Lake Horowhenua (Waipunahau) is of substantial historical, cultural and recreational value to the people of the Horowhenua region. However, water quality and biodiversity within the lake has been in decline for a number of years. As part of lake restoration efforts by Horizons Regional Council and the Lake Horowhenua Trustees, a survey of fish species in Lake Horowhenua was conducted by the University of Waikato using boat electrofishing and fyke netting. A lake restoration plan had previously identified invasive fish species such as koi carp (Cyprinus carpio) and European perch (Perca fluviatilis) as being potential barriers to rehabilitation of the lake. The purpose of this survey was to determine the abundance and diversity of fish species within the lake and to ascertain if pest fish species were present at biomasses high enough to be negatively impacting on lake ecology. Recommendations would then be made as to the potential methods and necessity for pest fish removal.