Estuarine systems in the lower North Island/Te Ika-a-Māui Ranking of significance, current status and future management options Matt Todd, Helen Kettles, Claire Graeme, John Sawyer, Amber McEwan and Lynn Adams Disclaimer: The options for future initiatives outlined in this report should not be viewed as a statement of future strategy or intent by the Department of Conservation or any other statutory organisation. They are intended to promote dialogue within agencies and the wider community. This report is dedicated to the memory of our colleague and friend John Sawyer. John was a passionate and practical advocate for the protection and restoration of rare ecosystems, and for the special fauna and flora of Aotearoa/New Zealand. Cover: An overview of the mouth of the Whakataki River. Photo: Wriggle Coastal Management, © Greater Wellington Regional Council. © Copyright December 2016, New Zealand Department of Conservation ISBN 978-1-98-851410-9 (web PDF) For correspondence regarding this report please contact Department of Conservation lead author H. Kettles at [email protected] Citation: Todd, M.; Kettles, H.; Graeme, C.; Sawyer, J.; McEwan, A.; Adams, L. 2016: Estuarine systems in the lower North Island/Te Ika-a-Māui: ranking of significance, current status and future management options. Department of Conservation, Wellington, New Zealand. 400 p. In the interest of forest conservation, we support paperless electronic publishing. Acknowledgements Due to the diversity of information contained in this report, the process for developing it was very much a collaborative effort. It involved many people with broad or specific knowledge about many different disciplines, including ecology, botany, zoology, places and history. We wish to acknowledge the large number of people who assisted in bringing this information together in one place as a resource for us all. It has been a big job to compile it, and the enthusiasm for the project and sharing of knowledge has been much appreciated. We thank field staff in DOC local offices for providing logistical and field support when the estuarine systems were being surveyed, in addition to inputting their local knowledge. In particular, we thank Colin Giddy, Richard Gill, Daniel Kawana, Jessica Kereama, David Moss, Chau-Phing Ong, Nikki Pindur, Clinton Purches, Tony Silbery, Peter Simpson, Eric Stone and Tene Tangatatai. Many other DOC staff also added value with their knowledge and provided critical comments on earlier drafts of this report that led to substantial improvements. This includes a range of technical specialists largely from the former Conservation Support Unit of the Wellington Hawke’s Bay Conservancy, particularly Jeremy Rolfe (overview, plants), Emily Greenberg (planning), Richard Nester (historic), David Bishop (land status), Emma Greig and Claudia Hill (recreation), Lindsay Millard and Paul Hughes (GIS), Kendra Travaille and Tom Allan (mapping data), Rebecca Hayter and Juliet O’Connor (map production), Hugh Robertson (birds), and Philippe Gerbeaux (classifications). Matthew Bauer and Amanda Todd provided editorial and proof reading skills with support from Anna Saunders, and Lynette Clelland produced the final document. We owe much gratitude to staff from GWRC who contributed a large amount of time to engage, debate and add value to this report, including Megan Oliver, Lucy Harper, Harvey Philips, Tim Park, Juliet Milne, Robyn Smith, Alton Perrie, Sharyn Westlake, Mike Urlich, Melanie McElwee, Alistair Allan, Philippa Crisp, Gareth Cooper, Richard Romijn, Kim Broad, Rob Masters, Toni de Lautour, Jo Fagan, Rebecca Bird, Justin McCarthy, Amanda Cox, Fiona Colquhoun and Ali Caddy. Staff from other councils also provided valued time contributing their knowledge to the report: Logan Brown and Aaron Madden (Horizons Regional Council), Rob Cross (Kāpiti Coast District Council), Myfanwy Emeny and Amber Bill (Wellington City Council), and Keith Calder and Chris Freeman (Porirua City Council). Matiu Park from Boffa Miskell Limited has assisted with information on Ōkowai Lagoon and Richard Ford from the former Ministry of Fisheries (now the Ministry for Primary Industries) provided comments on an earlier draft. Terry Hume (National Institute of Water and Atmospheric Research; NIWA) gave us permission to use his estuarine classification diagrams, and Keith Michael and Malcolm Francis (also from NIWA) provided expert input on aspects of the report. We appreciate the large number of people who gave their time to help with this report. Their expertise and local perspective added much value. Thank you Leigh Stevens (Wriggle Coastal Management), Feriel Falconer (Friends of the Waikanae River Inc.), Frances Lee (Trelissick Park Group), John Wells (Guardians of Pāuatahanui