A boat electrofishing survey of Lake Arapuni was conducted on 2 February 2017 by the University of Waikato to investigate anecdotal reports of koi carp (Cyprinus carpio) presence in the lake. Nine 10-minute electrofishing transects were conducted around the littoral zone of the lake. This resulted in a total distance fished of 3.35 km and a total area fished of 1.34 ha. A total of 100 fish were captured, comprising three species: brown bullhead catfish (Ameiurus nebu/osus), goldfish {Carassius auratus) and rudd {Scardinius erythrophthalmus); in addition, eels (Anguilla sp.) were observed but not captured. Total captured fish biomass was 14.8 kg {11. 7 kg/ha) with goldfish being the most abundant species (86 individuals), accounting for most of the biomass (86.8%). Rudd were the next most abundant species with nine individuals captured (1.0 kg/ha) followed by catfish (five individuals; 0.4 kg/ha). Rudd and catfish boat electrofishing biomass estimates should be regarded as minimal as capture rates for benthic species (catfish) and juveniles (rudd) are often lower than those of adult pelagic species. The reduced capture efficiency of benthic species is due to their preference for depths beyond the extent of the electrofishing field (approximately 2 m in extent from the anode), in addition benthic species are more likely to be missed by netters due to their reduced visibility. The smaller size (<100 mm FL) of juvenile fish makes them less susceptible to the electric field and therefore less likely to be captured in numbers representative of the community composition. No koi carp were captured even though the area fished was typical of their preferred habitat. While the presence of koi carp in Lake Arapuni cannot be completely discounted, the survey results indicate that they are either absent from the lake or present in low numbers. Furthermore, the goldfish population was dominated by large adults (>150 mm FL), many of which were highly coloured and had markings similar to those of koi carp. It is likely that these larger coloured goldfish were mistaken for koi carp in previous sightings, especially as adult goldfish form small aggregations similar to those of koi carp. If koi carp are present in Lake Arapuni they are likely to be at biomass levels too low to mount viable control or eradication programmes given the large area and depth of the lake.