Fish recruitment into a South African temporarily open/closed temperate estuary during three different hydrological mouth phases

Abstract

Quantitative recruitment of ichthyofauna into a South African temporarily open/closed estuary (TOCE) was investigated during three distinct hydrological phases: closed overwash, open outflow and tidal mouth conditions. Maximum recruitment densities occurred during outflow conditions and declined when the system became tidally inundated. Recruitment densities were lowest during overwash events. Selective diel variation was evident, with higher night-time densities for each phase. This study highlights the importance of seasonal timing and duration of open conditions and overwash events for structuring ichthyofaunal community composition of southern African TOCEs.

Keywords: breach, ichthyofauna, ICOLL, Mpekweni Estuary, outflow, overwash, species composition, tidal conditions