New Zealand’s iconic whitebait species are disappearing from our waterways, but help could soon be at hand for the threatened giant kōkopu. Scientists are carrying out a trial involving ‘tagging’ of individual farm raised fish as part of a plan to reintroduce them to our waterways.
The National Institute of Water and Atmospheric Research (NIWA) and Mahurangi Technical Institute (MTI), who will be providing the fish, have been engaged by the NZ Transport Agency and its Northern Gateway Alliance (NGA) partners to undertake a project as part of the mitigation programme associated with the recent construction of the Agency’s SH1 toll road. Together they aim to repopulate a stream in Orewa with giant kÍkopu. The giant kÍkopu is one of five galaxiid fish species which, in their juvenile form, make up the whitebait catch and is classified by the Department of Conservation as nationally vulnerable.
It is thought that giant kōkopu were once common in the Nukumea Stream in Orewa, but they have been in decline for a long time and the last recorded sighting was in 2002. It is hoped that the re-introduction of young adult giant kōkopu will help re-establish a self-sustaining population in the stream.
NIWA has implanted the giant kōkopu with tiny transponder tags (PIT tags). Each tag has a unique ID, so when the tagged fish are introduced to the stream they’ll be able to identify each fish separately as they pass by the antennae positioned in the stream. Dr Paul Franklin (NIWA) says “This is the first controlled trial in New Zealand testing whether native æish can be successfully stocked into a stream. By tagging the fish we are able to monitor how well they survive and where they choose to live.
The fish which are to be used for the trial have been hatched and reared in tanks at MTI from eggs originally collected from the Waitetuna River. David Cooper, Special Project Manager at MTI, says “The production and provision of these fish form a part of MTI’s wider breeding activities with New Zealand native fish and although the majority of these currently go to the ornamental fish industry it is our hope to support more and more conservation projects like this in future.
In the initial trial, around thirty adult giant kōkopu will be released into the stream. They will be monitored by NIWA and a team led by Dave Slaven, Ecology Team Leader NGA, to see if the translocated fish survive and breed and whether there is any impact on the fish and aquatic insects which already live in the stream.
Adult giant kōkopu breed in freshwater. Their larvae drift out to sea and then return to rivers and streams as one of the species that make up the famed New Zealand whitebait we enjoy as a delicacy. A major cause of their decline has been loss of habitat. Scientists also think that the adult fish produce a chemical signal or ‘pheromone™ to telì whitebait which streams to return to. This study hopes to establish whether native fish re-introduced to a stream with suitable habitat will survive, breed, and provide the necessary chemical signals to encourage juveniles to return.
If the trial is successful, the Transport Agency and its NGA partners plan to release 500 –1000 juvenile giant kōkopu into the stream at a future date to augment the declining population.
The giant kōkopu were sourced from a whitebait farm at the mouth of the Waitetuna River which flows from the Pirongia Mountain through the farmlands of the Ngaati Mahanga, and others, to the Whaingaroa Harbour (Raglan Harbour).
Nga Rima o Kaipara (Ngati Whaatua) have been involved in the project and will be blessing the release of the giant kōkopu.
Press Release: NIWA