AQUATIC SPECIES/ No effect on the hatching success or egg development rate of four marine fish species - red seabream (Pagrus major), black porgy (Acanthopagrus schlegeli), striped knifefish (Oplegnathus fasciatus), and threeline grunt (Parapristipoma trilineatum) - was observed at kaolinite concentrations up to 10 g/L for 24 hr. Larvae were more sensitive to kaolinite: the 12-hr LC50 values were 170 and 710 mg/L for P. trilineatum and O. fasciatus, respectively; mortality was also observed for P. major at concentrations of 1000 mg/L and above.