Abundance, behaviour and habitat requirements of the banded kokopu Galaxias fasciatus Gray (Pisces: Galaxiidae)

The native freshwater banded kokopu (Galaxias fasciatus Gray) is generally regarded as a nocturnal predator of small native forest streams. Current methods for determining absolute abundances of this species in these streams is usually by the expensive, labour intensive, and invasive method of electric fishing. Spotlighting at night has previously been used to determine their presence and relative abundance, although the proportion seen (the bias of the method) was unknown. This bias was quantified by determining the numbers of banded kokopu seen at night in 20 m reaches against population estimates made in the same reaches the following day by removal electric fishing. This showed that, on average, only around 64% of fish of all sizes were being seen. Counts made by spotlighting therefore should be multiplied by 1.57 to correct for this bias and to estimate for the actual number of fish present. Spotlighting was found to be less efficient for smaller fish (approximately