Giant kokopu is one of the rarer species that make up part of a whitebait run. Image: Mike Joy, Massey University
Most New Zealanders are aware of the annual spring migration of swarms of tiny fish known as whitebait. In most river systems, the dominant species is inanga, but a whitebait run is made up of the juveniles of five species of galaxiid fish, including banded kokopu and koaro, and the rarer giant kokopu and shortjaw kokopu (pictured below, image courtesy of Alton Perrie), which are threatened with extinction. The migration marks their return from several months at sea.
Andy Hicks is a PhD student with Gerry Closs at the University of Otago, where he studies the recruitment of whitebait in rivers throughout the country. The group found that not all whitebait species need a marine environment for larval development, but instead remain in freshwater, migrating between rivers and lakes. Using the ear stone, or otilith, Andy Hicks was able to trace the movement of different whitebait species and assess the quality of their habitat.
To find out more about the distribution of large galaxiids (four of the five whitebait species) have a look at research by Mike Joy and his students at Massey University or at NIWA's freshwater fish atlas.