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Changing the current: Fish passage in Aotearoa

Changing the current: Fish passage in Aotearoa

Many of our fish species are diadromous, which means they must move between salt and fresh water to complete their lifecycle. This includes some species which climb their way to different parts of a catchment. For example, banded kōkopu have been known to climb up steep 20-metre waterfalls to reach their destination! Over time streams have been diverted or piped and barriers like dams, weirs and culverts have been created in our water ways, restricting this vital movement. In fact, 95% of Wellington streams are now piped and sometimes even just a small lip on a pipe means small fish can’t finish their journey.  

Fish movement is vital for several reasons, including ensuring species suvive. Fish need to get to and from the ocean to breed and if they can’t, the species will eventually become extinct. Even if some fish can make it, the overall population will continue to decline over time. This is being seen in species, including tuna/eels.  

Fish movement is also important to maintain genetic diversity. Just like you might feel the need to move away from your hometown as a teenager to get a fresh start, if fish have to stick in the same part of a stream, things get stale fast. There will be limited resources available, and fish may begin to inbreed, resulting in an unhealthy population.   

If the fish are all in one spot, they also miss out in being involved in the wider food web, eating smaller fish and invertebrates and being kai for other species. It also means nutrients don’t get filtered up or down the system. Simply put, the balance and the mouri/lifeforce of the system is skewed.   

At Zealandia Te Māra a Tāne, we are focussing on whole ecosystem restoration, which means restoring the environment in such a way that allows these natural processes to occur. We are also looking beyond our fence, further downstream. Zealandia Te Māra a Tāne is leading the Kia Mouriora te Kaiwharawhara/Sanctuary to Sea kaupapa/project which is a collaborative whole-of-catchment restoration initiative with a 100-year vision that the mouri of the Kaiwharawhara is healed. We can’t restore the water in the sanctuary in isolation, as it travels down the catchment where it faces many other pressures including fish barriers.   

While fish barriers are hard to change on an individual level, one action you can take is to get to know your local stream. Find out where it runs – is it piped or open? Does it need a hand?  

Planting alongside the water, collecting rubbish or speaking to your local council about the issues your stream faces are all actions you can take to help the awa/stream/river. Sometimes the simple act of reconnecting with your wai/waterways is the biggest action you can take. We can’t care for something if we don’t even know it exists.    

Photo credit: Andy Macdonald. 


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