Consistent timing of juvenile fish recruitment to seagrass beds within two Sydney estuaries

Abstract

Recruitment patterns of juvenile Rhabdosargus sarba (Sparidae) and Pelates sexlineatus (Terapontidae) were examined by frequent (1–4 weeks) beach seining of seagrass beds in Sydney, south-east Australia. Two sites within each of two estuaries (Botany Bay and Pitt Water) were sampled for one year. One site within Botany Bay was sampled for 3 years. A total of 12 824 juveniles of R. sarba and 7037 juveniles of P. sexlineatus were collected. R. sarba recruited in 4 pulses during winter/spring, while P. sexlineatus recruited in 6 pulses during summer/autumn, and the timing of recruitment events was consistent among locations and years. P. sexlineatus recruitment coincided with new moons, but R. sarba recruitment dates were less precisely determined. Predictable annual recruitment patterns result in temporal partitioning of seagrass habitat between these two abundant estuarine species. Spatial differences in magnitude of recruitment events among sites reflected patterns of estuarine circulation.