tilapia del Mozambique, is a species in the family Cichlidae, the Cichlids and Talapias, are known as tilapias and mojarras de agua dulce in Mexico. They are native to Southern Africa and via human introductions they are now found throughout the global tropical and subtropical locations. Globally, there are thirty two species in the genus Oreochromis, four of which are found in the majority of freshwater systems within Mexico. They were introduced and cultivated in Mexico in the 1950s with fish being imported from Africa.
The Mozambique Tilapia has an overall “bluegill profile” with a deep compressed body. Coloration can vary significantly and they can be blue, black, dull greenish or yellowish with the lower portion of the head being white. The margins on the caudal and dorsal fins are red with weak banding. When spawning the caudal and pectoral fins becoming reddish with the males’ tail being a brighter orange than those of the females. Females and non-breeding males are silvery with two to five mid-lateral blotches and three or four dorsal blotches. The head shows sexual dimorphism with males having an upper jaw length and the mouth that is larger than those of the females and also a blue upper lip. The head is mid-sized with modest sized eyes and they have a knob like protuberance behind the upper jaw. The anal fin has three spines and nine or ten rays; the caudal fin is rounded; and, the dorsal fin has fifteen to eighteen spines and ten to thirteen soft rays and is continuous with a long base. They have sixteen to twenty two gill rakers on the first arch and the lateral line is interrupted. The body is covered with cycloid scaled.
The Mozambique Talapia are found in rivers and lagoons predominantly in fresh water but they can also tolerate fairly high levels of salt and are also found in brackish waters normally with dense aquatic vegetation. They are residents of all Mexican fresh water environments that do not drop below 11oC. They weight up to 1.1 kg (2.5 pounds) and the maximum recorded length is 40 cm (16 inches) with males being larger than females. They are opportunistic omnivores consuming diatoms, invertebrates, small fry and vegetation ranging from macroalgae to rooted plants to decaying plant material. They are active diurnally. Reproduction occurs year round when water temperatures are in excess of 20oC with each female raising new broods every three or four weeks. There is intense competition amongst males for nesting sites. Once selected the males excavate a three-foot diameter saucer shaped nest in sand or small gravel in which the females lays her eggs. After fertilization by the male the female collects the eggs and stores them in her mouth until the fry hatch (mouthbrooding) in one to three weeks and the fry remain for another two weeks. They exhibit a high level of parental care with the females caring for the young and the males providing protection. These families are thus highly mobile. These proficient reproductive strategies are supportive of their invasive tendencies. They have lifespans of up to 11 years.
Mozambique Tilapia are similar to, and can be mistaken for the Blue Tilapia, Oreochromis aureus (18 – 26 gill rakers on first arch) and the Nile Tilapia, Oreochromis niloticus (27 – 33 gill rakers on first arch).
Mozambique Tilapia are a prime farmed fish because they are hardy individuals that are highly adaptable to new environments, differing water conditions, changes in food supplies, and have a high tolerance for high levels of ammonia, low levels of oxygen, general pollution and have an ability to survive drought by burying in moist sand. They can grow and reproduce in waters with a relative high salt content. It is a popular food fish with white, mild flesh and they are marketed live, fresh and frozen. The Mozambique Tilapia, is more commonly used for hybridization with other tilapia species. The hybrids grow faster, have a better body shape, and in some species the populations will be predominantly male (which will grow faster to a uniform size). Under crowded condition cannibalization will occur and also the fish will become stunted. This species is produced at a level of 40,000 tons per year and constitutes about 4% of the total global tilapia aquaculture production. Mexico is currently only being a small player in this global market.
Surprisingly the Mozambique Tilapia is currently listed as Near Threatened. They have been introduced into water systems by anglers, fish farmers and government agencies, for aquatic plant control, insect control, sport fishing, bait fish, and as a food fish and through aquarium releases, escapes from fish farms, hatcheries, and zoos. When introduced to bodies of water that contain the Nile Tilapia, Oreochromis niloticus, the two readily mate which leads to hybridization and to the long term extinction of the Mozambique Tilapia in those systems is assured. As approximately 50% of the current native locations for the Mozambique Tilapia have not yet invaded by Nile Tilapia significant efforts are on-going to protect these systems from deliberate and accidental introductions of Nile Tilapa. They provide strong competition with native fishes for nesting places and food including the direct consumption of small fishes. As such the Mozambique Tilapia has the dubious distinction of being considered to be one of the 100 worst invasive species in the world. Mozambique Tilapia can be used as aquarium fish, however they become excessively large very quickly. They are also a dirty fish that requires frequent water changes and old species become increasingly aggressive. They are also used to bioassay organisms to generate metal toxicity data for risk assessments of water bodies containing local freshwater species.