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Validation of scale‐age determination in European grayling Thymallus thymallus using tag‐recapture analysis
Author(s) -
Horká P.,
Ibbotson A.,
Jones J. I.,
Cove R. J.,
Scott L. J.
Publication year - 2010
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.2010.02664.x
Subject(s) - grayling , biology , mark and recapture , fishery , population , fish <actinopterygii> , ecology , demography , sociology
To validate age determination from scales in European grayling Thymallus thymallus , the scale‐read age of fish was compared with the true age obtained by tag‐recapture analysis. A total of 3997 individuals were tagged with visible implant tags and passive integrated transponder (PIT) tags in the River Wylye, south‐west England during 1999–2007. Annual repeat surveys were undertaken and collected scales read without prior knowledge of tag‐recapture age. Accuracy of fish ageing by scales was highest in 1 and 2 year‐old fish but decreased in older fish. In later life stages (>4 years old), underestimation of age occurred and the error in reading scales rose to 51·9% in 5 year‐old fish. Age assigned from scales underestimated the tag‐recapture assigned age by as much as 3 years. This study suggests that use of scales is an appropriate method to age a short‐lived population of T. thymallus inhabiting productive lotic systems. The underestimation of age in older fish, however, needs to be considered in the management of fish stocks because it may lead to undesirable exploitation of population.