Science Centres: Aquatic Biodiversity and Biosecurity

Signals from electronic tags implanted in kokopu are picked up by aerials, allowing fish movements to be tracked automatically.

Knowledge of movements of native fish, and their habitat preferences, is essential for river management, especially protection and restoration of biodiversity. At NIWA, we’re using high-tech science to study these secretive animals.

In February, 100 adult banded kokopu (Galaxias fasciatus) and 52 giant kokopu (Galaxias argenteus; both members of the native whitebait family known as galaxiids) were captured from a small tributary in the Hakarimata Range, Waikato, and tagged with tiny electronic transmitters. Each transmitter has an individual number, which is picked up by a series of aerials placed within the stream, and the identity of the fish recorded, along with the date and time, in a data-logger. ‘This is the first large-scale study using electronic tags in a New Zealand stream,’ says fisheries scientist Dr Cindy Baker, who is leading the FRST-funded study.

Anecdotal reports of giant kokopu captures within the Waikato River during autumn/winter suggest that they may migrate down-river to spawn, an idea the study is testing.

Preliminary results show that both banded and giant kokopu are regularly changing pools within the stream and some fish even move out of the stream. This has important implications for conservation of this species and for stream management. In particular, it means that we have to think about spawning movements of kokopu when considering the effects of man-made barriers on native fish, says Dr Baker.