Oreochromis leucostictus

Oreochromis leucostictus (the blue-spotted tilapia) is a species of cichlid native to Albertine Rift Valley lakes and associated rivers in DR Congo and Uganda. It has now been introduced widely elsewhere East Africa, and is believed to have negative ecological impact, particularly on native tilapias. This species is reported to reach a standard length of up to , but is usually much smaller. It is exploited by small-scale fishery and aquaculture operations. Oreochromis leucostictus is a relatively deep-bodied tilapia with a fairly small mouth, narrow, rounded head and high back. Juvenile are pale, countershaded and have around 8 thin faint dark bars on the flank beneath the dorsal fin, with other bars on the head and tail. The fins are faintly spotted and there is a rather vague dark 'tilapia mark' at the based on the soft dorsal fin. Adults of both sexes are characterised by white spotting on the flanks and fins. Mature males are very dark, almost black, sometimes with a blue-green iridescence, and the white spots are very conspicuous. The eye is bright yellow and crossed by an oblique bar. Mature males have elongated filamentous tips to the dorsal and anal fins, but do not have enlarged jaws (in contrast to species like Oreochromis mossambicus). Young fishes have numerous small slender tricuspid teeth, but they become stouter in larger fish, and sometimes bicuspid. Overall, there are usually 4–6 rows of teeth, occasionally up to 8 in larger fish. The lower pharyngeal bone is slender, with numerous crowded teeth. There are 3–5 upper gill rakers, 1 on the angle and 19–23 lower rakers. The dorsal fin has 15–18 spines and 11–13 rays. The anal fin generally has 3-spines, although a single 4-spined individual has been reported, and 9–11 rays. There are 28–31 scales in the lateral line series. Adults are reported to grow to a total length of 28–30 cm in Lake Victoria, but they mature at much smaller sizes in smaller water bodies, with ripening females reportedly as small as 8 cm.