Determining the effect of negative allometry (length/height relationship) on variation in otolith shape in lake trout (Salvelinus namaycush), using Fourier-series analysis

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Geometric mean regression analysis between log(length) and log(height) of otoliths from lake trout (Salvelinus namaycush) from six lakes revealed that the growth of this structure was negatively allometric, indicating that otolith shape varies throughout the life of the fish. Otolith shape was quantified using harmonic amplitudes 2-10 (A2-A10) extracted from Fourier-series analyses. We found harmonic amplitudes 2 (A2) and 5 (A5) to be associated with the length/height relationship. Some recent studies have suggested that growth of fish otoliths affects their shape. Our results indicate that part of this otolith-growth effect could be due to an intrinsic change in shape associated with allometric nature of the length/height relationship. There were no differences in otolith shape between males and females. Otolith shape was also compared among the six populations. Major differences were observed between Lake Normand (Saint Maurice River watershed) and the five lakes in the Ottawa River watershed, suggesting that genotype could be an important factor affecting otolith shape. The percentage of reclassification using a discriminant function analysis was high (86%) for the Lake Normand population. Among populations from the Ottawa River watershed, differences in otolith shape were more subtle, with reclassification percentages ranging from 50 to 75%. However, one population in the Ottawa River watershed (Lake Duval), which was introduced as hatchery-raised individuals, differed slightly from the other populations from the same watershed, including Lake Trente et un Milles, from which it originated.