Survival of juvenile European eels (Anguilla anguilla), transferred among salinities, and developmental shifts in their salinity preference

Authors

  • S. R. Crean,

    1. School of Biology and Biochemistry, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, U.K.
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  • J. T. A. Dick,

    Corresponding author
    1. School of Biology and Biochemistry, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, U.K.
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  • D. W. Evans,

    1. Environment and Heritage Service, Department of the Environment for Northern Ireland, Commonwealth House, 35 Castle Street, Belfast BT1 1GU, Northern Ireland, U.K.
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  • R. S. Rosell,

    1. Department of Agriculture and Rural Development for Northern Ireland, Newforge Lane, Malone Road, Belfast BT9 5PX, Northern Ireland, U.K.
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  • R. W. Elwood

    1. School of Biology and Biochemistry, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, U.K.
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All correspondence to: J. T. A. Dick, School of Biology and Biochemistry, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, U.K. E-mail: j.dick@qub.ac.uk

Abstract

After their oceanic migration, juvenile European eels Anguilla anguilla enter estuaries as glass eels, develop into pigmented elvers and migrate into fresh water. Fisheries often transfer such eels abruptly between salinities, principally glass eels and elvers from estuarine to fresh water. It is usually assumed that survival rates are high, but this required systematic investigation. Survival was found to be 100% over 21 days of glass eels and semi-pigmented elvers transferred abruptly from estuary conditions into fresh water, 50% sea water and full sea water. Fully pigmented elvers, however, showed significantly reduced survival when transferred into sea water. Salinity preference experiments with juvenile eels have historically been inconclusive. Here, in a choice chamber design, a clear developmental shift in salinity preference was found, with glass eels preferring 100% sea water, semi-pigmented elvers showing no clear preference and fully pigmented elvers preferring fresh water. We conclude that eel fisheries enhancement by abrupt transfer of juveniles among salinities is largely vindicated. In addition, developmental shifts in salinity preference have been clarified and this aids in the interpretation of eel migration patterns.

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