Biology and ecology of the ubiquitous estuarine clupeid Gilchristella aestuaria from southern Africa.

Abstract

The estuarine roundherring Gilchristella aestuaria is a well-studied southern African endemic fish species. This widespread and abundant clupeid is an important food source for piscivorous fish species and is a major component of the planktonic food web in all types of estuaries on the subcontinent. Although breeding only occurs in estuarine and certain fresh waters, genetic mixing of populations can occur by adults moving along the coast and entering adjacent estuaries. The morphometry of the species can vary considerably, often reflecting contrasting turbidity and trophic conditions pertaining to different estuaries. A wide variety of topics are reviewed, including G. aestuaria distribution, abundance, phylogeography, habitat utilization, gene flow, breeding biology, larval ecology, diet, food consumption, trophic status and predation. In addition, the recent identification of the negative impacts of harmful algal blooms on the larvae and juveniles of this species is noteworthy, particularly as excessive nutrient inputs and eutrophication are becoming an increasing South African and global problem for fishes in estuaries.