Photo credit: Michael Hayes, https://flic.kr/p/4GQSS3
Photo credit: Cody Hough, https://flic.kr/p/L3jqNN
Blue Tilapia and Redbelly Tilapia
(Oreochromis aureus and Tilapia zillii)
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Species at a Glance
Tilapias are resilient, prolific, easy to grow, and appeal to many consumers with their mild flavor and white flesh. Therefore, species like the blue and redbelly tilapia have become economically important food fish throughout the world. Unfortunately, escape into the natural environment has given them the potential to outcompete native species and negatively impact aquatic communities.
The body of the blue tilapia is blue and silver with dark vertical bars that may not always be apparent. Dark and light spots alternate on the posterior half of the dorsal fin and the upper margin is red or orange in color. The caudal fin also has a broad pink to red margin. The eye has a red iris that is crossed by a black bar. Males are significantly larger than females, reaching a maximum length of 50 cm (20 in). Breeding males exhibit a bright metallic blue on the head and a more intense pink on the fins, as well as a blue-black chin and chest.
The redbelly tilapia is olive-colored on top and light olive to yellow-brown on the sides, often with an iridescent blue sheen. Lips are bright green and the chest is pinkish. Six to seven dark vertical bars cross two horizontal stripes on the body and caudal peduncle. Fins are covered in yellow spots, with the dorsal and anal fins displaying the outline of a thin orange band. Spawning coloration is a shiny dark green on the top and sides, red and black on the throat and belly, and obvious vertical bars on the sides. The heads turn dark blue to black with blue-green spots. It reaches a maximum length of 40 cm (15.7 in).
The blue tilapia has little or no breeding coloration in males in contrast with the redbelly tilapia. The redbelly tilapia is also similar to the spotted tilapia (Tilapia mariae), but differs in that the spotted tilapia lacks the blood red coloration, it has 5-6 black square blotches on its side, and the stripes on its side extend onto the dorsal fin.
Both tilapia species can be found in lakes, wetlands, marine habitats, watercourses, and estuaries. They prefer tropical habitats, but the blue tilapia can tolerate cold temperatures as low as 8°C (46°F). The redbelly tilapia has the ability to establish in highly salinated waters. Both species are considered hardy and tolerant of a wide range of water quality and habitat conditions.
Tilapia introductions have occurred through many vectors, including intentional stocking for experimental work by states and private companies, as forage for warm water predatory fish, as a food source, as a control for aquatic plants, and through unintentional escapes.
Native to parts of Africa and the Middle East, blue and redbelly tilapia were annually stocked in states like Alabama and Arizona from the late 1950s to the 1970s. They can now be found established in several states throughout the U.S. and in the Mid-Atlantic region in North Carolina and South Carolina.
Note: Distribution data for this species may have changed since the publication of the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016), the source of information for this description.
These tilapias have the ability to spread rapidly and in large numbers, allowing them to effectively compete with native species for food and nesting space. The redbelly tilapia can also alter native benthic communities through the elimination of plants, and will often exhibit aggressive behavior towards other fish.
Information for this species profile comes from the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016).