Assessment of Significant Salmon Spawning Sites in the Canterbury Region
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Assessment of significant salmon spawning sites in the Canterbury region NIWA Client Report: CHC2006-097 July 2006 NIWA Project: ENC06515 Assessment of significant salmon spawning sites in the Canterbury region M. J. Unwin Prepared for Environment Canterbury NIWA Client Report: CHC2006-097 July 2006 NIWA Project: ENC06515 National Institute of Water & Atmospheric Research Ltd 10 Kyle Street, Riccarton, Christchurch P O Box 8602, Christchurch, New Zealand Phone +64-3-348 8987, Fax +64-3-348 5548 www.niwa.co.New Zealand © All rights reserved. This publication may not be reproduced or copied in any form without the permission of the client. Such permission is to be given only in accordance with the terms of the client's contract with NIWA. This copyright extends to all forms of copying and any storage of material in any kind of information retrieval system. Contents Summary i 1. Introduction 1 2. Overview of the Canterbury salmon fishery 3 3. Sources of information 7 3.1. Spawning populations 7 3.1.1. The LEDB 7 3.1.2. FGNZ records 9 3.2. Angler surveys 10 3.2.1. The 1978/79 National Angling Survey 10 3.2.2. The 1994/96 and 2001/02 National Angling Surveys 10 3.2.3. Hatchery returns and straying 10 4. Criteria for ranking salmon spawning habitats 11 4.1. Habitat value 11 4.2. Fishery value 12 4.3. Other values 14 4.4. Overall value 15 5. Schedule of significant salmon spawning sites 17 5.1. Nationally significant sites 17 5.2. Regionally significant sites 19 5.2.1. Waiau River 19 5.2.2. Hurunui River 19 5.2.3. Waimakariri River 20 5.2.4. Rakaia River 22 5.2.5. Ashburton River 22 5.2.6. Rangitata River 24 5.2.7. Orari River 24 5.2.8. Opihi River 25 5.2.9. Waitaki River 25 6. Discussion 27 7. Acknowledgements 28 8. References 29 Appendix 1: Significant salmon spawning sites as listed in schedule WQN14 Appendix 2: Sites being used by spawning salmon Appendix 3. Nationally and regionally important salmon spawning sites. Reviewed by: Approved for release by: Gavin James Don Jellyman Summary Environment Canterbury (ECan) has recently notified a variation to the Proposed Natural Resources Regional Plan (PNRRP) for managing the region’s water resources. As input to this process ECan had previously commissioned an inventory of salmonid habitats in the Canterbury region, which was published in 2000 as a technical report and GIS database. ECan subsequently used this database to compile a list of significant salmon spawning habitats (Schedule WQN 14). However, this list contained a number of anomalies, leading to a 2006 request from ECan to NIWA for a critical review of Schedule WQN 14 and the underlying GIS database. The main outputs required of this review were: • development of criteria for ranking salmon spawning habitats in terms of their local, regional, and/or national importance for sustaining the salmon fishery; and • application of these criteria to review the list of the salmon spawning habitats in Schedule WQN 14, and prepare a list of significant salmon spawning sites. The ECan database identifies 183 sites as valuable for salmon spawning, in 16 catchments, from the Clarence River to the Waitaki River. Most (170) of these are used by sea run Chinook salmon, and the remainder by lake limited Chinook salmon or sockeye salmon. Fish & Game New Zealand records, and published reports on angler surveys (dating back to c. 1980) were used to gauge run strength and angling value for each individual site, supplemented (as appropriate) by data on recaptures of tagged salmon of hatchery origin during the 1980s and 1990s held in NIWA’s research databases. Individual spawning sites were ranked as high, medium, or low value, taking into account the relative usage of each site within each catchment, and the temporal fidelity with which it is used over a period of years. Sites were ranked as High value if spawning fish were consistently present in all years, and generally accounted for at least 10% of total spawning. Sites were ranked as Medium value if spawning fish were present in most seasons, and sometimes accounted for over 10% of total spawning. Sites were ranked as Low value if spawning populations were ephemeral or highly variable, and could be absent for several consecutive years. Angling value was assessed as either nationally, regionally, or locally significant, based on criteria which were developed from the 1978/79 National Angling Survey, and which have since been widely adopted by resource managers. Fisheries are considered Nationally significant if annual spawning runs can exceed ten thousand fish, and annual angling effort usually exceeds ten thousand angler-days and is distributed throughout the length of the river. Fisheries are considered Regionally significant if annual spawning runs generally number a few thousand fish, and angling effort is usually between two and ten thousand angler-days per year. Fisheries are considered Locally significant if annual spawning runs rarely exceed a few hundred fish, and salmon angling is largely an episodic activity which