The fish‐killing heterotrophic dino‐flagellate 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 s...