Ecosystem health in Wellington City urban streams: Stage one summary report
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There is an extensive network of streams in the Wellington City area. Many of these
streams have been piped and historically there has been minimal information on their ecological health (in terms of habitat condition, macroinvertebrate community health and fish populations). To address this knowledge gap, Greater Wellington Regional Council (GWRC) has worked with Wellington City Council (WCC) over the last three years to better understand the ecological health of Wellingtons piped and open urban streams.
Monitoring commenced in 2016 and has continued over the summer months until 2019. During this time, a range of open urban streams in Wellington City have been surveyed on a single occasion to assess habitat condition, macroinvertebrate community health
and fish populations. During this period habitat condition, macroinvertebrate and fish populations were also surveyed in piped streams by EOS Ecology.
The purpose of the monitoring is to provide a baseline of information from which a long-term monitoring programme for Wellington City stream ecosystem health can be developed. This monitoring programme is needed to report against National Policy Statement for Freshwater Management and GWRC Proposed Natural Resources Plan objectives for ecosystem health. Information is also needed to inform a range of Wellington City Council and Wellington Water strategies aimed at reducing the impact of urban land use on Wellington City stream ecosystems. This report presents the results of baseline monitoring for open streams. Results for the piped stream survey are attached in separate reports. Ecosystem health data collected to date indicate Wellington City urban streams contain a range of values related to habitat, macroinvertebrates and fish. Key findings were:
Macroinvertebrate communities were generally in better condition in streams with less urban landuse and impervious area in the upstream catchment.
Fish communities within urban streams were generally in fair to poor condition. However, there is greater fish diversity in sections of stream with direct connection
to the sea.
Inanga spawning was occurring in bank vegetation in the lower Kaiwharawhara Stream.
Banded kokopu and eel species were the most abundant fish species present across the majority of sites surveyed. Native fish species present included at risk and declining species such as koaro, inanga, redfin bully, longfin eel and giant kokopu.
Barriers to fish movement are likely to be one of the major pressures influencing fish communities in Wellington urban streams. The only fish species found
upstream of piped sections of stream are climbing species (banded kokopu, koaro
and eel species). The presence of banded kokopu and eels in piped stream sections
was confirmed in the piped stream survey.
Macroinvertebrate and fish communities in Wellington City streams appear to be driven by different environmental stressors. The healthiest macroinvertebrate communities were generally found higher in catchments where habitat and water quality degradation from urban runoff is less. In contrast, fish communities were generally in better condition at sites lower in the catchment where there were likely to be less barriers to migration to and from the sea. This finding highlights the need
for a whole of catchment approach for improving ecosystem health of Wellington
City streams.
The initial piped stream survey has shown that some sections of piped streams have habitat which supports fish and macroinvertebrate life, however species richness and abundance is greater in free flowing streams. The complete enclosing of open channels significantly reduces habitat quality for stream life and means only a
subset of available taxa within catchments are able to persist there.
The next stage will involve design of a long term monitoring programme of Wellington
City stream ecosystem health. This will involve working with WCC to identify
objectives of the programme, monitoring sites, parameters to be measured, sampling frequency and reporting required. Targeted investigations needed to answer specific questions around management actions will also be identified. The programme will be designed in 2019/20 for implementation in 2020/21.
Keywords: Urban, fish, habitat, macroinvertebrate, ecosystem health
streams have been piped and historically there has been minimal information on their ecological health (in terms of habitat condition, macroinvertebrate community health and fish populations). To address this knowledge gap, Greater Wellington Regional Council (GWRC) has worked with Wellington City Council (WCC) over the last three years to better understand the ecological health of Wellingtons piped and open urban streams.
Monitoring commenced in 2016 and has continued over the summer months until 2019. During this time, a range of open urban streams in Wellington City have been surveyed on a single occasion to assess habitat condition, macroinvertebrate community health
and fish populations. During this period habitat condition, macroinvertebrate and fish populations were also surveyed in piped streams by EOS Ecology.
The purpose of the monitoring is to provide a baseline of information from which a long-term monitoring programme for Wellington City stream ecosystem health can be developed. This monitoring programme is needed to report against National Policy Statement for Freshwater Management and GWRC Proposed Natural Resources Plan objectives for ecosystem health. Information is also needed to inform a range of Wellington City Council and Wellington Water strategies aimed at reducing the impact of urban land use on Wellington City stream ecosystems. This report presents the results of baseline monitoring for open streams. Results for the piped stream survey are attached in separate reports. Ecosystem health data collected to date indicate Wellington City urban streams contain a range of values related to habitat, macroinvertebrates and fish. Key findings were:
Macroinvertebrate communities were generally in better condition in streams with less urban landuse and impervious area in the upstream catchment.
Fish communities within urban streams were generally in fair to poor condition. However, there is greater fish diversity in sections of stream with direct connection
to the sea.
Inanga spawning was occurring in bank vegetation in the lower Kaiwharawhara Stream.
Banded kokopu and eel species were the most abundant fish species present across the majority of sites surveyed. Native fish species present included at risk and declining species such as koaro, inanga, redfin bully, longfin eel and giant kokopu.
Barriers to fish movement are likely to be one of the major pressures influencing fish communities in Wellington urban streams. The only fish species found
upstream of piped sections of stream are climbing species (banded kokopu, koaro
and eel species). The presence of banded kokopu and eels in piped stream sections
was confirmed in the piped stream survey.
Macroinvertebrate and fish communities in Wellington City streams appear to be driven by different environmental stressors. The healthiest macroinvertebrate communities were generally found higher in catchments where habitat and water quality degradation from urban runoff is less. In contrast, fish communities were generally in better condition at sites lower in the catchment where there were likely to be less barriers to migration to and from the sea. This finding highlights the need
for a whole of catchment approach for improving ecosystem health of Wellington
City streams.
The initial piped stream survey has shown that some sections of piped streams have habitat which supports fish and macroinvertebrate life, however species richness and abundance is greater in free flowing streams. The complete enclosing of open channels significantly reduces habitat quality for stream life and means only a
subset of available taxa within catchments are able to persist there.
The next stage will involve design of a long term monitoring programme of Wellington
City stream ecosystem health. This will involve working with WCC to identify
objectives of the programme, monitoring sites, parameters to be measured, sampling frequency and reporting required. Targeted investigations needed to answer specific questions around management actions will also be identified. The programme will be designed in 2019/20 for implementation in 2020/21.
Keywords: Urban, fish, habitat, macroinvertebrate, ecosystem health