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Sexual Dimorphism in Growth of Freshwater Drum

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Rypel, Andrew L.


I examined sexual dimorphism in the long-lived Aplodinotus grunniens (freshwater drum) from five lakes and four rivers in Alabama. Using the Von Bertalanffy growth function combined with nonparametric statistics, I found males and females had similar annual growth rates from years 0–4 years of age, but then showed significantly different growth rates across subsequent ages. Female drum grew significantly faster through adulthood, and ultimately attained significantly larger sizes (L∞ = 510.8 mm, TL) compared to males (L∞ = 385.3 mm, TL). This study highlights the difference gender can have in evaluation and interpretation of population characteristics, especially for long-lived and highly fecund fishes such as freshwater drum.