In rare, good news for a tiny Canterbury fish clinging to survival, DOC rangers have discovered a new population of the fish and created an 'insurance' population.
Lowland longjaw galaxias (Waitaki River) are Threatened – Nationally Critical and found only in the Waitaki River catchment. In the past 20 years at least three known populations of the fish have disappeared.
DOC Principal Ranger Dean Nelson says lowland longjaw galaxias, affectionately known as 'jaws', are a low key but intriguing species with a distinctive underbite (hence 'longjaw'), a pencil-thin body and a liking for cool streams and springs associated with braided rivers.
"It's amazing that Waitaki longjaws have survived at all, but they really need our help in the face of multiple pressures, otherwise we're likely to see more extinctions of their populations."
Threats to Waitaki longjaws include predation and competition from trout, invasive aquatic weeds that ruin their habitat, habitat loss and climate change. Trout exclusion barriers are in place to protect most of the populations, but trout can get past the barriers when they are overtopped in flood conditions and reach longjaw populations.
"We were over the moon when eDNA tests revealed a previously unknown sub-population of Waitaki longjaws in the Maryburn Conservation Area in a recent survey. We followed up with some fishing to get material evidence of the fish and with great celebration, we found 22 of them in a small section of the stream."
Dean says having an insurance population in a relatively safe area is crucial to longjaws' survival.
"The beauty of the new find is that we were able to take 10 longjaws from the Maryburn site and move them to safe stream, along with 20 jaws from a population at Fraser Stream to create an additional population."
In 2025, DOC created the new longjaw site by constructing a trout exclusion barrier at Waterwheel Wetland, which is on public conservation land and free of trout and problem weeds. The site also protects a similar species called bignose galaxias and the two species are known to happily co-exist in other sites.
"Effectively, we now have two new populations, giving us a total of nine longjaw sites. This helps spread the risk of losing the species to a catastrophic event and improves Waitaki longjaws' overall security.
"However, we continue to be on the lookout for other trout-free translocation sites as we work to ensure the resilience and secure the future of this special fish."
Dean says although Waitaki longjaws live in pretty remote locations, there are naturing actions for people wanting to help the species.
"Waitaki longjaws aren't well known in the world of New Zealand's iconic galaxiids so telling people about these amazing little fish makes a difference.
"For those that live or work in the catchment, protecting springs and side channels, managing invasive aquatic weeds, and limiting stock access can help improve Waitaki longjaws' prospects."
Background
Lowland longjaw galaxias have two closely related populations that only live in small streams and spring-fed tributaries of the upper Waitaki River and Kakanui River systems in North Otago.
The few remaining populations are in the Kauru and Kakanui rivers in North Otago, and in a handful of spring-fed streams in the Mackenzie Basin. The lowland longjaw galaxias found in the Kauru and Waitaki catchments are genetically distinct from each other.
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