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Are scales suitable structures for ageing largemouth bass Micropterus salmoides in South Africa?

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Author(s): Geraldine Claire Taylor

Journal: African Zoology
ISSN 1562-7020

Volume: 47;
Issue: 2;
Date: 2013;
Original page

Keywords: sagittal | otoliths | precision | growth zones | APE | comparison

ABSTRACT
The suitability of scales for ageing Micropterus salmoides was determined by comparing the precision of growth zone counts on scales with those obtained from sectioned sagittal otoliths from a sample of 496 fish collected in the Eastern Cape, South Africa. Otoliths (1.2% rejected) were more readable than scales (31% rejected). Otolith readings were more precise (average percentage error (APE) = 13.6%; coefficient of variation (C.V.) = 15.8%) than scales (APE = 18.0%; C.V. = 21.9%). Growth zone counts between structures were not symmetrically distributed around the agreed ages (otolith age = scale age) of the fish (Bowker’s test H2: χ2 = 149, df =28, p < 0.05) and graphical comparison showed that scales tended to underestimate age, particularly for fish older than 5 years. Scales are therefore not suitable structures for ageing South African M. salmoides which may attain ages of up to 13 years.
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