The endemic, haplochromine, cichlid species dock of Lake Malawi represents the most diverse
assemblage of fishes of any of the world's freshwater lakes. Of particular interest are the
interspecific relationships that permit so many species to coexist in this unique ecosystem.
We hypothesized that a detailed study of the feeding associations among three sand-dwelling
species, Taeniolethrinops praeorbitalis, Cyrtocara moori [sic; should be
moorii], and Protomelas
annectens, would provide the necessary information needed to determine if these species
are effective in harvesting specific food resources. Taeniolethrinops praeorbitalis
feeds by plunging its snout into the sand, engulfing a mouthful of sand, retaining prey items,
and expelling the sand through its gills. Immediately after T. praeorbitalis plunges
into the sand, other species, including C. moori and P. annectens, move closer
and begin to forage on the invertebrates suspended in the water column by the disturbance of
the substrate or expelled through the gills of T. praeorbitalis. The gap between the
gill rakers of T. praeorbitalis is significantly (P < 0.05) wider than that of the
other two species; the interraker gaps of C. moori and P. annectens are not
significantly (P > 0.05) different from each other. Most P. annectens consumed
small Arthropoda and Cladocera (0.3-0.8 mm), whereas most C. moori and T.
praeorbitalis consumed chironomids (mean prey size = 4.2 mm). Although there was an
association with interraker gap size and prey size when P. annectens and T.
praeorbitalis were compared, this relationship was not present when the stomach contents
and interraker gap of C. moori was contrasted with those of the other two species.
Thus, we concluded that differences in prey size among these three species is [sic] a
function of interraker gap, prey selectivity, and foraging behavior.