Trout stocking in SAC rivers. Phase 1: Review of stocking practice Science Report: SC030211/SR1 SCHO0707BMZC-E-P The Environment Agency is the leading public body protecting and improving the environment in England and Wales. It’s our job to make sure that air, land and water are looked after by everyone in today’s society, so that tomorrow’s generations inherit a cleaner, healthier world. Our work includes tackling flooding and pollution incidents, reducing industry’s impacts on the environment, cleaning up rivers, coastal waters and contaminated land, and improving wildlife habitats. This report is the result of research commissioned and funded by the Environment Agency (Habitats Directive Programme), English Nature and the Countryside Council for Wales. Published by: Author: Environment Agency, Rio House, Waterside Drive, Aztec West, N. Giles Almondsbury, Bristol, BS32 4UD Tel: 01454 624400 Fax: 01454 624409 Dissemination Status: www.environment-agency.gov.uk Publicly available ISBN: 978-1-84432-796-6 Keywords: Trout, stocking, cSAC rivers, salmon, bullhead, crayfish © Environment Agency July 2007 Research Contractor: All rights reserved. This document may be reproduced with prior Dr Nick Giles & Associates, permission of the Environment Agency. 50 Lake Road, Verwood, Dorset, BH31 6BX. The views expressed in this document are not necessarily Tel: 01202 824245 those of the Environment Agency. Email: [email protected] This report is printed on Cyclus Print, a 100% recycled stock, Environment Agency’s Project Manager: which is 100% post consumer waste and is totally chlorine free. Miran Aprahamian, Richard Fairclough House, Warrington Water used is treated and in most cases returned to source in better condition than removed. 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Phase 1: Review of stocking practice iii Executive summary This report describes the first phase of a project to provide a decision-making framework for Environment Agency, English Nature and Countryside Council for Wales staff for the assessment of Section 30 consents to stock trout into candidate Special Area of Conservation (cSAC) rivers. A literature review and its interpretation is given along with the findings of an earlier report (APEM, 2002) to English Nature. Key potential ecological interactions between stocked brown and rainbow trout and cSAC species involve those with Atlantic salmon (competition from juvenile trout, predation by adult trout and, possibly, hybridisation between these species), white-clawed crayfish (possible disease transmission and predation by adult trout) and bullheads (predation by adult trout and, possibly, competition for resources). The selected rivers for study are briefly described on the basis of their cSAC designations. Information collected from riparian managers and from the Environment Agency Live Fish Movements Database is then given on recent trout stocking activity in these rivers. The key findings of this report are that trout stocking is relatively infrequent in six of the cSAC river systems studied (Eden, Yorkshire Derwent and Rye, Dove and Lathkill, Teifi, Wye and Usk). Because of this, important ecological interactions resulting from stocking are unlikely to occur except, possibly, via disease transmission (crayfish plague) to native crayfish populations. In order to reduce risks, close liaison between the Centre for Environment, Fisheries and Aquaculture Science (CEFAS, fish farm trout movements) and the Environment Agency, English Nature and Countryside Council for Wales (Section 30 consenting) is recommended. On the rivers Itchen and Hampshire Avon, relatively large numbers of trout are stocked into areas where Atlantic salmon spawn. In 2003, the Itchen salmon stock reached only 23 per cent of its conservation limit and the Hampshire Avon reached only 30 per cent. More research is needed to investigate whether trout stocking is likely to be a significant factor in depressing wild salmon abundance in these rivers. Initial analyses of trout catch records for the rivers Itchen, Nadder and Wylye show how catches relate to some extent to the timing of stocking and how trout fishery performance is finely regulated by managers. More information on typical trout residence times is needed. Recommendations for Phase 2 of the study include analyses of electric fishing data and published reports to establish: • expected densities of brown trout in rivers; • actual densities of trout generated in rivers after stocking; • whether the stocked trout remain resident in habitat areas used by juvenile salmon and how long stocked trout typically survive within fisheries; • the expected size ranges of stocked and natural trout stocks in rivers. iv Trout stocking in SAC rivers. Phase 1: Review of stocking practice Contents 1. Introduction 1 2. Literature review: potential impacts of stocked trout on SAC species 2 2.1 The APEM report 2 2.2 The present study 6 2.3 Interactions of Atlantic salmon with rainbow and brown trout 6 2.4 Interactions of pearl mussel with rainbow and brown trout 13 2.5 Interactions of bullhead with rainbow and brown trout 14 2.6 Interactions of crayfish with rainbow and brown trout 15 2.7 Interactions of lampreys with rainbow and brown trout 17 3. CSAC river designations and trout stocking activity 18 3.1 Rivers selected for this study 18 3.2 Stocking of trout in SAC rivers in the study 18 3.3 Locations, cSAC designations and stocking information for study rivers 22 4. Residence time of stocked trout 53 4.1 Trout stocking and residence in fisheries 53 4.2 Persistence of stocked trout 54 4.3 Analysis of trout rod catch data collected in this study 57 5. Conclusions 67 6. References 68 Trout stocking in SAC rivers. Phase 1: Review of stocking practice v 1 Introduction This report describes the first phase of a project to provide a decision-making framework for Environment Agency, English Nature and Countryside Council for Wales (CCW) staff for the assessment of Section 30 consents to stock trout in candidate Special Area of Conservation (cSAC) rivers. The report provides a literature review and interpretation of the potential ecological impacts on certain riverine SAC species of stocking with brown and/or rainbow trout, along with information on trout stocking and trout residence in fisheries. Firstly, the literature review and interpretation is compared with the findings of a previous unpublished report to English Nature (APEM, 2002). Next, the selected rivers for study are briefly described on the basis of their cSAC designations. Information on recent trout stocking activity in these rivers, collected from riparian owners/managers and from the Environment Agency Live Fish Movements Database (LFMD), is also given. Initial analyses of trout catch records are then used to further explore methods of stocking and possible residence times for stocked trout. Finally, the report presents its conclusions and recommendations for Phase 2 of the study. Trout stocking in SAC rivers. Phase 1: Review of stocking practice 1 2 Literature review: potential impacts of stocked trout on SAC species This review builds upon the unpublished review by APEM (2002) and covers brown and rainbow trout interactions with certain Special Area of Conservation (SAC) species, especially salmon, crayfish, bullhead and lampreys. 2.1 The APEM report The APEM (2002) report to English Nature identified risks to SAC species associated with introductions of various fish species, summarised in Table 3.1 in the 2002 report. The table is reproduced below (Table 2.1). 2 Trout stocking in SAC rivers. Phase 1: Review of stocking practice Table 2.1: Sensitivity table for fish introductions (SAC species) (from Table 3.1, APEM 2002). SAC SAC SAC Species species site group Predation on fish, Predation amphibia inverts., with Competition fish indigenous species with Hybridisation fish indigenous effect Detrimental on overall ecology of Introduction