The fish-killing heterotrophic dinoflagellate species Pfiesteria piscicida and P. shumwayae (also Pseudopfiesteria shumwayae) were present throughout New Zealand and were residents of Tasman Bay?s well-flushed estuaries and Canterbury?s brackish lakes, as determined by polymerase chain reaction-based detection assays. The two species occurred in a wide range of salinities and temperatures, although detection was restricted seasonally from spring through to autumn, except for one incidence in the shallow waters of Wairewa/ Lake Forsyth, Canterbury, in the winter of 2003. The DNA sequencing data indicated that P. shumwayae may encompass a suite of genetically closely related species. The presence of Pfiesteria in New Zealand is not considered an immediate risk to fish or human health given the current low-to-moderate nutrient concentrations in New Zealand?s estuaries and brackish lakes. However, increases in nutrient loadings could pose a risk, as has occurred in eastern United States estuaries.
