Hicks, B.J., Bell, D.G., Ring, C.A. & Tempero, G.W. (2004). Boat electrofishing survey of Apata Pond and Lake McLaren. CBER Contract Report No. 33, client report prepared for the Department of Conservation, Bay of Plenty Conservancy, and Environment Bay of Plenty. Hamilton, New Zealand: Centre for Biodiversity and Ecology Research, Department of Biological Sciences, The University of Waikato.
Abstract
We used New Zealand’s first successful electrofishing boat to catch koi carp (Cyprinus carpio haemaotopterus; Zhou et al. 2003) and rudd (Scardinius erythophthalmus) at two sites in the Bay of Plenty, North Island, New Zealand. Five large koi carp were caught in a pond near Apata; shortfinned eels and adult inanga were also caught. In Lake McLaren, a small hydro-electric impoundment on the Wairoa River, two rudd were caught; longfinned eels (Anguilla dieffenbachii), common bullies (Gobiomorphus cotidianus), and brown and rainbow trout (Salmo trutta and Oncorhynchus mykiss) were also caught.
Low ambient conductivities (43-90 µS cm⁻¹) is likely to have restricted the electrofishing field and power transfer to the fish, but fish capture was still successful. Clear water compensated somewhat for the reduced effectiveness of the field.
Fish densities were low at both locations. The minimum fish density was 0.31 fish 100 m⁻² in the pond at Apata, and 0.61 fish 100 m⁻² in Lake McLaren. These should be regarded as minimal densities because only a single pass was conducted. All the koi carp caught in the pond at Apata were 521 to 564 mm fork length and all were 8 years old; there were two males and three females. One female was about to spawn; however, no other koi carp were found, so breeding appears to have been unsuccessful in this habitat. The two rudd from Lake McLaren were 203 and 240 mm fork length 6 and 7 years old respectively. Thought no younger age classes were caught, we cannot exclude the possibility that rudd could reproduce successfully in Lake McLaren.
