Watercare gives migrating fish and eels a helping hand

31 October 2018


Every year Watercare staff give native fish and eels a helping hand with their migration journey.
 
Fish traps are placed at the bottom of dam spillways at some of our dams in the Waitākere and Hūnua ranges and in streams to catch elvers (juvenile eels) and galaxiids (whitebait). The tiny fish are then scooped into buckets and carried to neighbouring dams to be released, where they will feed and grow, to continue the lifecycle in a protected environment.
 
Watercare water quality and environmental scientist Matthew Hubrick is part of the environmental assets team who performs the fish transfer operation: “The fish are tiny – only five centimetres long or less and have travelled all the way from the ocean, up rivers and creeks to try to reach the dams.
 
"Our native fish are in real need of protection as their numbers dwindle. The transfer operation is a very important and satisfying part of our work.”

Watercare dam technician, Gareth Whittington releases native whitebait and juvenile eels into Lower Nihotupu Dam.
Watercare dam technician Gareth Whittington releases native whitebait and juvenile eels into Lower Nihotupu Dam.
 
Staff visit the fish traps two to three times per week. Over a season, up to 10,000 fish can be transferred to the dams. Each bucket-load of fish is photographed and the numbers are recorded and sent to the Ministry of Primary Industries and Auckland Council.

Whitebait tend to form shoals within seconds of swimming away from their bucket. Elvers begin burrowing into mud straight away, out of sight of kotuku (white heron) and other potential predators. Native eels typically live 15-30 years, although some spectacular specimens are thought to be 80 years old.  
 
In the autumn, the environmental assets team focuses on catching adult shortfin and longfin eels, using un-baited nets. They are released downstream, so they can find their way to the sea to breed. 

Watercare staff are trained to identify morphological changes which indicate eels are mature and ready to migrate, e.g. changing eye colour.  Details such as weight and length are recorded. Eels that aren’t ready to migrate are returned to the dam.
 
Fishing has had a significant impact on both native eel and whitebait numbers, so much so that in April this year, the Aoraki Conservation Board warned government departments that within 16 years, New Zealand whitebait could be wiped out.
 
Our dams offer a special haven to native species as the dams are located within protected catchments surrounded by native bush and fishing is banned.
 

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