State of the Environment Report The Health of Freshwater Fish Communities in Tasman District 2011 State of the Environment Report The Health of Freshwater Fish Communities in Tasman District September 2011 This report presents results of an investigation of the abundance and diversity into freshwater fish and large invertebrates in Tasman District conducted from October 2006-March 2010. Streams sampled were from Golden Bay to Tasman Bay, mostly within 20km of the coast, generally small (1st-3rd order), with varying types and degrees of habitat modification. The upper Buller catchment waterways were investigated in the summer 2010. Comparison of diversity and abundance of fish with respect to control-impact pairs of sites on some of the same water bodies is provided. Prepared by: Trevor James Tasman District Council Tom Kroos Fish and Wildlife Services Report reviewed by Kati Doehring and Roger Young, Cawthron Institute, and Rhys Barrier, Fish and Game Maps provided by Kati Doehring Report approved for release by: Rob Smith, Tasman District Council Survey design comment, fieldwork assistance and equipment provided by: Trevor James, Tasman District Council; Tom Kroos, Fish and Wildlife Services; Martin Rutledge, Department of Conservation; Lawson Davey, Rhys Barrier, and Neil Deans: Fish and Game New Zealand Fieldwork assistance provided by: Staff Tasman District Council, Staff of Department of Conservation (Motueka and Golden Bay Area Offices), interested landowners and others. Cover Photo: Angus MacIntosch, University of Canterbury ISBN 978-1-877445-11-8 (paperback) ISBN 978-1-877445-12-5 (web) Tasman District Council Report #: 11001 File ref: G:\Environmental\Trevor James\Fish, Stream Habitat & Fish Passage\ FishSurveys\ Reports\ FreshwaterFishTasmanDraft2011. Doc Trevor James Tom Kroos Resource Scientist Managing Director Tasman District Council Fish & Wildlife Services 189 Queen St PO Box 3207 Private Bag 4 Richmond RICHMOND Nelson 7050 [email protected] [email protected] Executive Summary Tasman District Council (TDC) has functions under the Resource Management Act to monitor and manage the life-supporting capacity and natural character of wetlands, lakes and rivers and their margins, as well as significant habitats for indigenous fauna and introduced sports fish such as trout and salmon. The overall aim of Council’s Freshwater Fish monitoring programme is to compare the diversity and abundance of freshwater fish in streams of varying habitat condition caused by certain land use and stream disturbance activities. This information can also be used to identify streams of particularly high value that require greater protection with respect to certain habitat disturbances which is used in drafting the Tasman Resource Management Plan Part IV and with the processing of specific resource consent applications. More specific objectives include: • compare the diversity and abundance of freshwater fish in streams of varying habitat condition caused by various resource use activities, particularly works in the beds and banks of streams. • assess the efficacy of stream rehabilitation projects, such as riparian plantings, and restoration at structures that present a barrier to fish migration • provide baseline data from which to build a more complete picture of fish distribution and abundance patterns in the region. This information can also be used to identify streams of particularly high value that require greater protection with respect to certain habitat disturbances which will then be used in the Tasman Resource Management Plan Part IV and with the processing of specific resource consent applications. This project involved cooperation between TDC, Department of Conservation (DoC), and Fish and Game New Zealand Nelson Marlborough Region (F&G) for survey design and implementing fieldwork. All three organisations have responsibility for monitoring fish populations under a range of legislation and have over-lapping objectives in this programme. Contract assistance was provided by Fish & Wildlife Services. The streams sampled were generally small (1st-3rd order) with varying types and degrees of habitat modification. From 2006-2010 a total of 247 sites were assessed on 89 individual streams, with a focus on coastal streams in Golden and Tasman Bays as well as some streams in the upper Buller and Motueka catchments. Streams selected were primarily sampled by backpack electric fishing or spotlighting but, in some circumstances, gee minnow traps and/or fyke nets were employed. In Tasman there are 20 species of indigenous freshwater fish, fifteen of which are diadromous (migrate to and from the sea to complete their life cycle). In addition there are three sport-fish, the most abundant of which is brown trout. Freshwater