Abstract:
Aspects of the ecology and biology of the Lowveld largescale yellowfish (Labeobarbus
marequensis) were studied in the Luvuvhu River over a period of three years.
In this study the origin of the species, its phylogenetic relation to the other South African
yellowfish species, its distribution and gross morphology are discussed and the lack of
knowledge regarding aspects of the species is pointed out. The study area is identified and its
geology, hydrology, climate and water quality as well as the historic distribution of the
species is discussed.
Adapted “truss” techniques were applied to measure and calculate the morphometric features
related to feeding and habitat preference of the species. From this data the habitat preferences
and requirements were inferred after which it was compared to data obtained during field
surveys. The study of the breeding biology and ecology of the species included investigations
of gonad and egg structure and development as well as seasonal surveys of selected breeding
sites. The diet of the species was established through stomach content analyses and related to
the digestive tract morphology. Data obtained from the Xikundu fishway was used to
establish the migratory behaviour.
Results show that nine distinct stanzas or growth phases, each with its own morphometric
characteristics, were identified. The body form, and some morphological aspects, of the
species make it suitable to cope with flowing water. Ontogenetic changes in body form and
the identified morphological aspects were observed and related to the habitat preferences of
the stanzas. A distinct ontogenetic shift in preferred habitat was illustrated. The species was
shown to be fractional spawner with two spawning events per annum. A major extended
spawning event occurred during spring or early summer and coincided with a temperature
increase and in particular with an increase in flow. Breeding occurred at sites with fast
flowing water over cobble or boulder beds and it was observed that the presence of nursery
areas related to breeding biotopes was extremely important. Although the diet of the species
was dominated by plant and algal matter, juvenile stanzas ingested large amounts of animal
material. It was found that the spatial movements of the species could be characterised as
migrations and that breeding and dispersal migrations occurred.