Assessment of significant salmon spawning sites in the Canterbury region i confined to the river mouth. Other attributes which were taken into account as appropriate were enhancement value (i.e., streams associated with hatcheries); restoration potential (i.e., degraded streams which could contribute significantly to the fishery if appropriate restoration measures were implemented); diversity of angling opportunity; and scientific interest. These habitat and fishery criteria are used to define a two way matrix in which individual sites can be classified and grouped with others of similar value. The basis for this classification scheme is that 1. sites in catchments which support nationally significant fisheries will generally be more important than those associated with regionally significant fisheries, which in turn are more important than locally significant fisheries; and 2. within each catchment, site value is directly related to habitat value. Thus, individual site value falls on a spectrum from high value habitats in nationally significant fisheries to low value habitats in locally significant fisheries. This spectrum comprises five levels: • Nationally significant: high value sites in nationally significant fisheries. Essential for maintaining the salmon fishing resource; • Regionally significant: high value sites in regionally significant fisheries, and medium value sites in nationally significant fisheries. Important for maintaining the salmon fishing resource; • Locally significant: high value sites in locally significant fisheries, medium value sites in regionally significant fisheries, and low value sites in nationally significant fisheries. Significant for maintaining the local angling resource, and may be regionally significant on a case by case basis; • Little significance: medium value sites in locally significant fisheries, and low value sites in regionally significant fisheries. At best locally significant; • No significance: low value sites in locally significant fisheries. Incidental to overall maintenance of fishery. Based on these criteria, forty-eight sites were identified as of at least local significance, including 18 of national significance and 14 of regional significance. These are associated with Chinook salmon fisheries in nine catchments, and represent four nationally important fisheries (Waimakariri River, Rakaia River, Rangitata River, Waitaki River); three regionally important fisheries (Hurunui River, Opihi River, and Lake Coleridge); and four locally important fisheries (Waiau River, Ashburton River, Orari River, Lake Heron). Also included are four spawning sites important for sockeye salmon in the Assessment of significant salmon spawning sites in the Canterbury region ii upper Waitaki catchment. Details of all sites are tabulated in a series of Appendices, and are also shown in map form based on an updated GIS layer provided by ECan. The revised Schedule of salmon spawning sites developed in this review has attempted to resolve all of the major inconsistencies in the existing Schedule WQN 14. Seven of the sixteen catchments listed in Schedule WQN 14 have been dropped, and all upstream and downstream map references have been reviewed. Other changes reflect the addition of sites in the Waimakariri catchment (which were excluded from the original Schedule), inclusion of sites used by landlocked sockeye salmon, and changes to the GIS layers for several upper Rakaia River sites to correct long-standing errors in their representation in Topomap Series NZMS260. However, all rankings remain partly subjective, and the spatial extent of each site should be verified by ground truthing before taking any management action. This review has focussed on the recent (10-20 year) historical record, consistent with ECan’s requirements and the timeframe adopted when compiling Schedule WQN 14. In doing so, it risks overlooking historically important fisheries which are now degraded to the point where they are no longer viable. Such fisheries include the Ashburton, Opihi, and Hataramea, as well as smaller rivers such as the Maerewhenua and Waihao. While some such waters may now have very limited potential, others may still be amenable to more interventionist or protective management strategies to restore some or all of their former value. For these reasons, the present report should be interpreted as an assessment of the current status quo, rather than defining the scope of the Canterbury salmon fishery for all time. Should ECan wish to pursue future enhancement or restoration options, further consultation with end users (particularly FGNZ) would be appropriate to better identify candidate rivers and spawning waters. Assessment of significant salmon spawning sites in the Canterbury region iii 1. Introduction Environment Canterbury (ECan) has recently notified a variation to the Proposed Natural Resources Regional Plan (PNRRP) which establishes objectives, policies and methods for managing the region’s water resources. As input to this process ECan commissioned a desktop study to compile an inventory of salmonid habitats, based on published and unpublished sources.