fish were recorded in all but three sites with an average number of 3.0 fish species/site and a maximum of 8 fish species/site. When combining spring and summer surveys, longfin eels/tuna were observed most frequently (74.5% of sites), followed by adult inanga (46%) and shortfin eel/tuna (45%). Longfin eel, a species recognized as ‘in decline’ nationally, is the most widespread of any freshwater fish species in the district. The relatively high abundance of eels and inanga was a feature of the stream habitats targeted. Inanga migrating into freshwater during spring investigations (n=87) were abundant (>20 individuals/site) in 28% of all sites sampled. Inanga, common bully and shortfin eel have a tolerance to poor water quality and degraded habitat, particularly smaller farmland streams with silt-laden beds, moderate sediment load, intermediate in- stream cattle disturbance and streamside corridors dominated by pasture grasses. However, even these less habitat-sensitive fish have been found in much fewer numbers in streams or drainage ditches that are dug out regularly and, for inanga and common bully, streams with excessive aquatic plant growth over the last few decades. Banded kokopu, koaro, shortjaw kokopu, giant kokopu, torrentfish, bluegill bully and redfin bully have been found to be more sensitive to disturbance and they are absent or rare in sites where streamside vegetation has been removed, channels straightened or where there are high loads of fine sediment input by, for example, machinery or larger farm animals. Habitat-sensitive native fish species were observed in 21% of the sites surveyed. Giant kokopu, for example, are very rare in the region (only 44 records at 42 sites since 1990; NZFFDB) due to their preference for deeper, slow-flowing streams associated with lowland wetlands which are now also very rare within the region. This relationship between quality and quantity of habitat and the health of fish communities is similar to that found elsewhere in New Zealand. Brown trout, followed by eels, are the most significant freshwater fishery in the region. In the Motueka River, one of New Zealand’s best trout fisheries, numbers have rebounded since the mid 1990’s but fluctuate from year to year depending on flooding, food supplies and water temperatures. Based on distribution patterns and abundance of native fish compared to trout, it would appear that trout and eels dominate larger waterways (over approximately 3 cumecs) and native fish appear to dominate smaller waterways that discharge directly to the coast. In fact there are no trout or very few in many of these streams so native fish will not be affected by trout predation. Trend analyses for freshwater fish populations over time is not possible due to inadequate data available, pointing out the importance of future data collection. A search of the NIWA Freshwater Fish Database provided 59 historical records that can be compared to sites sampled in this monitoring programme. Caution should be considered when comparing historical records to 2006-2010 results as survey methods and seasons sampled may be dissimilar. Access to suitable habitat and spawning grounds for migratory fish is largely prevented due to migration barriers such as undercut culverts, weirs, dams, and tidal flap gates. Water takes are also known to dry up a significant area of streams in summer. Several survey results demonstrated the success of fish passage restoration projects such as that on Tui Stream (Wainui Bay), Reservoir Creek (Richmond) and Maisey Creek (Waimea estuary). The general absence of habitat-sensitive native species from modified streams provide justification for implementing measures that better manage habitats of native fish from activities such as drain clearance, stream straightening, cattle trampling, fine sediment discharges, riparian vegetation removal and other land uses impacting the beds and riparian zones of small order streams in the Tasman District. Avoiding, mitigating or remediating adverse effects on small lowland or spring-fed streams located within 10-15km of the coast are particularly important as these streams have both, the highest fish species abundance and diversity and the most vulnerable fish species. Acknowledgements Tasman District Council would like to thank all the people who have assisted in this monitoring programme. In particular we would like to thank landowners who provide access to monitoring sites and NIWA for data from the New Zealand Freshwater Fish Database (NZFFD). Thanks also to Cawthron Institute and Landcare Research which assisted with field investigations in the Motueka River Catchment under the Integrated Catchment Management (ICM) project in 2006. Thanks to Network Tasman and their support for fisheries