Reproductive and feeding biology of the endangered fiery redfin, Pseudobarbus phlegethon (Barnard 1938) (Teleostei: Cyprinidae), in the Noordhoeks River, South Africa

Abstract

The aim of this study was to contribute to the knowledge on the reproductive and feeding biology of the endangered Pseudobarbus phlegethon (Barnard 1938) in the Olifants River system, by providing estimates of its maturity, reproductive periodicity and the diet in the Noordhoeks River. The study was based on available specimens, stored in the fish collection of the South African Institute for Aquatic Biodiversity, that were collected by electrofishing between March 1996 and July 2005. A total of 158 fish were examined. The sex ratio was 1:1. Maturity was validated histologically. The length at first maturity was 33.2mm SL for males and 35.5mm SL for females. Gonadosomatic index and the proportion of ripe fish indicated a spawning peak in October. The ratio between gut length and fork length was consistent with carnivorous cyprinid species. Foregut contents were dominated by invertebrate remains (frequency of occurrence (FO) = 75%), but also contained filamentous algae (FO = 54%), sand (FO = 53%) and detritus (FO = 45%). The number of invertebrate prey found in the foregut ranged from 0.3 ± 0.6 (mean ± standard deviation) in May 1998 to 33 ± 21.5 in October 1998. The invertebrate prey was predominantly aquatic and the family Chironomidae was most important, contributing >80% to the index of relative importance in most months. The significance of these results is discussed with regard to the conservation of this species.