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

Geometric mean regression analysis between log(length) and log(height) of o toliths from lake trout (Salvelinus namaycush) from six lakes revealed that the growth of this structure was negatively allometric, indicating that ot olith shape varies throughout the life of the fish. Otolith shape was quant ified using harmonic amplitudes 2-10 (A(2)-A(10)) extracted from Fourier-se ries analyses. We found harmonic amplitudes 2 (A(2)) and 5 (A(5)) to be ass ociated with the length/height relationship. Some recent studies have sugge sted that growth of fish otoliths affects their shape. Our results indicate that part of this otolith-growth effect could be due to an intrinsic chang e in shape associated with allometric nature of the length/height relations hip. There were no differences in otolith shape between males and females. Otolith shape was also compared among the six populations. Major difference s were observed between Lake Normand (Saint Maurice River watershed) and th e five lakes in the Ottawa River watershed, suggesting that genotype could be an important factor affecting otolith shape. The percentage of reclassif ication using a discriminant function analysis was high (86%) for the Lake Normand population. Among populations from the Ottawa River watershed, diff erences in otolith shape were more subtle, with reclassification percentage s ranging from 50 to 75%. However, one population in the Ottawa River water shed (Lake Duval), which was introduced as hatchery-raised individuals, dif fered slightly from the other populations from the same watershed, includin g Lake Trente et un Milles, from which it originated.