Pest fish survey of Hokowhitu (Centennial) Lagoon, Palmerston North

The koi carp is an ornamental strain of the common carp which is believed to be one of the most ecologically detrimental of all freshwater invasive fish species. Numerous “koi carp” sightings have been made by the public in the Holowhitu Lagoon, Palmerston North. Because koi carp is designated an unwanted organism under the Biosecurity Act, the Department of Conservation commissioned a survey be undertaken to determine whether koi carp were present in the lagoon. Due to the abundance of aquatic birds and the public nature of the lagoon, nets were unable to be set and thus the use of an electric fishing boat from the University of Waikato was required. This method provided a non-lethal, quantifiable, method of collecting freshwater fish species in a non-wadeable freshwater habitat. The boat operated by supplying a pulsed DC current into the water column where it attracts and then incapacitates fish, allowing operators to remove them from the water with hand nets