Inlet), Ian Armitage (OSNZ), Penny Gaylor and Max Lutz (Friends of the Ōtaki River), Wellington Hawke’s Bay Conservation Board, Dave Hansford (Makaracarpas), Billie Taylor (Te Horo Residents Association), Jim Mikoz (Wellington Recreational Marine Fishers’ Association), John McLachlan (Kāpiti-Mana Forest & Bird), Russell Bell (Lower Hutt Forest & Bird), Sue McIntosh (Waitohu Stream Care Group), Trevor Thompson (QEII Wairarapa) and the Wellington and Wairarapa branches of OSNZ. We are grateful to numerous landowners for land access, and thank Anders Crofoot (Castle Point Station, Wairarapa Fed. Farmers), George Tatham (Matāriki Station) and Chris Tatham (Homewood Station) for their time and input. We also thank Tanya Piejus and Don Ravine for the use of their photographs. Estuarine systems in the lower North Island 3 4 Estuarine systems in the lower North Island CONTENTS Executive summary 3 Introduction 4 1. Manawatū River 21 2. Wairarawa Stream 33 3. Hōkio Stream 38 4. Waiwiri Stream 46 5. Ōhau River 51 6. Waikawa Stream 59 7. Waitohu Stream 67 8. Ōtaki River 75 9. Mangaone Stream 83 10. Kukutauaki Stream 89 11. Waimeha Stream 94 12. Waikanae River 101 13. Wharemauku Stream 113 14. Whareroa Stream 118 15. Wainui Stream 125 16. Taupō Stream 131 17. Te Awarua-o-Porirua Harbour 137 18. Mākara Stream 167 19. Kaiwharawhara Stream 175 20. Korokoro Stream 182 21. Te Awa Kairangi/Hutt River 187 22. Waiwhetū Stream 198 23. Parangarahu Lakes 205 24. Wainuiōmata River 215 25. Lake Ōnoke and lagoons 221 26. Whāngaimoana Stream 244 27. Cape Palliser streams (Mākotukutuku, Pararaki and Ōtakaha) 250 28. Ōpouawe River 255 29. Āwheaiti Stream 260 30. Āwhea River 264 31. Ōterei River 270 32. Rerewhakaaitu River 276 33. Pāhāoa River 281 34. Kaiwhata River 286 35. Waikaraka Stream 292 36. Patanui Stream 296 37. Waioronu Stream 301 38. Motuwaireka Stream 306 39. Whareama River 312 40. Otahome Stream 319 41. ‘Humpy’ Stream 324 42. Ngākauau Stream 328 43. Whakataki River 333 44. Ōkau Stream 339 45. Mātaikona River 345 46. Ōwāhanga River 351 47. Ākitio River 356 48. Waimata River 362 Appendix 1 Hume et al. (2007) classification of New Zealand’s estuarine systems—the five classes of estuarine systems represented in this region 366 Appendix 2 Sites that were excluded from the report 368 Appendix 3 Scoring system used to rank the relative importance of estuarine sites 369 Appendix 4 Criteria scores for individual estuarine systems in the Lower North Island (Te Ika-a-Māui) 370 Appendix 5 List of the 34 estuarine sites assessed for risks by Greater Wellington Regional Council 372 Appendix 6 Criteria for listed threat classifications (adapted from Townsend et al. 2008) 373 Appendix 7a Native plants mentioned in the text and their threat status 374 Appendix 7b Exotic plants mentioned in the text 376 Appendix 8 Native animals mentioned in the text and their threat status 378 Appendix 9 Site land status and existing rankings explanations 383 Appendix 10 Habitat classification as per Atkinson (1985) 386 Appendix 11 Reference list for the entire report 388 Estuarine systems in the lower North Island/ Te Ika-a-Māui Ranking of significance, current status and future management options Matt Todd2, Helen Kettles1, Claire Graeme1, John Sawyer1, Amber McEwan3 and Lynn Adams1 1 Department of Conservation, PO Box 10-420 The Terrace, Wellington 6143, New Zealand Email: [email protected] 2 Current address: 8 Walden Street, Wellington 6022, New Zealand 3 Riverscapes Freshwater Ecology Limited: 13 Weka Place, Masterton 5810, New Zealand Estuarine systems in the lower North Island 1 2 Estuarine systems in the lower North Island Executive summary Estuarine ecosystems, where saltwater meets freshwater, are uncommon ecosystems that are of high value and under increasing pressure from a range of threats. With the growing awareness of their importance and the need to conserve them, this document has been produced as a resource for all those with an interest in estuarine ecosystems, including conservation managers, landowners, tangata whenua, community groups, resource managers, scientists and recreational users. A large number of organisations and individuals from these interest groups have contributed valuable knowledge to this document, making it a highly practical resource. It also complements online resources that have been developed to assist community restoration aspirations for estuarine systems around New Zealand. This document is the first attempt to bring together a large amount of information on the estuarine ecosystems that occur in the lower North Island (Te Ika-a-Māui) of New Zealand. We assess the current state and future potential of 48 sites from the Manawatū river mouth on the west coast to the Waimata river mouth on the eastern Wairarapa coast. We