Labeotropheus trewavasae pair in Berlin Aquarium, photo copyright © by M.K. Oliver
Above, lower fish: L. trewavasae male of the normal BB or black-barred blue morph. Its orange- red dorsal fin is characteristic of males from Thumbi Island West and a few other southern populations. An OB (orange-blotch) female can be seen in back, incubating eggs in her mouth. Photo © by M.K. Oliver, taken at the old Berlin Aquarium, 1968.exporters in Malawi in the late 1960s and early '70s. Davies told me that he and his crew found only about one L. trewavasae "marmalade cat" per year, and asserted that they occurred only at the southern tip of Thumbi Island West (pers. comm. 4 July 1971). Individuals have since been found at a few additional, widely scattered localities, including Nkhata Bay (and transplanted from there to Likoma Island) and Pombo Rocks, Tanzania (Konings, 1995c: 130).
Only males occur in this blue-blotched "marmalade cat" form, which seems to be a male equivalent of the far more common OB (orange blotch) morph seen in females. The frequency of OB female L. trewavasae varies from locality to locality, approaching 95% at some spots (Konings, 1995c). Rare orange (O morph) females also occur, but the most frequent morph of males is the standard BB or barred blue morph. All of these morphs are illustrated on this page. Even within a morph, much variation can be seen from one locality to another. The coloration of the dorsal fin is especially variable geographically.
English ecologist Geoffrey Fryer (1956b) recognized this species as distinct from L. fuelleborni during his doctoral research on Lake Nyasa (as it was then known). Fryer named this graceful cichlid L. trewavasae to honor Ethelwynn Trewavas, the taxonomist at the British Museum whose synopsis of Lake Malawi's cichlids a generation earlier (Trewavas, 1935) had considerably advanced the knowledge of their diversity. (The final -ae on the species name signifies that the honoree is female; -i indicates that a male is commemorated.)
Compared with L. fuelleborni, its sister species, L. trewavasae usually is noticeably more slender. This is the easiest way to distinguish the two species, both of which — as already noted — are quite variable in color. There are, however, some significant differences in the ecology of the two species as well.
Whereas populations of L. fuelleborni tend to be found in the upper 5 meters (16 feet) of the water, L. trewavasae has a greater depth range. According to Ribbink et al. (1983), "L. trewavasae favours large rocks, but also occurs in other habitats and is usually fairly evenly distributed from the surface waters down to about 20 m [65 feet]. It has been found to 34 m depth [112 feet]."