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Why is the stream important?

Net-spinning caddisfly
Longfin eel
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The native species living in streams include fish, invertebrates such as caddisflies or snails, and plants including "macrophytes" (large plants), algae and mosses (click here to find out how stream life is collected). In a highly modified setting such as the Hamilton urban area, streams with high bodiversity values are rare, so relatively unimpacted systems such as the streams draining the Mangakotukutuku catchment assume greater significance for local biodiversity. Some species found in the Mangakotukutuku, such as the longfin eel and giant kokopu, are considered nationally threatened by the Department of Conservation. It is surprising what can be living in a stream even when the water appears very dirty!

Aquatic plants and animals not only live in the obvious main parts of the streams, but they also live in less obvious habitats such as small trickles, seepages and springs. These smaller habitats can harbour unusual invertebrate species. In the Mangakotukutuku, they are often relatively unimpacted by human activities and some are  not connected to the stormwater system.

The health of streams is closely linked to activities that go on in the catchment upstream. The types of aquatic 
species present reflect these activities and also local  conditions such as the level of shade and the type of streambed habitat available (e.g., soft sand versus stones and wood). Shade is dependent on the types of plants growing along stream edges. In addition to ensuring activities upstream don't harm streams, it is also important to ensure that local instream conditions are suitable for stream life.

Downstream factors such as barriers to upstream passage for migrating fish also affect the types of aquatic species that occur in the Mangakotukutuku, such as migrating fish.

The Stream Care Group is concerned about upstream, local and downstream threats to Mangakotukutuku Stream.