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The streams and other aquatic habitats

Freshwater life

Fish

Ten species of native fish are known  in the Mangakotukutuku Stream system. All of these species have been caught in Sandford Park.

Native fish in the stream Giant kokopu and longfin eel are considered threatened species by the Department of Conservation. In addition to these species,  there are historical reports of mudfish in a small side stream of the Te Anau branch.

Two species of introduced fish have also been reported from the catchment. Koi carp was found in the Mangakotukutuku below Peacockes Rd and has been sighted once upstream of the culvert when water levels in the Waikato River were high. Gambusia has been found in the lower part of the right branch and the Peacockes tributary. Pest fish do not appear to be widespread in the stream network. Let's keep it that way!

Giant kokopu Longfin eel

Stream invertebrates

Invertebrates are animals without backbones, such as mayflies, caddisflies, worms and snails, that live for all or part of their lives in freshwater. They often live under stones or on  wood and plants under the water, and some have adult flying stages that live on vegetation near the stream.

Wilding (1998) reported on invertebrates at two sites on the Mangakotukutuku in December 1996 and January 1997. Sampling at these sites was continued annually by Environment Waikato until 2004 at Pelorus St and is being done on a ongoing annual basis on the mainstem above Peacockes Rd.


The 1996/97 sampling recorded 10-11 types of invertebrate at the Peacockes and Pelorus sites, including three species of caddisfly. Samples were dominated by snails, worms and crustaceans.
Adult caddisflies
Caddisfly larvae living in the stream pupate over summer and turn into flying adults that live on the land. These adults are attracted to ultra-violet light and this is often used as a method to catch them. Light-trapping at 7 sites in December 2005 by the Mangakotukutuku Stream Care Group caught 23 species of adult caddisflies, with between 4 and 10 species per site, including several species that are not commonly encountered. Thanks to Brian Smith of NIWA for identifying the caddisflies for us.

The larvae of many of these caddisfly species probably live in small tributaries and seepages that flow into the main branches of the Mangakotukutuku and are not highly influenced by stormwater inputs.

Crayfish are abundant in parts of the Peacockes branch above the urban area, and have been found in small numbers in other parts of the catchment. Crayfish are usually rare in Hamilton's other urban streams.

Information on the types of invertebrates living in a stream can be summarised into single numbers called "metrics" that reflect the tolerance of invertebrate community to stress from pollution, high sediment levels etc. One of the most commonly used metrics is called the Macroinvertebrate Community Index or MCI. When MCI scores drop below 80, streams are generally considered to have  poor water or habitat quality
Adult caddisfly
MCI scores over 1997 to 2004 have averaged 81 and 71 for the Peacockes and Pelorus sites, respectively  (data provided by Environment Waikato). We think MCI scores can go higher if stream habitat is improved.

Stream plants

Most parts of Mangakotukutuku Stream are too turbid to support aquatic plants. However, some growths of the shade-tolerant native charophyte Nitella and the floating-leaved starwort (Callichtriche stagnalis) do occur in shallow margins. Filamentous algae and mosses are also present in some parts on stable substrates such as large rocks and logs.

Aquatic habitats

There are around 18 km of stream mapped in the Mangakotukutuku catchment. In addition to the three main branches which have rural headwaters, there are several small tributary streams that start in the suburbs and have varying levels of influence from stormwater drainage. Small seepages also occur throughout the gullies. These small streams and seepages can provide important habitat  for native species. 

Poor streambed stability has been identified as the major ecological stressor in the Mangakotukutuku, followed by lack of habitat cover and heavy metal contamination (Williamson 2001). Peak flows from stormwater along with rural runoff contribute to streambed instability and poor habitat quality. The main part of Mangakotukutuku Stream running through Sandford Park has particularly severe bank erosion and fine sediment build-up on the streambed.
 
Sediment build-up in mainstem

Water quality

Along with habitat quality, water quaity is a very important factor influencing the range of species that can live in the stream. The Mangakotukutuku has been monitored for water quality at Peacockes Road by Environment Waikato monthly since 1990 (Tulagi 2012). Two other major streams in Hamilton City, the Kirikiriroa and Waitawhiriwhiri, are also monitored for water quality.

See monitoring data on the Land and Water Aotearoa (LAWA) website

What is measured? How much is there?
(
based on annual
median values in 2005)
Is that good or bad? Is it going up or down? How does it compare to the two other major Hamilton streams?
Turbidity  25 NTU Poor Stable Lowest
Water temperature 14.7oC OK Stable Similar
Dissolved oxygen 90%  OK Stable Highest
Water acidity (pH) 7.0 OK Going down Similar
Ammonia 0.72 g N/m3 OK Stable Lowest
Phosphorus 0.43 g/m3 Poor Going up Highest
Bacteria (E. coli) 1260 per 100 mL Poor Stable Highest

Turbidity - a measure of light scattering or light availability for plant growth; tells us something about how dirty the water is

Water temperature - measured using a thermometer; tells us how hot the water gets

Dissolved oxygen - amount of oxygen dissolved in the water as a percentage of oxygen saturated water; tells us whether there is enough oxygen for aquatic life

Water acidity - measure of whether the water is acid (pH below 7) or alkaine (pH above 7); water that is too acid or too alkaline can be bad for aquatic life

Ammonia - measure of ammoniacal nitrogen which can be toxic to fish in high concentrations

Bacteria (E. coli) - number of colony forming Escherichia coli bacteria in 100 mL of streamwater; tells us how polluted the water is from mammalian waste

Find out more about water quality and sources of contaminants in Mangakotukutuku Stream.

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