Fluctuating asymmetry in the otoliths of larval Atlantic menhaden Brevoortia tyrannus (Latrobe) – a condition indicator?
Fluctuating asymmetry (FA) was described for otolith length, width and area for two groups of larval and juvenile Atlantic menhaden Brevoortia tyrannus. The larvae and juveniles (age range: 20–120 days; standard length, LS, range: 14–35 mm) were separated into the two distinct groups a priori on the basis of their growth indices estimated from residuals of a LS-at-age model; slow growers had residuals <8% of the average size at age and fast growers had residuals >8%. Some indication supporting the fluctuating asymmetry methodology was found when unsigned normalized FA2 index was used for otolith area. That conclusion was not, however, supported by the other method used in this work, i.e. between-group ANCOVA analysis of individual unsigned and not normalized FA1 indices plotted against trait size. These inconsistent results are most probably a consequence of error introduced during FA index normalization (accounting for trait size effect on absolute FA). Although it is concluded here that FA analysis of sagittal otoliths was not effective in describing differences in the natural variability of growth and condition of larval Atlantic menhaden, the possible species- and otolith type-related differences should be considered in the future research on FA.
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