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Evidence for a population collapse of European eel (Anguilla anguilla) in the Bristol Channel

Published online by Cambridge University Press:  30 August 2011

Peter A. Henderson ,
Shaun J. Plenty ,
Lyn C. Newton  and
David J. Bird
Peter A. Henderson*
Affiliation:
Pisces Conservation Ltd, IRC House, The Square, Pennington, Lymington, Hampshire, SO41 8GN, UK
Shaun J. Plenty
Affiliation:
School of Life Sciences, University of the West of England, Bristol, BS16 1QY, UK
Lyn C. Newton
Affiliation:
School of Life Sciences, University of the West of England, Bristol, BS16 1QY, UK
David J. Bird
Affiliation:
School of Life Sciences, University of the West of England, Bristol, BS16 1QY, UK
*
Correspondence should be addressed to: P.A. Henderson, Pisces Conservation Ltd, IRC House, The Square, Pennington, Lymington, Hampshire SO41 8GN, UK email: peter@pisces-conservation.com
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Abstract

A 30-year study of the estuarine population of yellow eel, Anguilla anguilla, abundance in Bridgwater Bay, Somerset, UK, shows that the population number has collapsed. Since 1980, the decline has averaged 15% per year. The abundance of eel in 2009 is estimated at only 1% of that in 1980. This is one of the greatest systematically quantified crashes of a fish population ever reported. Collections of eels impinged on cooling water filter screens were made monthly at Hinkley Point power station between 1980 and 2010 and from Oldbury power station between 1996 and 1998. Eels are always present in the Severn Estuary, although there are large seasonal variations in abundance. At Oldbury, in the upper estuary, eels are least abundant in January. In contrast, in the outer estuary in Bridgwater Bay, eels are most abundant between November and March. The size-distribution of yellow eels ranged from <200 to >700 mm indicating an age-range since the glass eel stage of 2 to >25 years. The mean size-range has not changed since the 1980s indicating that the population collapse is not caused by a sudden recruitment failure. It is suggested that there has been a continual long-term failure of recruitment to compensate for losses. The reason for this is unidentified, but is unlikely to be changes in the North Atlantic Oscillation or other natural environmental variability. A major effort to improve eel survival to adulthood is required if this species is not to gently fade to extinction. This would likely involve a cessation of elver fishing, a reduction in the volume of estuarine water extracted for power station cooling and other purposes during which eels are entrained and killed, and the removal of obstructions which increase mortality during migration.

Keywords

eel population declinelong-term samplingNorth Atlantic Oscillation Indexpower station monitoringsalinityseasonal variationwater temperature
Type
Research Article
Information
Journal of the Marine Biological Association of the United Kingdom , Volume 92 , Issue 4: Coral Reefs, the Aquarium Trade and the Maritime Industry , June 2012 , pp. 843 - 851
Copyright
Copyright © Marine Biological Association of the United Kingdom 2011

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