Environmental cues for koi carp (Cyprinus carpio) spawning aggregations and bottleneck locations near Huntly, New Zealand

Abstract

Koi carp (Cyprinus carpio) were monitored from August to December 2014 near Huntly, in the north Waikato, to document migratory and spawning behaviour. Monitoring involved a combination of daily water level and temperature logging, as well as semi-weekly observations of koi carp numbers and spawning activity. These data were used to examine the influence of water level and temperature on migration and spawning behaviour. No correlation between water level and koi carp migration was found; however, the monitoring period followed two years of drought in the region resulting in unusually low water levels for the time of year. In contrast, koi carp migration and spawning behaviour appeared to be related to water temperature, with spawning consistently observed after water temperatures were stable at 15°C. This temperature spawning threshold is lower than previously observed for northern New Zealand, but is within the range identified in overseas literature. It is recommended that future studies investigate a greater range of seasonal and climatic variations, and address the potential for increased activity at night when fish may be more active.