Understanding Taonga Freshwater Fish Populations in Aotearoa-New Zealand Prepared for Te Wai Māori Trust September 2017 Prepared by: Erica Williams Shannan Crow Ani Murchie Gail Tipa Eimear Egan Jane Kitson Sue Clearwater Mark Fenwick For any information regarding this report please contact: Erica Williams Programme Leader - Māori and the Freshwater Environment Te Kūwaha - Māori Environmental Research +64-4-386 0366 [email protected] National Institute of Water & Atmospheric Research Ltd Private Bag 14901 Kilbirnie Wellington 6241 Phone +64 4 386 0300 NIWA CLIENT REPORT No: 2017326HN Report date: September 2017 NIWA Project: TOK17301 Quality Assurance Statement Reviewed by: Dr Phillip Jellyman Formatting checked by: Alison Bartley Approved for release by: Dr David Roper Cover photo credits: LEFT – (top to bottom) Grey mullet (Photo: NIWA), Stage II juvenile kōura (Source: Hopkins 1967), Kanakana with lamprey reddening syndrome (Photo: Jane Kitson); MIDDLE – Headwaters of the Rākaia River Photo: Shannan Crow); RIGHT – (top to bottom) Longfin eel (Photo: Stuart Mackay), Freshwater mussel (Photo: Ngaire Phillips), Black Flounder (Photo: Bob McDowall). © All rights reserved. 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Contents Executive Summary ........................................................................................................... 10 1 Introduction ............................................................................................................ 12 1.1 Te Wai Māori Trust ................................................................................................. 12 1.2 Report Scope ........................................................................................................... 12 2 Approach ................................................................................................................. 17 2.1 Distribution Maps ................................................................................................... 17 2.2 Trends in Relative Abundance ................................................................................ 18 2.3 Threat Status ........................................................................................................... 19 3 Tuna (Freshwater Eels) ............................................................................................. 21 3.1 Life Cycle ................................................................................................................. 21 3.2 Distribution ............................................................................................................. 26 3.3 State and Trends in Abundance .............................................................................. 28 3.4 Threat Rankings ...................................................................................................... 33 3.5 Pressures on Populations ........................................................................................ 33 3.6 Management........................................................................................................... 48 3.7 Aquaculture ............................................................................................................ 54 4 Piharau / Kanakana (Lamprey) ................................................................................. 57 4.1 Life Cycle ................................................................................................................. 57 4.2 Distribution ............................................................................................................. 61 4.3 State and Trends in Abundance .............................................................................. 61 4.4 Threat Ranking ........................................................................................................ 61 4.5 Pressures on Populations ........................................................................................ 63 4.6 Management........................................................................................................... 66 5 Kōura / Kēwai (Freshwater crayfish) ......................................................................... 67 5.1 Life Cycle ................................................................................................................. 68 5.2 Distribution ............................................................................................................. 70 5.3 State and Trends in Abundance .............................................................................. 72 5.4 Threat Rankings ...................................................................................................... 73 5.5 Pressures on Populations ........................................................................................ 73 5.6 Management........................................................................................................... 77 Understanding Taonga Freshwater Fish Populations in Aotearoa-New Zealand 3 5.7 Aquaculture ............................................................................................................ 77 6 Whitebait ................................................................................................................ 79 6.1 Life Cycle ................................................................................................................. 83 6.2 Distribution ............................................................................................................. 86 6.3 State and Trends in Abundance .............................................................................. 91 6.4 Threat Rankings ...................................................................................................... 93 6.5 Pressures on Populations ........................................................................................ 94 6.6 Management......................................................................................................... 100 6.7 Aquaculture .......................................................................................................... 103 7 Porohe (Smelt) ....................................................................................................... 105 7.1 Life Cycle ............................................................................................................... 106 7.2 Distribution ........................................................................................................... 106 7.3 State and Trends in Abundance ............................................................................ 108 7.4 Threat Rankings .................................................................................................... 108 7.5 Pressures on Populations ...................................................................................... 108 7.6 Management......................................................................................................... 111 8 Kanae (Mullet) ....................................................................................................... 112 8.1 Life Cycle ............................................................................................................... 113 8.2 Distribution ........................................................................................................... 114 8.3 State and Trends in Abundance ............................................................................ 114 8.4 Threat Rankings .................................................................................................... 116 8.5 Pressures on Populations ...................................................................................... 116 8.6 Management......................................................................................................... 120 9 Pātiki Mohoao (Black flounder) .............................................................................. 121 9.1 Life Cycle ............................................................................................................... 122 9.2 Distribution ........................................................................................................... 122 9.3 State and Trends in Abundance ............................................................................ 122 9.4 Threat Rankings .................................................................................................... 124 9.5 Pressures on Populations ...................................................................................... 124 9.6 Management......................................................................................................... 124 10 Kākahi / Kāeo (Freshwater mussels) ....................................................................... 126 10.1 Life Cycle ..............................................................................................................