Analysis and Comparison of Fish Growth from Small Samples of Length-at-Age Data: Detection of Sexual Dimorphism in Eurasian Perch as an Example

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Abstract
A relatively simple approach is presented for statistical analysis and comparison of fish growth patterns inferred from size-at-age data. It can be used for any growth model and small sample sizes. Bootstrapping is used to generate confidence regions for the model parameters and for size and growth rate at age. Significance of differences between growth patterns is tested with a likelihood ratio test, the validity of which was confirmed by Monte Carlo simulations. As an illustration of the applicability of this approach, we analyzed a set of length-at-age data on female (N = 57) and male (N = 27) Eurasian perch Perca fluviatilis from a shallow, eutrophic Dutch lake, Tjeukemeer. We used the von Bertalanffy growth curve to model length at age for both sexes separately. This analysis showed a significant difference in length between males and females between age 2 and age 6, with females being larger. At older ages the confidence regions became too wide to detect sexual dimorphism. The applicability...

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