At 32mm the little galaxiid is just beyond the whitebait stage. Its presence though, 600m up from the Waitakere River past the multiple cascades and waterfalls of a rock bottomed, forest-shaded stream at Matuku Link, shows the determination and climbing ability of banded kokopu. A mere 2 months ago it came out of the Tasman Sea following the Waitakere river for some 4-5 km through open river and the te Henga wetland seeking a clear flowing stream to call home. Its timing was fortunate as the flood of the century had just occurred, evidenced still by the log falls across the stream and flattened nikau on the banks. Koura were obviously affected by the flood as their number was far less than on a previous survey while sleek long finned tuna seemed to have weathered the storm, one in each quiet pool. Another interesting find was several Dolomedes, a semi aquatic species of spider. Returning to our vehicles we enjoyed the combined frog and ruru chorus.
Our night time survey of banded kokopu [BK] led by Lyn Hamilton-Hunter was to determine if recruitment of these galaxiids was occurring as a population of Perch in the river, the unfortunate legacy of a misguided coarse fisherman, puts native freshwater fish at risk. Earlier in the evening we had already found several adolescent and breeding-age BK and with their size range of 112 -165mm this already meant different years of inhabiting the stream. Seeing very small juveniles however, absolutely nailed it.
The survey, though useful in itself, was part of a scoping to see if we could translocate Giant Kokopu [GK] into our streams from the breeding facility where Lyn is employed. If BK, their galaxiid cousins could make it past various hazards and predators, then so could GK as all come from the sea in the mixed species schools we call whitebait. So because of BK we might be OK for GK!
John Sumich – Matuku Link trustee – reporting on the freshwater fish survey done on 21st November 2021
Top row: Dolomedes semi aquatic spider – biggest Giant Kokopu in hand – biggest Giant Kokopu – smallest Giant Kokopu. Bottom row: young yellowish tuna (eel)