Fisheries Technical Manual 7 Trout Fisheries Management Advice Management advice for trout, grayling and Arctic char fisheries Fisheries Technical Manual No. 7 N. Giles, J. Westgarth* and N Hewlett* * Environment Agency Research Contractor: Dr Nick Giles & Associates 50 Lake Road, Verwood, Dorset, BH31 6BX R&D Technical Report W2-045/TR i Version 1.0-02/04 Fisheries Technical Manual 7 Trout Fisheries Management Advice Publishing Organisation Environment Agency, Rio House, Waterside Drive, Aztec West, Almondsbury, BRISTOL, BS32 4UD. Tel: 01454 624400 Fax: 01454 624409 Website: www.environment-agency.gov.uk © Environment Agency 2004 February 2004 ISBN 1 844 32259 9 All rights reserved. No part of this document may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior permission of the Environment Agency. The views expressed in this document are not necessarily those of the Environment Agency. Its officers, servants or agents accept no liability whatsoever for any loss or damage arising from the interpretation or use of the information, or reliance upon views contained herein. Dissemination Status Internal: Released to Regions External: Released to Public Domain Statement of Use This manual contains management advice for trout, grayling and arctic char fishery managers. The information in this document is for use by EA staff and others involved in the management of fisheries in England and Wales. All fisheries are different and require individual consideration for the application of principles described in this Manual. Keywords Trout, grayling, Arctic char, management, fisheries, conservation. Research Contractor This document was produced under R&D Project W2-045 by: Dr Nick Giles & Associates, 50 Lake Road, Verwood, Dorset, BH31 6BX, UK. Tel: 01202 824245 Fax: 01202 828056 e-mail: [email protected] Environment Agency’s Project Manager The Environment Agency’s Project Manager for Project W2-045 was: Jeremy Westgarth, Environment Agency, Ghyll Mount, Gillan Way, Penrith Business Park, Penrith, Cumbria, CA11 9BP. R&D Technical Report W2-045/TR ii Version 1.0-02/04 Fisheries Technical Manual 7 Trout Fisheries Management Advice CONTENTS Page Contents iii List of Figures iv List of Tables vii Executive Summary ix Acknowledgements xii 1. Introduction 1 FISHERIES ECOLOGY 2. Trout Ecology 11 3. Grayling Ecology 35 4. Arctic Char Ecology 45 5. Feeding Ecology 57 WATER QUALITY AND QUANTITY 6. Water Quality 73 7. Water Quantity 95 FISHERIES MANAGEMENT 8. Habitat Quality And Improvement 105 9. Aquatic Plant Management 129 10. Conservation 151 11. Fishery Development 161 12. Land Drainage Consents 175 13. Screens And Obstructions To Fish Migration 181 14. Fisheries Socio-Economics 191 FISH STOCK MANAGEMENT 15. Stocking 199 16. Interactions Between Fish Species 229 17. Interactions With Other Species 239 18. Fish Diseases And Parasites 251 19. Poaching And Theft 265 20 Catch And Release Angling 273 R&D Technical Report W2-045/TR iii Version 1.0-02/04 Fisheries Technical Manual 7 Trout Fisheries Management Advice LIST OF FIGURES Figure 1 Brown trout......................................................................................................4 Figure 2 Grayling...........................................................................................................5 Figure 3 Arctic char .......................................................................................................6 Figure 4 'Blue' strain of rainbow trout ...........................................................................7 Figure 5 Brook trout (male above).................................................................................8 Figure 6 A ferox brown trout from Loch Garry, Scotland (3.6kg) ..............................11 Figure 7 The trout's life cycle (from EA, 1996; not to scale) ......................................12 Figure 8 The brown / sea trout.....................................................................................12 Figure 9 Examples of trout population 'bottlenecks' (EA, 1996).................................16 Figure 10 River Scorff, France, brown trout age distributions ......................................18 Figure 11 Long-term trout catch data from Llyn Conwy...............................................20 Figure 12 Angler's log book cover and example page...................................................22 Figure 13 Welsh sea trout fishery - long-term rod catch data........................................24 Figure 14 Inver fishery, Connemara, catch statistics .....................................................25 Figure 15 Salmo trutta smolt (above) and parr ..............................................................27 Figure 16 Smolt age composition for some English and Welsh sea trout rivers ...........27 Figure 17 Percentages of maiden sea trout first maturing at given sea ages .................28 Figure 18 Examples of trout scales ................................................................................29 Figure 19 Grayling.........................................................................................................35 Figure 20 A scale from a 3+ year-old grayling (River Wylye, Wiltshire).....................37 Figure 21 Arctic char .....................................................................................................45 Figure 22 Long-term Windermere char rod catches ......................................................49 Figure 23 Long term gill net CPUE for Windermere char ............................................51 Figure 24 Long term gill net and angler CPUE for Windermere char...........................51 Figure 25 Key stages of Mayfly life cycle.....................................................................57 Figure 26 Mayfly nymphs..............................................................................................57 Figure 27 Key stages of caddis fly life cycle .................................................................58 Figure 28 An upland trout stream ..................................................................................59 Figure 29 Chalk stream trout habitat..............................................................................62 Figure 30 Percentage of total energy intake for brown and rainbow trout from a small still water fishery represented by key food items ..........................................63 Figure 31 Lough Sheelin, Ireland - Pelagic trout diet....................................................64 Figure 32 Lough Sheelin, Ireland - littoral trout diet.....................................................64 Figure 33 Upland trout lake ...........................................................................................65 Figure 34 Llyn Tegid brown trout diet...........................................................................66 Figure 35 Percentage by volume Llyn Alaw brown trout diet.......................................66 Figure 36 Effects of pollution on downstream water quality.........................................78 Figure 37 Effects of pollution on distribution of animal species...................................79 Figure 38 Invertebrate samples from differing rivers (cleaner on left)..........................81 Figure 39 Aeration methods...........................................................................................89 Figure 40 Series of upstream 'V' current-deflectors scouring pools and stimulating Ranunculus growth on faster-flowing intervening riffles............................100 Figure 41 A mosaic of shade and sky-lighting on the River Piddle, Dorset................110 Figure 42 Correct coppicing practice........................................................................... 111 Figure 43 Erosion gulley in maize field - a source of extensive sediment inputs........ 112 Figure 44 A clear-watered, buffer-zoned tributary entering the main River Piddle that is silty with run-off from recently ploughed fields ......................................... 112 R&D Technical Report W2-045/TR iv Version 1.0-02/04 Fisheries Technical Manual 7 Trout Fisheries Management Advice Figure 45 Sheep-grazing bank erosion and fenced opposite bank with dense riparian vegetation..................................................................................................... 113 Figure 46 Wild trout fry densities on fenced and unfenced sections of the R. Piddle. 114 Figure 47 Wild trout parr and adult densities on fenced and unfenced sections of the River Piddle, Dorset .................................................................................... 114 Figure 48 Salmon parr densities on fenced and unfenced sections of the R. Piddle ... 114 Figure 49 Staked woven willow panels used to reinstated bank on this badly eroded river bend. The fencing will prevent livestock incursion ............................ 117 Figure 50 Channel narrowing creating a two-stage channel........................................ 117 Figure 51 Riffle placement .......................................................................................... 119 Figure 52 Excavating pools in a straight section stream.............................................. 119 Figure 53 Habitat improvement project using timber deflectors and marginal cover . 120 Figure 54 Bush providing cover over pool .................................................................. 120 Figure 55 Upstream V