Rare native fish population boom
Archived content: This media release was accurate on the date of publication.
IntroductionA small spring-fed tributary of Fraser Stream near Twizel has had a large increase in two of New Zealand’s rarest native fish species, attributed to the introduction of a trout barrier.
Date: 20 December 2010
A small spring-fed tributary of Fraser Stream near Twizel has had a large increase in two of New Zealand’s rarest native fish species, attributed to the introduction of a trout barrier.
At the last monitoring visit by Department of Conservation staff, 99 lowland longjaw galaxias (Galaxias cobitinis) and 228 bignose galaxias (Galaxias macronasus) were caught in two monitoring sites in the stream. Additionally, large numbers of juvenile fish were seen indicating that good spawning has taken place.
"Given bignose galaxias were only discovered as a new species nine years ago, these recent findings are extremely positive for their survival," says Dean Nelson, DOC Biodiversity Manager.
“Both lowland longjaw galaxias and bignose galaxias are far smaller than introduced rainbow trout and brown trout, making our native fish very vulnerable.
“These galaxias are often hard to spot even though they may be present in a stream – they tend to hide in cover or quickly disappear. The trout barrier has been in place now for two spawning seasons and we are starting to see results.”
Another threat these fish face in the introduction of didymo. The popular Dusky Trail track runs parallel to Fraser Stream which is in Ruataniwha Conservation Park. Cyclists and walkers who do the Dusky Trail are encouraged to travel in a clockwise direction, crossing Fraser Stream first and Twizel River last to help keep didymo out of Fraser Stream.
“It is extremely fortunate we have managed to keep both didymo and trout out of Fraser Stream and its tributaries. The public are left with a very important site which is ultimately providing a haven for two of our rarest native fish,” said Dean Nelson.