The Distribution, Biology and Ecology of Shad in South-West England
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The Distribution, Biology and Ecology of Shad in South-West England R&D Technical Report W1-047/TR Robert Hillman Research Contractor Environment Agency 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 2003 ISBN: 1 84432 103 7 This report is the result of work jointly funded by the Environment Agency and English Nature All rights reserved. No part of this document may be produced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without prior permission of the Environment Agency and English Nature. The views expressed in this document are not necessarily those of the Environment Agency. Its officers, servant 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: Public Domain Statement of Use This report presents the findings from a 2 year collaborative project, between the Environment Agency and English Nature, studying the distribution, biology and ecology of shad (Alosa sp) in the Environment Agency’s south-west region. Through this study a successful survey methodology for shad has been designed. This has led to changes in our understanding of shad ecology and distribution in the South West region. The conclusions and recommendations provide essential guidance and information for similar projects. Keywords Allis shad, Twaite shad, Alosa alosa, Alosa fallax Research Contractor This document was produced under R&D Project W1-047 by: Environment Agency, Guildborne House, Chatsworth Road, Worting, West Sussex BN11 1LD Tel: 01903 832000 Fax: 01903 214950 Environment Agency Project Manager The Environment Agency's Project Manager for R&D Project W1-047 was: Paul Smith, Southern Region. Further copies of this report are available from: Environment Agency R&D Dissemination Centre, c/o WRc, Frankland Road, Swindon, Wilts SN5 8YF Tel: 01793-865000 Fax: 01793-514562 e-mail:[email protected] R&D TECHNICAL REPORT W1-047/TR ACKNOWLEDGEMENTS Thanks to Paul Smith (Project Manager) and Pamela Mardon (R&D Technical Support). Thanks to all those who helped with the project and those who assisted with the project reports. Of the former, thanks go to the netsmen on the estuaries of the Camel, Dart, Exe, Fowey, Tamar and Torridge, especially to Roger and Steven Tabb, Alan Jewitt, Colin Matthews, Alec Scoble, Barry Sockell and Derek Barnes. Thanks also to the many people who took the trouble to contact me with records or fish, notably Douglas Herdson, Danny Poulding, David Jenkins and Philip Marshall. For assistance with fieldwork and laboratory work, thanks to Derek Goodwin, Donovan Kelly, Pippa Caswell, Paul Elsmere, Plymouth Marine Laboratory and Adrian Brown. Thanks to Alan Henshaw at the Environment Agency fish hatchery, Calverton, for help in hatching, rearing and identifying shad eggs. For providing technical advice and guidance on the project reports, thanks to Miran Aprahamian, Mike Pawson, David Fraser, Tristan Hatton-Ellis, Phil Hickley, Willie Yeomans, Simon Toms, Andy Strevens, Rob Wood, Adam Fraser and Marina Flamank. R&D TECHNICAL REPORT W1-047/TR i EXECUTIVE SUMMARY Allis (Alosa alosa) and twaite shad (Alosa fallax) occur throughout Europe, but in recent years the population of both species has declined. This has been attributed primarily to; • poor water quality; • low water flows; • habitat destruction or degradation and, • the construction of large navigation weirs that hinder shad access to spawning grounds. There is a lack of information about the distribution and spawning status of allis and twaite shad in the United Kingdom, although evidence suggests there may be spawning populations, particularly in south-west England. In the South West shad have been recorded from estuaries and notably, adult allis shad from the River Tamar, highlighting the need to investigate both species in the area. This Research and Development project, concentrating in south-west England, is intended to be used as a template for the investigation of shad in other Environment Agency regions. The Environment Agency is a lead partner in the Biodiversity Species Action Plan (BAP) for both shad species and has therefore signed up to specific actions. This project aimed to deliver some of the actions attributed to the Environment Agency, in particular to investigate the current population and spawning status of shad and to develop species monitoring and management plans. Specific project tasks included the approach of potential project partners and useful sources of information, and the assembly of information on shad distribution, biology, ecology and similar