Research Document - 2011/075
Inter-laboratory verification of ageing consistency for Atlantic herring (Clupea harengus harengus) otoliths
By R. Miller, C. MacDougall, and J. Guerin
Abstract
An inter-laboratory verification of ageing consistency for Atlantic herring (Clupea harengus harengus) of the Gulf of St. Lawrence was undertaken by two laboratories, the Maurice Lamontagne Institute (MLI) in Mont-Joli (Quebec) and the Gulf Fisheries Center (GFC) in Moncton, (New Brunswick). The new primary age reader and the secondary age reader of MLI were compared with the highly experienced GFC age reader. The two laboratories aged a total of 200 whole otoliths from the 2010 commercial fishery conducted in the northern Gulf of St. Lawrence; half of the otoliths were from NAFO Division 4R and half from NAFO Division 4S.
Results are presented in terms of percentage agreement, total coefficient of variation (CV), Bowker’s test of symmetry, and age bias plots. The primary IML reader compared to the GFC reader resulted in 81.1% agreement with a CV of 2.05%. The secondary IML reader compared to the GFC reader yielded 66.5% agreement with a CV of 3.58%. The comparison of the two IML readers resulted in 71.8% agreement with a CV of 2.74%. In all three comparisons, Bowker’s test showed that there was no significant asymmetry. The levels of precision reflect the difficulty in the age determinations of these herring, being from catches in the summer and with a predominance of older fish.
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