Indigenous vegetation type and the distribution of shortjawed kokopu, Galaxias postvectis (Teleostei: Galaxiidae), in New Zealand

Abstract

The shortjawed kokopu is found almost exclusively in forested catchments throughout New Zealand. Forest composition appears to be important: the species is found particularly in podocarp/hard‐wood forests, quite often in podocarp/hardwood/ beech associations, but only very rarely in pure beech forest. Sites where shortjawed kokopu are more abundant are always in podocarp/hardwood forest streams. Analysis of distribution in two representative West Coast river systems, the Buller and Grey, shows that there are numerous sampled streams in beech forest catchments within easy reach of shortjawed kokopu migrating upstream from the sea. The shortjawed kokopu is widely present on the West Coast within the “beech gap”, an area between 42°30’ and 43°30'S, from where it is believed that all vegetation was extirpated during Pleistocene glaciations. This area is now forested by podocarp/ hardwood associations because beech forest (Nothofagus spp.) has, as yet, been unable to reinvade. Reasons for this preference for podocarp/ hardwood forest streams are not known but may relate to dietary factors or the need for cover.

Key words:

• Galaxias postvectis
• shortjawed kokopu
• beech gap
• Nothofagus
• podocarps
• distribution
• New Zealand