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  • Our cities have a maze of often forgotten waterways tucked away beneath weedy banks or buried in concrete pipes under busy streets. Native freshwater fish, our hidden treasures, may still be surviving – but only just.

    Presently the most polluted waterways in New Zealand are found in urban areas.

    What are some of the biggest barriers to stream and native fish health in our urban areas and what can we do to help?

    They’re streams – not drains!

    In the past, we’ve treated urban streams like drains – straightening them, channelling them and piping them to make them carry away rain and wastewater as quickly as possible – yet urban waterways often have significant areas of native riparian or wetland vegetation that provide habitat for native plants and animals.

    They are also an important network that provide corridors for birds, insects and fish to move around in, to seek food or shelter or to carry out their life cycle.

    City streams can also be valuable recreational assets that soften the urban landscape and provide green spaces for people to relax in.

    Some of our urban waterways contain heritage sites of historical and cultural importance, which makes a lot of sense when you remember that we all need water and our ancestors would often build their homes or developments around waterways.

    Papakāinga Ihumātao at the Otuataua Stonefields Historic Reserve is an example of an important heritage site located by urban waterways. Manukau Harbour and the Oruarangi Awa were sources of food for this papakāinga. Learn about the impacts of humans on this environment and the work of kaitiaki and local students to restore the area in Ihumātao – past and present.

    Stressed-out city streams

    Urban streams are usually in worse condition than rural streams for every water quality measure – clarity, nutrients, temperature, bacteria and heavy metals. This leads to low abundance of aquatic species and poor biodiversity.

    In cities, our fish encounter a bewildering tangle of pipes, culverts, channels and drains with overheated, murky and polluted water. These streams block their ability to move around and to migrate to complete their life cycle.

    Streams and fish habitats are also being lost every day to urban development, particularly small streams high in the catchment. In Auckland, 11 kilometres of streams are piped every year.

    If having your home completely destroyed is not enough to deal with, native fish are also facing other issues caused by humans in their environment:

    • Fish living in urban streams are doused with harmful substances washed off our roofs, streets and building sites every time it rains.
    • Concrete slurry, paint, food scraps, oil, fuel, mould killer, heavy metals, car cleaners, weed sprays and soil carried in stormwater can poison, burn, blind or suffocate fish.
    • Animal poo from ducks, pigeons, pets and others can contaminate water with harmful microbes.
    • Heavy downpours on hard surfaces like roads, roofs, driveways and car parks send large pulses of water down streams, eroding banks, transporting mud and rubbish and sometimes causing sewer overflows.

    So what can we do to better the chances of survival for our urban-dwelling native fish?

    Breathing life back into urban streams

    There is an increasing interest in urban stream restoration and stormwater channel development. Even if you don’t live by a stream, there will be a network of underground pipes connecting your home to the closest stream. Some of you may be lucky enough to live beside a stream or river. Either way, there is lots that you can do to keep streams healthy.

    Learn more about how we can help our local streams and native fish in Stream works for fish, Healthy farms, healthy fish and Planning for change.

    Case study: Oruarangi Stream

    A devastating industrial dye spill in Auckland poisoned a stream, killing freshwater and marine life. Local students teamed up with kaitiaki and scientists to help restore the mauri to the Oruarangi Stream. The work to restore the stream began with the gathering of baseline data including species counts and water quality testing. The timeline River investigations and the nature of science documents the different stages of the project.

    Related content

    The Connected article The fish highway covers a scientist's discovery that native fish and tuna were using Wellington’s stormwater system as access between streams and the sea.

    Activity ideas

    The Hub has a number of activities for students to explore water quality and water contamination:

    Professional learning development around water and pollution

    Watch these PLD recorded webinars Exploring water pollution and Exploring groundwater and pollution.

    The videos Building an aquifer model, Non-point source contamination and Point source contamination provide step-by-step demonstrations of how to build an aquifer model and conduct the groundwater pollution activities. By viewing the videos first, teachers gain a better understanding of how to carry out the activities in the classroom.

    To understand water pollution often begins with an understanding of the water cycle. Learn about the water cycle.

    Useful links

    Recent statistics

    Read the latest statistics on the state of our freshwater from the Ministry for the Environment and Stats NZ in Our freshwater 2020.

    Want to know more?

    Learn more about running a stream protection project from the Department of Conservation.

    Contact your local or regional council for advice on improving water quality and conducting stream restoration, some examples below:

    Urban stream restoration groups


    This resource has been adapted from the Hooked on native fish downloads developed by the NZ Landcare Trust. The Science Learning Hub acknowledges the help of the NZ Landcare Trust in adapting this work.

      Published 18 December 2017, Updated 14 October 2021 Referencing Hub articles
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