studies. Allis and twaite shad were studied in the marine phase, mainly through recording commercial by catches of shad in trawls and examining specimens. Studying the shad freshwater migration phase involved liasing with salmon netsmen and river anglers, as well as using video footage from fish counters. Catches were recorded and specimens examined, where available. Assessment of spawning habitat and surveys for shad eggs and juveniles were also undertaken if records (e.g. video counter) indicated shad had moved into freshwater. A wide range of potential project partners were contacted, including DEFRA and Sea Fisheries Officers, nature conservation organisations, marine zoological research organisations, information and record centres, angling clubs, fishing tackle shops, commercial fishermen, salmon netsmen, fish wholesalers/auctioneers and fishmongers. A poster and recording form were designed and distributed, including project information, to a range of people from the groups listed above. The project was also promoted through the media, in press, by radio and on television. People were encouraged to contact the Agency with records of shad catches, or in the case of commercial fishermen, with specimens of shad caught as a by catch. The sex, stomach contents, parasites and sexual condition of specimens was recorded, and measurements/counts were made of certain biological characters, such as total body length, body weight and number of gill rakers on the first gill arch. Age-class and spawning history was estimated using fish scales. In the marine phase twaite shad were recorded at approximately twice the frequency of allis shad. Both shad species were distributed all around the South West coast, R&D TECHNICAL REPORT W1-047/TR ii particularly along the south coast, although this may reflect a greater fishing effort on the south coast compared to the north. Anecdotal evidence suggests that catches of shad at sea were significantly greater during 2000 than in previous years; occasionally catches of up to one and a half tonnes of shad were made off the coast of south-west England. Allis and twaite shad were usually caught in trawls and were most abundant during the winter months offshore of Lands End, Looe and Plymouth (South-east Cornwall), Torbay (South Devon) and Lyme Bay (South Dorset). Significant numbers of records also came from fishermen using inshore bass and gill nets. Although twaite shad were the commoner species at sea, allis shad were recorded far more frequently than twaite from estuaries in the South West. Most records of shad caught during their freshwater phase came from salmon netsmen. Adults of both species were recorded from the Exe and Torridge estuaries in Devon. Adult allis shad were also recorded from the Tamar and Fowey estuaries in Cornwall, with anecdotal reports describing catches in the estuaries of the Camel, Fal/Helford and Lynher, Cornwall, and the Dart Estuary, Devon. Immature allis shad were recorded from the Camel, Fal/Helford and Fowey estuaries in Cornwall, and from the Dart and Kingsbridge estuaries in Devon. Shad were observed migrating upstream on video footage taken at Gunnislake Fish Pass on the River Tamar. Gunnislake Weir forms an artificial boundary between fresh and salt water, previously considered to be impassable to shad. Anglers caught adult allis shad in spawning condition as far as fifteen miles above the tidal limit in the River Tamar. Additionally, salmon netsmen in the Tamar, Fowey and Torridge estuaries caught adult allis shad in spawning condition and in June 2001, two spent males were caught in the Tamar Estuary. Although twaite shad were caught from the Torridge and Exe estuaries, fish in spawning condition were only caught from coastal waters. Seine netting was carried out in the Camel, Tamar, Helford and Fal estuaries from May until September 2000 (No juvenile shad were found; sample methods, sites and conditions were designed to catch juvenile bass). A one-day survey of the Tamar Estuary at Holes Hole (National Grid Reference SX 428653), in August 2001, also failed to detect juvenile shad. River Habitat Survey (RHS) methodology was used to determine likely spawning habitat on the River Tamar. Surveys for shad eggs were carried out in the River Tamar and upper Tamar Estuary from June until August 2000, using kick-sampling methods. Shad eggs were found at one site immediately below Gunnislake weir (National Grid Reference SX 436712). This site was similar to descriptions of shad spawning sites on rivers with known populations. The eggs were identified as alosid by staff at the Agency Fish Hatchery, and strongly