First observations on the timing and location of giant kōkopu (Galaxias argenteus) spawning

Abstract

The giant kōkopu, Galaxias argenteus (Gmelin, 1789), is the largest of the galaxiid species and is endemic to New Zealand. While it was the first of the galaxiid species to be described, knowledge of its ecology remains relatively poor, particularly with respect to the reproductive phase of its life-cycle. This article describes the first observations of giant kōkopu spawning sites in the natural environment. A total of nine spawning sites have been discovered across two spawning seasons in an urban stream in Hamilton, New Zealand. Giant kōkopu are confirmed to follow a similar spawning strategy to the other whitebait species. Eggs are deposited in riparian habitats while temporarily submerged by elevated water levels. Eggs then develop terrestrially before hatching when the egg deposition sites are re-inundated during later high flows. This spawning strategy leaves giant kōkopu highly susceptible to flow regime and riparian alterations.