Environmental Reporting, Ministry for the Environment and Statistics New Zealand
"Freshwater plant and animal pests can have significant negative impacts on ecosystem health by reducing indigenous biodiversity through predation and competition, and destabilising aquatic habitats. Freshwater plant pests can cause economic losses through blocking water intakes for hydroelectricity generation, impeded drainage or irrigation. In addition, pests can affect the suitability for recreational activities. This dataset relates to the ""Freshwater pests"" measure on the Environmental Indicators, Te taiao Aotearoa website. "
Source: National Institute of Water and Atmospheric Research
Method: "Freshwater pest observations, spanning from pre–1980 to 2013, have been mapped. Maps include observation data from three databases: NIWA’s Freshwater Fish Database, for fish; NIWA’s Freshwater Biodata Information System, for invertebrates and plants; and the Ministry for Primary Industries (MPI)’s Didymo Samples Database, for Didymo.
The information in these databases was supplied by a variety of individuals and institutions. Observations were made using a number of methods including line fishing, electrofishing, nets and traps, snorkelling, diving and spotlighting.
The accuracy of the data source is of medium quality."