Lakes Ngāpouri, Ngāhewa and Tutaeinanga - Monitoring of kōura and common bully using the tau kōura
Report: TR 2017/07
Author: Ian Kusabs & Associates Ltd
About this report
Lakes Ngāpouri, Ngāhewa and Tutaeinanga are located in the geothermal area around Maungakakaramea and Waiotapu. These lakes are rich in nutrients and frequently experience nuisance cyanobacteria blooms driven by high nitrogen and phosphorus inputs from the catchment and a high internal P load released from the sediments during summer. Kōura are an important component of lake food webs and support important customary fisheries in the Te Arawa lakes.
The aim of this study was to provide baseline information on the kōura populations in the Waiotapu lakes to underpin a restoration plan for the three lakes.
No kōura were found in this survey of lakes Ngāpouri, Ngāhewa and Tutaeinanga. It is probable that multiple stressors associated with the nutrient enrichment process, particularly rapid and prolonged lack of dissolved oxygen, have led to kōura disappearance in the Waiotapu lakes. Major improvements in lake water quality are required before kōura populations can be re-established in the lakes. The successful re-establishment of kōura should be a key long-term goal of the Waiotapu lakes restoration programme. It is envisaged that kōura in the inflowing tributaries will provide a source of recruitment for the lakes when water quality conditions improve.
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| Contents | ||
| 1 | Introduction | 1 |
| 2 | Methods | 2 |
| 2.1 | Tau kōura location and lay out | 2 |
| 2.2 | Fish measurement | 2 |
| 3 | Results | 4 |
| 3.1 | Sampling conditions | 4 |
| 3.2 | Kōura and fish species present | 4 |
| 3.3 | Common bully | 4 |
| 4 | Discussion | 7 |
| 4.1 | Kōura | 7 |
| 4.2 | Fish | 8 |
| 4.3 | Lake restoration | 9 |
| 5 | Summary and recommendations | 10 |
| 6 | Acknowledgements | 11 |
| 7 | References | 12 |