The "Threespot barb," Barbus trimaculatus, is another small barb
found over a wide area of sub-Saharan Africa, from the upper Congo to
the east coast in Tanzania and south to Natal, South Africa.
In Jackson's (1961) checklist, this species
is assigned only to his "Zone III" (the lower reaches of rivers).
However, it definitely occurs in sheltered near-shore areas of
Lake Malawi proper, as well as in marshes and swamps adjacent to the
lakeshore. Worthington (1933)
reported 21 specimens from Vua, from the southwest arm, and from
Bar House (lower southeast arm). Moreover,
Konings (1990a: 473) includes a photograph
of an individual collected at Kande Island, just offshore along the central
west coast of Lake Malawi.
Live fish taken from clear water are silvery with olive-brown
dorsal surface and three dark spots on the sides. These spots
are usually about the size of the eye but in some specimens
the anterior two may be in the form of an elongated dash.
Specimens taken from muddy water are pallid with the anterior
two spots often missing but these develop after preservation
in formalin solution. Juvenile fish have a dark spot at the
base of the anal fin.
Barbus trimaculatus is insectivorous (FishBase;
Worthington, 1933). Food items identified
in stomachs include caddisfly and mayfly larvae, dragonfly nymphs, adult
water beetles, and the seeds of plants. This barb reaches a length of
15 cm (6 inches) in some parts of its distribution,
but Jackson (1961: 549) notes that it
"[g]rows to about 10 cm. [4 inches] but usually less."
The species summary
at FishBase states that it occurs "... in shallow water near river
outlets or close to swampy areas.... Hardy, commonly occurs in a wide
variety of habitats, especially where there is vegetation....
Breeds in summer, shoals of ripe adults moving upstream in spate
after rain. Females produce as many as 8,000 eggs."
Among the small Barbus
species occurring in or adjacent to Lake Malawi, B. trimaculatus
is the only one with all of the following characteristics
(information from
Jackson, 1961: 595):
Striae (streaks) arranged radially (fanwise) on exposed scale edges.
Last simple (unbranched) dorsal fin ray is an enlarged, bony
spine and is not serrated behind.
Color pattern consists of one to three distinct spots along the side.
B. trimaculatus is most likely to be confused with
B. arcislongae, under which the
features distinguishing the two are given.
The above illustration by Hilda M. Jubb is taken from
Jubb (1967), and is used here
thanks to the generous permission of Mr. A. T. Balkema of
A. A. Balkema
Publishers, Rotterdam.
