Sex-Specific Life History Affected by Stocking in Juvenile Brown Trout

Salmonids are a socioeconomically and ecologically important group of fish that often managed by stocking. Little is known about potential sex-specific effects stocking, but recent studies found the sexes differ in their stress tolerances already at late embryonic stage, i.e., before hatchery-born larvae released into wild long morphological gonad formation. It has also been speculated life histories can affect juvenile growth mortality, resulting sex-biassed demography reduce population growth. Here we test whether brown trout ( Salmo trutta ) show such sex hatchery- wild-born fish. We modified genetic sexing protocol to false assignment rates used it study timing differentiation laboratory setting, large-scale field experiment mortality different environments. no any environments studied. However, females started earlier than males, while were similar laboratory, they differed significantly depending on location origin Overall, males grew larger showed reverse pattern. Whether or was location-specific. conclude affected stocking other environmental factors remain be identified.