Saving Our Endangered Native Fish

Saving Our Endangered Native Fish
Spawning innovation: The Taharoa fish passage, completed in 2010 is the longest structure of its type in the Southern Hemisphere

T+T welcomes new Fish Passage Guidelines

Tonkin + Taylor’s ecologists and engineers have for many years worked to devise ways of giving our endangered native fish species a fighting chance of survival. This week, we were thrilled to be part of the launch of the New Zealand Fish Passage Guidelines.

Our Hamilton-based water engineer, Bryn Quilter, chairs the New Zealand Fish Passage Advisory Group and was one of some 110 ecologists, engineers, planners, advisory and land management experts who attended the event. He also presented our Conservation Minister, Hon. Eugenie Sage, with a chocolate giant kōkopu – or Galaxias argenteus, a member of the whitebait species - to mark the occasion.  

New Zealand has 77 species of freshwater fish. Fifty-seven of those are indigenous, or unique to this country. Sadly, 41 (72%) of our freshwater species are threatened with, or at risk of, extinction.  In fact, we are losing our native fish at a higher rate than almost anywhere else in the world.

Some have already disappeared from our waters. The grayling, the only New Zealand freshwater fish ever accorded full legal protection, was last seen in 1923. But the law aimed at its protection, passed in 1951 and reaffirmed in 1983, remains in force today.

“Many fish species, including some that used to be widespread, are now absent from many of the streams they used to occupy. Local extinction is often the result of several threats operating together. Native fish have had to contend with habitat loss from wetland drainage, declining water quality, reduced river and stream flows from water abstraction or diversion, loss of spawning sites and barriers to migration,” Ms Sage said.

“Badly designed, sited, constructed and maintained obstacles like dams, weirs and culverts, which block fish and eel movement up and down waterways and between rivers and the sea, are a major threat to freshwater fish.

“Native tuna/eels, are born in the sea near Tonga. Oceanic currents carry these tiny transparent creatures back to New Zealand where they enter river mouths as glass eels. They need to be able to move upstream and find somewhere to live. Eels and many of our whitebait species, which also spend part of their life at sea, are struggling. We can help them thrive by ensuring that in-stream structures don’t obstruct fish passage.

“The national fish passage guidelines, developed by DOC and NIWA with input from the New Zealand Fish Passage Advisory Group, will inform the planning, design, construction, management and monitoring of structures up to 4 metres high in waterways,” Ms Sage said.

Bryn agrees that our “enormous legacy” of problematic infrastructure is not helping the situation. Work done by NIWA collating available culvert data across New Zealand has shown that there are more than 6,000 culverts likely to obstruct fish passage. “That loss of connectivity in our waterways is leading to a decline in the biodiversity of our freshwater species,” he says.

The new guidelines are aimed at preserving and enhancing our native fish populations by allowing them the full use of their natural habitats, while following natural migration and breeding patterns.

Bryn has been working on the issue for nine years, working alongside T+T ecologists, including Dean C. Miller, to develop engineering solutions to allow the safe passage of fish.

“Ecologists use in-stream surveys to establish whether there is an issue, or a particular type of fish that needs passage,” Bryn explains. “I look at how that solution is designed and built.”

“The launch of this guidance is to help frame those solutions because they’ve been applied inconsistently across country for a long time.”

Effectively, that means developing infrastructure in ways that facilitate safe passage for fish, he says: “The new guidelines are different and will be challenging, in that they promote a stream simulation approach, i.e. allowing streams to do what they would do naturally and for us to intervene less.”

The Taharoa Denil fish by-pass and fish ladder was built to allow a wide range of spawning freshwater fish to migrate from the Tasman Sea to Lake Taharoa. Designed by T+T for New Zealand Steel Mining and completed by Spartan Construction in 2010, it is the longest structure of its type in the Southern Hemisphere – and it works.

“From day one fish were observed travelling up the new fish pass into Lake Taharoa and regular monitoring shows good movement of a wide variety of fish species between the lake and the sea,” NZ Steel Mining mechanical supervising engineer, Dave Nicoll, commented soon after the project opened.

T+T’s ecology team has, and will continue to, lead fish science and the protection of endangered freshwater species.

“The new guidelines will provide a definitive resource that our ecologists and engineers can draw on in providing great solutions for our clients,” Bryn says.

The guidelines can be found via DOC, NIWA and MFE websites. Further summaries of the guidelines will be developed in coming months.

See the One News story here.