Growth, reproduction and population structure of Diplotaxodon limnothrissa in the southeast arm of Lake Malawi

  • Geoffrey Z Kanyerere Department of Ichthyology and Fisheries Science, Rhodes University, PO Box 94, Grahamstown 6140, South Africa<br><br>Current address: Fisheries Research Unit, PO Box 27, Monkey Bay, Malawi
  • Olaf LF Weyl Department of Ichthyology and Fisheries Science, Rhodes University, PO Box 94, Grahamstown 6140, South Africa
  • Anthony J Booth Department of Ichthyology and Fisheries Science, Rhodes University, PO Box 94, Grahamstown 6140, South Africa
Keywords: Cichlidae, length-at-maturity, mortality, Ndunduma, von Bertalanffy growth model

Abstract

Diplotaxodon limnothrissa is a widely distributed species occurring throughout Lake Malawi from the surface to a depth of at least 220m. It is probably the most abundant cichlid in the lake, with biomass estimates of around 87 000t in the pelagic zone alone. The species is exploited commercially in the southern part of the lake but, since its inception, this fishery has never been assessed. Analysis of sectioned sagittal otoliths revealed that D. limnothrissa is a slow-growing and relatively long-lived species, attaining ages in excess of 10 years. Length-at-age was described using the von Bertalanffy growth model, with combined-sex growth described as Lt = 211.21(1 – exp(–0.24(t + 1.36)))mm TL. Females matured at 139mm TL at an estimated age of 3.18 years. Total, natural and fishing mortalities were estimated at 0.63yr–1, 0.38yr–1 and 0.25yr–1 respectively.

African Journal of Aquatic Science 2005, 30(1):37–44
Published
2005-08-03
Section
Articles