Petrocephalus catostoma is a small (13 cm or 5 inch SL)
mormyrid, known at
Nkhota Kota, Malawi, as "Ntachi" and called the "Churchill" by
European southern Africans. It is widespread in central and southern
Africa. In his checklist of the fishes of Nyasaland (Malawi),
Jackson (1961)
regarded it as "not uncommon in pools and streams but not from the
main lake." It has since, however, been collected along the lakeshore
proper. FishBase
includes Lake Malawi in the distribution summary, and lists two
lakeshore localities in Mozambique on the occurrences
page for this species: "4 km nord de la baie de Nego, lac Nyassa" and
"Punta Messuli, lac Nyassa."
Skelton (1993) provides a brief summary of
the ecology of this species on floodplains and in the more slowly flowing
parts of rivers, where it congregates in shoals. The diet consists of
small invertebrates including insect larvae. Breeding occurs during the
rainy season; the fishes are suspected of moving upstream to breed.
Skelton remarks, "An unconfirmed report claims the males are territorial
and build a nest."
Petrocephalus catostoma is most similar to
Pollimyrus castelnaui in the
Lake Malawi fauna. However, P. catostoma is the only mormyrid
found in Lake Malawi that has all of the following characteristics
(adapted from Skelton, 1993: 92-93):
Length of dorsal fin base slightly shorter than anal fin base;
Chin without a swelling;
Mouth small and inferior (located below and behind front of head); and
Anterior and posterior nares (nostrils) on each side of head are
close together, separated by less than the diameter of each.
