Mass mortality of prawn caused by Alexandrium tamarense blooming in a culture pond in Southern Taiwan. In：T.J. Smayda and Y. Shimizu (eds.)

Abstract

Alexandrium tamarense bloomed in one of seven prawn growout ponds, in southern Taiwan in June 1989 causing mass mortality of the grass prawn, Penaeus monodon. The cell numbers were about 10,000/ml, with a PSP toxicity of 0.72 X 10-4 MU/cell. Abiotic and biotic parameters of the pond water were compared. High concentrations of ammonia-N, abundance of a ciliate (tintinnid) and the presence of green algae and diatoms were observed in the pond waters without A. tamarense. A combination of high temperature, low salinity, low ammonia-N, lack of competition with other phytoplankton species, and absence of predators appear to enhance the blooming of A. tamarense. Prawn or fish were poisoned when immersed into the pond water with A. tamarense, or even only to its filtrate. After a certain time, they eventually died, but could recover if removed just before succumbing and placed into strongly aerated, fresh seawater.