Spawning of riverbream, <i>Acanthopagrus berda</i>, in Kosi estuary

Abstract

The spawning habits of Acanthopagrus berda, an estuary-dependent seabream (Family Sparidae), are investigated. Spawning takes place in the Kosi estuary at night and eggs are transported out to sea during peak ebb tides. There is a preponderance of males in the spawning aggregation (sex ratio — 8,8 :1 m/f) and indirect evidence suggests that males and females are continually recruiting to the aggregation, spawning, and moving back up into the lakes so that there are no more than 2000 individuals at the mouth at any one time. Sexed fish were tagged in an effort to produce evidence of protandrous sex change in this species. It is noted that the degradation of estuarine habitats could have serious effects on an estuarine-dependent species which has developed a spawning strategy of this nature.