Habitat Related Differences in Growth and Condition of New Zealand Koi Carp (Cyprinus carpio).
Centre for Biological and Ecological Research. Department of Biological Sciences. University of Waikato, Private Bag 3105, Hamilton. New Zealand.
Email: gwt2@waikato.ac.nz
Feral koi carp populations (Cyprinus carpio) were first reported in the Whangamarino wetlands in the early 1980s. Koi carp are now abundant in the lower Waikato River and several neighbouring lakes and wetlands. In addition, self-sustaining populations have been reported in numerous isolated locations throughout the North Island and the north of the South Island.
Despite their proliferation through some New Zealand waterways, research on New Zealand koi carp has been limited. As an initial step towards gaining a greater understanding of koi population dynamics and ecology, and to obtain data relevant to future management strategies, the condition of a number of koi populations was assessed using condition indices calibrated from historical length-weight data. Fish were sampled from both lakes and rivers in the Waikato region.
Both male and female riverine fish were significantly greater in both total condition and somatic condition than fish from Waikato lake populations. Furthermore, analyses of fish growth rates from each population indicated a trend to higher growth rates in riverine fish compared to lacustrine fish. This suggests that differences in habitat type have an impact on koi condition and growth, and may indicate that lake populations are resource limited or have reached carrying capacity. These data imply that ecological impacts of koi are greater in Waikato lakes than rivers.
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