Yellow-belly bream

Dorsal spines (total): 15-16; Dorsal soft rays (total): 13-16; Anal spines: 3; Anal soft rays: 10-11. Diagnosis: The presence of four or five scale rows between the posterior margin of the orbit and the ascending arm of the preoperculum, the presence of widely set unicuspid teeth on the jaws, widely separated gill rakers, and anal fins with egg ocelli places this species in Serranochromis (Ref. 128638). Breeding males of S. robustus possess ocelli that are restricted to the posterior 4-5 membranes of the anal fin, which delimits them from all other Serranochromis species, which have ocelli throughout the anal fin in breeding males, with the exception of S. jallae (Ref. 128638). Serranochromis robustus generally has a longer lower jaw than S. jallae, 50.7-59.6% of head length vs. 49.2-52.7%; it is not as deep-bodied as S. jallae as evidenced by the distance between the posterior insertion of the dorsal fin and the posterior insertion of the anal fin, 13.4-15.1% of standard length in S. robustus vs. 14.9-18.4% in S. jallae; additionally, S. robustus has a narrower least caudal peduncle depth than S. jallae, 10.9-12.8% of standard length vs. 11.3-14.2%, the least caudal peduncle depth of all S. robustus was less than 12.8% of standard length while for S. jallae, except for the smallest specimen, the least caudal peduncle depth was greater than 13.2%; Serranochromis robustus has a smaller horizontal eye diameter than S. jallae, 17.7-27.4% of head length vs. 18.6-25.5%; in general, S. robustus has more teeth in the outer row of the left lower jaw than S. jallae, 14-23 vs. 13-14 (Ref. 128638). Adults in breeding colour of Serranochromis robustus are blue/green laterally with a narrow yellow marginal band on the dorsal fin and usually a small yellowish tip to the upper caudal-fin lobe; adults in breeding colour of S. jallae are yellow/green laterally with a bright orange marginal band on the dorsal and caudal fins in fish from the Okavango River system, but creamy yellow bands in fish from the upper Zambezi River system; the throat and belly of S. jallae becomes more intensely yellow-orange in breeding dress hence the local name 'yellow-belly'; rarely, specimens from the Okavango River in Namibia also have yellow rather than orange marginal bands (Ref. 128638).